Download c) High Rupturing Capacity (HRC) Fuses

Section – Two
Electrical Specification
Part – 2
General Electrical Specification
2/0
Section – Two
Electrical Specification
Part – 2
General Electrical Specification
Part -2
GENERAL ELECTRICAL SPECIFICATION
1.0
BASIC DESIGN
a.
1.01
The equipment should be capable of operations under local ambient conditions.
REFERENCES
a.
Conform to Section 16010 - Electrical - General Requirements.
b.
Codes :
ACB/MCCB
BSEN 60947-2&3,
BS 3871 part-II, BS 4752
BS 60439 part-I
Switch board
Switchboard degree of
Protection
Degree of protection
ELCB/RCCB
MCC
Distribution Boards
Starters and Control
Gears
Electrical Motors
Motor Insulation
Fans
Pumps
Control Panel Indication
Lamps
Bus Bars
PVC insulated wiring cables
Non armoured 450/750
Grade
PVC insulated Steel wire
Armoured PVC sheathed Cables
600/1000V grade
XLPE insulated steel wire
Armoured PVC sheathed multicore
Cables 600/1000V grade
BS 5490
BS 5420
BSEN 61008, BS 4293
BS 5486
BS 5486, BS 4649
BS 5486
BS 4999, BS 5000
BS 2757
BS 848 part I & II
BS 599
BS 4099
BS 158, BS 159
BS 6004
BS 6346
BS 5467
XLPE insulated Aluminium wire
Armoured PVC sheathed single
Core cables
Jointing Tapes
MICC cables
BS 5467
BSS 633, BSS 3924
BS 6207.1987
2/1
Section – Two
Electrical Specification
Part – 2
General Electrical Specification
Fire resistant cables
Flexible Cables
Cables for general lighting &
Luminaires
Cable trays
Switches
Switch socket outlets
GI boxes
DP switches/fuse conn. Units
Cooker Control Units
Cable Glands
Lamp holders
Steel trunking
Cables & MICC fittings
Isolating transformers
Ceiling roses
Protection against corrosion
Single pole switches
Distribution Units for
Building sites
Distribution of Electricity
For Building sites
Earthing and Lightning
Protections
BS 4066 part-I, BS 6360, BS 6899, BS 7629.1993
BS 6004
BS 4533
BS 729
BS 3676
BS 1363, BS 546
BS 4662
BS 5733,BS 3676, BS 1362
BS 4177
BS 4121
BS 98
BS 4678
BS 4081
BS 3535
BS 67
BS 1706
BS 3676
BS 4363
CP 1017
BS 6651 1992
1.02
MATERIALS
a.
Materials shall be new, of local manufacture where available, first quality and uniform throughout.
Submit tender based on the use of materials and equipment specified.
b.
Electrical materials shall be DEWA approved and be so labelled. Material not DEWA approved shall
receive acceptance for installation by DEWA before delivery, and modifications and charges
required for such acceptance shall be included in work of this Section. Material shall not be installed
or connected to the source of electrical power until approval is obtained.
c.
Confirm capacity, ratings and characteristics of equipment items being provided to supply power to
equipment provided under other Sections of the work. Resolve discrepancies before such items are
purchased.
1.03
MATERIAL ACCEPTANCE
a.
Acceptance of materials installed presumes that materials have not been damaged or exposed to
conditions that would adversely affect performance and life expectancy.
1.04
RACEWAYS
a.
Rigid galvanized steel conduit shall comply with BS4568 Class 4.
b.
Rigid PVC conduit shall comply with BS4607 Part 1.
2/2
Section – Two
Electrical Specification
Part – 2
General Electrical Specification
1.05
WIRE & CABLE
a.
Wire and cable shall comprise copper conductors, sized as noted, rated 75 deg. C., 600 volt
minimum, flame retardant insulation, and DEWA approved for application.
b.
Wire and cable installed in conduit shall be PVC insulated Type TWH - Flame retardant and comply
with BS Specification.
c.
Cabling will be as detailed on the drawings.
d.
All cable must be by an approved manufacturer.
e.
The Contractor shall be responsible for ascertaining the lengths of all cable covered by the
specification.
f.
All conductors of paper-insulated cables shall be shaped and bedded and suitable for an earthed
system.
g.
All cable and conductors shall be copper unless otherwise specified.
1.06
DEVICES
a.
Wiring devices unless otherwise specified herein, or noted, shall be as manufactured by approved
manufacturer like MK, Crabtree, etc.
b.
Time switches shall be of types noted on the drawings.
1.07
DEVICE SPECIALIZED
a.
Contactors controlling lighting loads shall be enclosed mechanically held, electrically operated, in
suitable enclosure of the sizes and types indicated. Contactors shall be complete with coil clearing
contacts and control transformers as necessary for control by time switch (or pushbutton) as
specified and detailed.
1.08
DEVICE COVER PLATES
a.
Switch and receptacle and other device faceplates for flush mounted devices, generally shall be
single or multi-gang as required with removable protective covering.
b.
The finish of cover plates shall be white plastic as approved by the engineer/architect.
c.
The local switches shall be 20 amp type. Circuit switches shall be one-way, two-way, intermediate
or double pole as indicated on the drawings. Where more than one switch is indicated at any
position multiple gang units shall be used with 500V phase barrier inside.4 Switches shall be of the
quick start make, slow break type specially designed for AC circuits.
d.
For flush mounting switches the switch-plate shall overlap all edges of the box by not less than 7mm.
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Section – Two
Electrical Specification
Part – 2
General Electrical Specification
For surface mounting switches the switch plate shall finish flush with the edges of the switch boxes.
Switches for water heaters and fan coil units shall be 20 amp, double pole type, complete with neon
indicator lights and engravings the purpose/usage.
e.
In plant rooms the switch units shall be surface or flush as required.
f.
Local switches shall be arranged in convenient positions for switching the various circuits and
generally as indicated on the drawings.
g.
Weatherproof enclosures for outdoor receptacles shall be approved equal, gasketted double lift
cover.
h.
Cover plates for other devices such as flush fan controls, telephone, etc., shall be as per Engineer’s
approval and shall match in colour with the adjascent electrical cover plate.
i.
The switch socket outlets, shall be as indicated on the drawings, all in accordance with as
appropriate.
j.
Sockets more than 3 nos. shall be connected in ring circuits.
k.
The switch socket outlets shall be assembled in single or multiple units in G.I boxes. All boxes shall
be supplied with adjustable steel grids and earthing terminals.
l.
Telephone outlets shall be flush mounted type. These shall be of the same make and finish of the
adjacent socket outlets. Master and slave tel. Socket shall be installed as per Telephone Department
(ETISALAT) requirements.
m.
Back boxes to be provided with brass earth terminal to facilitate earth wire connection. The boxes to
have sufficient number of 20mm and 25mm knockout and shall comply with relevant codes. Boxes
to have adjustable lug for proper installations of wiring accessories. Extension ring to be used along
with G.I boxes, in places where the box is deep inside the wall, marble or concrete.
n.
DP Switches shall be of flush or surface mounting type. The fuse connection units shall incorporate
integral switch, neon indicator and 13A fuse links. When the 20A DP switches are used to connect
air handling units and water heaters, these shall be supplied with an integral switch and a flexible
outlet. These shall be of the same manufacturer for a particular type of switch throughout the
installation and shall be complete with the other accessories installed. The choice of plate finishes
will be in accordance with the Engineer’s instructions.
o.
Mounting Heights: The mounting heights for the electrical equipments and accessories shall be coordinated equipment layout and shall be as per site requirements. Engineer’s approval shall be taken
before starting fixing of the back boxes. The following heights may be followed for general purpose:
a)
b)
c)
d)
e)
Switches and fire alarm Break glass
Switch socket outlets/telephone/
TV outlets
Fire Alarm Control Panel/DBs
Isolators for FCU
Flexible outlet for Water Heater/
: 1300mm FFL
: 400mm FFL
: 1800mm FFL
: Near Unit
2/4
Section – Two
Electrical Specification
f)
1.09
Part – 2
General Electrical Specification
Other equipments
Isolators/DP Switch for Hand Driers
: Near Unit
Above false ceiling
PANELBOARDS
a) Switchboards
1.
Switchboards shall be manufactured, factory assembled and tested by a specialist
switchboard manufacturer, shall be identical in mechanical construction, except where
modified by this Specification, to the manufacturer’s standard range which shall have been
type-tested by a competent testing authority (ASTA) to the fault conditions specified.
Evidence of compliance with the above requirements, including maker’s literature, a list of
contracts successfully completed for similar switchboards, and copies of test certificates,
shall be submitted.
Flush fronted switchboards are generally required and they shall be of cubicle type
construction, self supporting, with cubicle top, side panels and doors at least 1.5mm thick
sheet steel on frame having members at least 2.5mm thick give a rigid construction without
cross struts.
Each switchboard shall be of uniform height and depth front to back,
throughout its length. All hinges shall be of concealed type. Each switchboard shall have
circuit-breakers/MCCBs and fuse switches arranged in tier formation with removable front
access panels and bolted back plates and copper bus bars suitably shrouded.
Each switchboard shall, where specified, include a 100 mm channel iron plinth. If not
specified any where else, the construction of switch board shall be form IV.
2.
Industrial type switchboards, where specified, shall be suitable for floor mounting. They
shall be constructed of angle iron which shall be arranged to support all items of equipment.
The switchboard shall comprise an incoming switch feeding onto a four pole busbar
chamber, and MCCBs/fuses switches/ Circuit breakers controlling outgoing circuits
mounted above and below. All interconnecting cables and trunking, labels, cable boxes and
glands shall be included. The framing shall be painted with two coats of aluminum paint on
completion. The contractor shall provide suitable testing equipment on site and carry out
applied voltage tests.
Each switchboard shall incorporate storage facilities for spare fuses.
Each switchboard shall have the current rating specified. All fuse-switches/ Circuit breakers
shall be complete with high breaking capacity of not less than the associated switchgear. A
spare set of fuses shall be housed inside the cover of each fuse-switch. Fuse switches shall
be equipped with either cable box, gland and cable gland or conduit entry. A copper earth
bar shall be bolted to the main switchboard frame.
3.
All switchboards and fuse-switches shall be dust tight and the metal work must be finished
to withstand local climatic conditions. All lids and removable panels shall be fitted with
suitable gasket to prevent the ingress of moisture and insects. All units shall include locking
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Section – Two
Electrical Specification
Part – 2
General Electrical Specification
devices.
An ammeter , voltmeter and an energy meter shall be provided suitable scaled on the main
incoming switch of each switchboard. Each meter shall be provided complete with a phase
selector and off switch so that readings of all phases may be obtained including voltage
between phases.
The Contractor shall confirm with the switch board manufacturers that the switchboards are
complete with all cable boxes, meters and ancillary equipment before the switchboards are
certified completed for despatch at the manufacturer’s works, as no claims for variations will
be estimated due to inadequate provisions being made. All switchgear shall be clearly
labelled to indicated its position and purpose. The housing as well as all the components of
the switchboard shall be as per the list of approved make.
Main busbar joints shall be achieved using threaded busbar rather than fully bolted joints.
4.
Drawings of all switchboards to a scale not less than 1:10 shall be submitted by the
Contractor, for the approval of the Engineer, prior to commencement of manufacture. In
order to minimize delay in the preparation of working drawings for approval, the Contractor,
at the time of ordering the switchboards, shall aquatint the manufacturer with full details of
the areas available in switch rooms and plant rooms, together with the proposed routes and
details of all incoming and outgoing cables relative to switchboard entry.
Layout of switchgear on the drawings is diagrammatic only.
Busbars shall be 98% pure electrolytic copper and shall run horizontally and shall contain
triple phase and neutral busbars rated as shown on the drawings or specified elsewhere, of
hard drawn high conductivity copper. Bus bars shall confirm to relevant DEWA codes.
5.
The switchboard cubicles shall be solidly bonded by one continuous copper earth bar
throughout the entire length of the switchboard. Provisions shall be made at the end of the
bar for connection to the main earthing system. The main earth bar, or tee-off connection
shall be located convenient to the cable gland plates, to permit the earth bonding of all cable
glands. The minimum size for main earth bars shall be 70mm2 copper. For switchboards
protected by ACB, the main earth bar and tee-off connection shall not be smaller than
300mm2 and 150mm2 copper respectively. The Contractor shall give the Engineer not less
than 28 days notice of despatch of cubicle switchboard from the manufacturer’s work.
The various cubicles housing the respective switch/control units shall be so arranged as to
give a multi-tier arrangement and shall included a cabling and wiring chamber of ample
dimensions with provision for terminating armoured cables, where applicable. All
secondary wiring shall be PVC insulated and not less than 1.5mm2 stranded single core.
Each connection for the secondary wiring shall terminate at an approved type of terminal
block with a coded ferrule.
Connectors or soldered joints shall not be permitted in the secondary wiring which shall,
wherever possible, be grouped and laced together in a neat manner.
2/6
Section – Two
Electrical Specification
Part – 2
General Electrical Specification
The installation of cable passing through busbars chambers to interconnect items of
switchgear or distribution equipment will not be permitted. Insulators, including busbar
supports, shall be non-hygroscopic and non-deteriorating. The use of fibrous materials,
linseed oil, varnish, etc. is not acceptable.
b)
Fuse-Switch Units and On-Load Switches
1.
The units shall be of air-break insulated, metal-clad type and be designed to ensure safety to
operating personnel. The fixed contacts shall be provided so that maintenance of the unit
can be carried out in safety with the busbars live.
2.
All switches shall give visible ON/OFF position indicators and shall be lockable in both
these positions.
3.
The units shall preferably comprise fuse-switches having integral fuses in which the air
break switch and connections from it to the associated fuse shall be designed to minimise the
possibility of a phase-to-phase short circuit. In either case the switch shall be capable of
breaking 3 times the normal rated current at 0.3 power factor and 110% rated voltage and
making and carrying the system prospective symmetrical fault-power, but limited in
magnitude and duration by the cut-off characteristic of the largest HRC fuse link that may be
fitted to that unit.
4.
The rated normal current of the fuse-switch unit shall be as stated in the schedules forming
part of this specification or to suit the load stated therein. Interlocks shall be provided to
ensure that the unit access door can only be opened when the associated switch is open and
the switch cannot be closed until the access door is closed.
c)
High Rupturing Capacity (HRC) Fuses
1.
Fuses of the HRC type shall be provided and be such that the fuse carrier is easily withdrawable for replacement of the fuse. All fuses shall be fitted with a visual device to indicate that
the fuse has operated.
2.
Time/Current characteristics of all fuse links shall be provided when requested by the
Engineer.
3.
The current rating of fuse links shall be of sufficient capacity to afford short-circuit
protection for the loads as stated in the schedules forming part of the Specification whilst
remaining inoperative for such transient currents that may occur in the circuit. The rating
where applicable, shall be such that the characteristic of the fuse link matches the
characteristic of any contactor thermal device in the circuit.
d)
Air Circuit Breakers
1.
Circuit breakers shall be draw-out type with electronic trip units as specified on the
associated drawings. Circuit breakers shall have interrupting, close and latch, and 30-cycle
withstand ratings that meet the application requirements. Interrupting rating shall be
available up to 130 kA RMS amperes without fuses. Close and latch ratings to 65 kA
available on all frame sizes. Thirty-cycle withstand rating available up to 100 kA to provide
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Section – Two
Electrical Specification
Part – 2
General Electrical Specification
maximum coordination with downstream circuit breakers. Circuit breakers shall be available
in 3200 A frame sizes. An adjustable rating plug (range of 0.4-1 times the sensor plug value)
and a field-replaceable sensor plug (available in standard amperage steps from 50% to 100%
of the frame size) shall determine the ampere rating of the circuit breaker. The enclosure
2.
Circuit Breakers:
a)
b)
c)
d)
e)
f)
g)
h)
i)
j)
k)
Circuit breaker shall be draw-out type electrically operated.
The case of the circuit breaker shall be a polyester thermoset material providing
high dielectric strength.
All circuit breaker operating mechanisms are to be two-step, fully- stored energy
devices for quick-make, quick-break operation with a maximum of a five-cycle
closing time. Open-close-open (O-C-O) cycle shall be possible without
recharging. Motor operator shall automatically charge when circuit breaker is
closed. Actuation of the operating handle or an operation cycle of the circuit
breaker motor is to charge the closing springs (step one) and operation of a local
"close" button is to close the circuit breaker contact (step two). Closing the circuit
breaker contacts shall automatically charge the opening springs.
Current-carrying components shall be completely isolated from the accessory
mounting area and double insulated from the operator with accessory cover in
place.
Each phase inside the circuit breaker shall be completely isolated from other
phases and ground by polyester thermoset material.
Padlocking provisions shall be furnished to receive up to three padlocks when
circuit breaker is in the disconnected position, positively preventing unauthorized
closing of the circuit breaker contacts.
Provisions for up to two key locks shall be furnished allowing locking in the
disconnected position. Provisions for locking in the connected, test and
disconnected positions by padlock or key lock shall be available as a option.
Located on the face of the circuit breaker shall be buttons, with optional lockable
clear cover, to open and close the circuit breaker and indicators to show the
position of the circuit breaker contacts, status of the closing springs, and circuit
breaker position in the cell. An indicator shall show "charged-not OK to close" if
closing springs are charged but circuit breaker is not ready to close. Circuit
breaker racking system must have positive stops at the connected, test,
disconnected and withdrawn positions.
Circuit breaker must be equipped with an interlock to discharge the stored energy
spring before the circuit breaker can be withdrawn from its cell. Circuit breaker
must provide a positive ground contact check between the circuit breaker and cell
when the accessory cover is removed while the circuit breaker is in the connected,
test or disconnected positions.
Primary connectors that can be rotated to provide flexible vertical or horizontal
connections shall be available as an option. Front connections shall also be
available for shallow depth equipment designs.
Ready-to-close contact must be available to indicate remotely that the circuit
breaker is "ready to close." The circuit breaker is ready to close when it is open,
spring mechanism is charged, a maintained closing order is not present, a
maintained opening order is not present, and the circuit breaker is in an
operational position.
2/8
Section – Two
Electrical Specification
l)
m)
n)
o)
3.
Part – 2
General Electrical Specification
Secondary wiring shall be front accessible and available in cage clamp or ring
terminal connections. Secondary wiring must not be accessible when switchgear
door is closed.
Circuit breaker shall provide long service life. The 3200 A circuit breaker frame
and those of lower ratings must be certified to perform a minimum of 10,000
operations without maintenance. The 4000 A and 5000 A frames must be certified
to 5,000 operations without maintenance.
Circuit breaker shall be equipped with a visual contact wear indicator.
Low-voltage power circuit breaker arc chutes containing asbestos will NOT be
accepted.
Trip System:
a)
b)
c)
d)
e)
f)
g)
h)
i)
j)
k)
l)
m)
n)
Circuit breaker trip system shall be a electronic trip unit.
Electronic trip unit shall be UL Listed as field-replaceable and upgradeable without
special adjustments to the mechanism.
Electronic trip unit is to be true RMS current sensing
Trip unit functions shall consist of adjustable long-time pickup and delay, optional
short-time pickup and delay, instantaneous, optional neutral protection and optional
ground-fault pickup and delay.
Adjustable long-time pickup (Ir) and delay shall be available in an adjustable rating
plug that is UL Listed as field-replaceable. Adjustable rating plug shall allow for
nine long-time pickup settings from 0.4-1 times the sensor plug (In). Other
adjustable rating plugs shall be available for more precise settings to match the
application. Long-time delay settings shall be in nine bands from 0.5-24 seconds at
six times Ir.
Short-time pickup shall allow for nine settings from 1.5-10 times Ir. Short-time
delay shall be in nine bands from 0.1-0.4 I2t ON and 0-0.4 I2t OFF.
Instantaneous settings on the trip units with LSI protection shall be available in nine
bands from 2-15 times In. Instantaneous setting shall also have an OFF setting.
All trip units shall have the capability for the adjustments to be set and read locally
by rotating a switch. Optional trip units shall have the capability to electronically
adjust the settings to fine increments below the switch settings. Fine increments for
pickup adjustments are to be one ampere. Fine increments for delay adjustments are
to be one second.
Ground-fault protection shall be available for solidly grounded three-phase, threewire or three-phase, four-wire systems. Trip unit shall be capable of the following
types of ground-fault protection: residual, source ground return, and modified
differential. Ground-fault sensing systems may be changed in the field.
Ground-fault settings for circuit breaker sensor sizes 1200 A or below shall be in
nine bands from 0.2-1.0 times In. The ground-fault settings for circuit breakers
above 1200 A shall be nine bands from 500 to 1200 A.
Neutral current transformers shall be available for four-wire systems.
Trip unit shall provide local trip indication and capability to indicate local and
remote reason for trip, e.g., overload, short circuit or ground fault.
Trip units shall be capable of communicating on MODBUS® networks.
Trip units shall be available to provide additional protection by offering adjustable
inverse definite minimum time lag (IDMTL). IDMTL provides optimized
coordination by the adjustment of the slope of the long-time delay protection.
2/9
Section – Two
Electrical Specification
o)
Part – 2
General Electrical Specification
Trip units shall be available to provide real time metering. Metering functions
include current, voltage, power and frequency.
e)
Moulded Case and Miniature Circuit-Breakers
1.
Circuit-breakers shall be moulded case all insulated pattern with silver tungsten contacts and
quick make break trip-free mechanism.
It shall be mounted in sheet steel boxes of approved design and where several breakers are
grouped together they shall be housed in metal enclosures similar in design to cubicle
switchboards.
Wherever miniature circuit-breakers provide final circuit protection they shall be grouped in
metal enclosed distribution boards.
Miniature circuit-breakers shall be hydraulic magnetic or thermal magnetic type and each
circuit-breaker shall carry its full rated current continuously, without tripping out, in the
enclosure specified. The calibration of the magnetic-hydraulic trip mechanism shall not be
affected by ambient temperature variations.
2.
Three-pole type circuit-breakers shall be so designed that the operation of the protective
device in any one phase shall cause opening of all three phases. All three loads shall be
controlled by three-pole type circuit-breakers. Circuit-breakers shall have thermal-magnetic
overload short-circuit protection. The characteristics of the protective devices and the
associated HRC fuse feeding the circuit-breaker distribution board shall be such that for all
current in excess of the maximum capability of the circuit-breaker, a time not less than 0.01
seconds shall exist between the maximum fusing time of the HRC fuses and the minimum
time of operation of the circuit-breakers at that particular value of current. They shall
confirm to BS 3871 Part2, with a short circuit rating as appropriate to the point of
installation.
f)
Distribution Boards
1.
General lighting and power distribution boards shall be 600 volts grade metal-clad pattern
pre-treatment galvanized sheet steel rigid welded construction and shall be supplied
complete with panel door, phase barriers, masking plates, earth terminal bar, miniature
circuit-breakers or cartridge fuses and circuits charts. All distribution boards shall be
manufactured under license.
2.
Distribution boards intended to be installed in plant areas shall be of weatherproof industrial
type construction, and those intended to be installed in office and residential areas shall be
appearance suitable for installation these type of buildings. Both types shall be provided
with top and bottom removable metal gland plates which shall be drilled to suit cable glands
or conduit entry. Spare holes shall be provided, two each at top and bottom, and fitted with
32mm stopping plugs and lock nuts.
3.
Each distribution board shall be clearly labelled indicating its service and all 3-phase
distribution boards shall be fitted with white labels red engraved DANGER-and the
appropriate 3-phase voltage. Circuit charts shall indicate phasing, connected load and circuit
2/10
Section – Two
Electrical Specification
Part – 2
General Electrical Specification
breaker or fuse rating. Single phase boards shall include phase color identification discs.
4.
One earth terminal shall be provided for each earth cable terminated. Each distribution board
shall be fitted with phase barriers of an oil and fire resisting insulating material whereby it is
not readily possible for personnel to touch the phase busbars. Insulating barriers shall be
fitted around the circuit breakers such that only the front surface and toggle of the circuit
breakers are showing. Each distribution boards shall be fitted with a card index of circuits
contained in a suitable plastic pocket secured on the inside of the door panel.
5.
Distribution boards shall be fitted with an integral incoming on-load switch. All distribution
boards shall be fitted with a neutral busbar having facilities for terminating as many neutral
cables as single-phase ways in the board. Neural bar terminations shall reflect the circuits
served, circuit No.1 in Terminal No. 1, Each distribution board shall be fitted with an earth
stud located in an accessible position. All metal parts of the board except carrying parts shall
be bonded together electrically and to the earth busbar.
6.
Panel boards of the types scheduled shall be in line as indicated on drawings.
g)
Contactors
1.
Contactors shall be of the air-break type fitted with arc shields and be mechanically latched
or electrically held in. All essential process drives for safe running or shutdown of the
service will be controlled by contactors of the mechanically latched type. Only non-essential
drives will utilise electrically held in contactors.
The closing coil of mechanical latched contactors shall be suitable for operation from the
D.C power supply specified but shall operate satisfactory, with a coil temperature of 50C,
over a voltage range of 80-120% of nominal voltage.
The operating coil for electrically held in contactors shall be suitable for operation on the
nominal single phase A.C supply but must be capable of satisfactory operating if the voltage
is 80% of its nominal value. Electrically held in contactors shall hold in at a voltage of 76%
of their nominal value.
2.
Unless otherwise specified, operating coils shall be suitable for single phase A.C supply an
switching facilities but fitted with rectified D.C coil and separate fuse for the control circuit.
3.
The shunt trip release coil of mechanically latched contactors shall be suitable for operation
from the D.C power supply specified but shall operate satisfactorily, with a coil temperature
of 50C over a voltage range of 80-120% of nominal voltage.
But contacts of the rolling self-cleaning type shall preferably be utilised and all portions
likely to suffer from arcing shall be easily removable. If rocker type contactors are used,
they shall be fitted with electro-magnetic arc control devices.
The nominal current rating of a contactor for direct start motor drives shall not be less than
120% of the nominal full load current of the motor. Minimum current rating of contactors
shall be 30 amps.
2/11
Section – Two
Electrical Specification
Part – 2
General Electrical Specification
h)
Main and Sub-main Control Equipment
(Low Tension switchboards-motor control centres.)
1.
The Contractor shall supply the motor control centers and suitable for mounting indoors and
with IP55 protection and shall be designed for an ambient temperature of 50C unless
otherwise stated. The motor control centers (MCCs) shall be in the form of floor-mounted,
robust, rust-proof sheet steel cubicles, Form-4 construction dust and damp proof protected
unless otherwise stated any where else in Specification.
2.
Each cubicle shall be clearly marked with labels. The MCCs and distribution boards shall be
subdivided into sections being fully screened (separated) from its neighbour. Provision
shall be made for front access both for installation and maintenance unless otherwise stated
and for cable installation with the board live.
Incoming and outcoming cables shall be top or bottom entry. All motor starters shall be of
the ‘direct-on-line’ type up to 5KW and star delta star above unless otherwise stated in the
particular specification.
The busbars shall be mounted at the top of the MCCs. The busbars for the motor control
centre are to be for 3 phase and neutral and are to be 98% pure electrolytic copper of the
stated capacity. The fault level of the busbars, droppers and associated apparatus shall be
suitable for 50kA for 1 second unless otherwise specified.
The busbars shall not be graded and shall be capable of future extension at either end.
Where busbars are accessible, they shall be insulated to prevent accidental contact. The
busbar systems offered shall carry A.S.T.A certification.
3.
All control circuits shall be 220V AC.
4.
Unless otherwise specified the motor starter units shall be arranged in multi-tier
assemblies. All starters shall be readily accessible for maintenance and replacements of
parts.
5.
The Contractor shall supply drawings and diagrams.
6.
Each Starter shall comprise, as a minimum :
a)
Each starter shall be fitted with transformer operated lamps indicating :Motor running (green)
Motor stopped (red)
Overload tripped (amber)
b)
Each starter shall be fitted with one set of local start/stop push buttons and a
local/remote, or local/remote/auto selector switch, if required.
c)
Each starter to be equipped with labels giving drive designation, plant number and
control operation.
2/12
Section – Two
Electrical Specification
7.
Part – 2
General Electrical Specification
d)
Provision for padlocking the isolator in the ‘OFF’ position.
e)
One control circuit MCB fuse and one copper link.
f)
External mechanical hand reset to be provided.
g)
All instruments shall have compatible appearance size and finish.
h)
Ammeters and voltmeters shall be provided on incoming feeder and shall be flush
mounted.
i)
All motor over 10KW shall be provided with ammeter and selector switch.
j)
On-load triple pole isolator with two normally open and one normally closed
auxiliary switches. The isolator to be mechanically interlocked with the starter
component door and capable of breaking the motor stall current and of making onto
a fault at the motor terminals.
k)
Moulded case circuit breaker.
l)
One triple pole thermal over-current relay incorporating over-current and single
phase protection with adjustable trip settings.
m)
Each starter control wiring terminal block shall include control terminals for
connection of remote pushbuttons, auto circuits and local to motor emergency stop
pushbuttons.
n)
Each starter to be equipped with labels giving drive designation, plant number and
control operation.
o)
All the auxiliary contacts to be wired down to the starter terminal block.
p)
Triple pole contactors to be fitted with three normally open and three normally
closed auxiliary contacts.
Isolators/Moulded case circuit breakers to be provided with facilities for padlocking in the
‘OFF’ position.
All cubicles forming an MCC shall be bonded together with a copper earth tape extended to
the length of the MCC. This earth tape shall be 30mm x 6mm minimum and provision shall
be made for connection to the building earthing system.
i)
Motor Starter Control Circuits
1.
Unless otherwise stated all the alarms and trips indicated, including overload trips,
shall flash on initiation and sound a klaxon. Pressing the ‘ACCEPT’ button shall
mute the klaxon and reduce the flashing lamp to a steady illumination. After alarm
sources has cleared, pressing a ‘RESET’ button shall extinguish the lamp. If
several alarms occur nearly simultaneously, the first shall flash and all other be at
steady illumination. Any alarm occurring after a prior one has been accepted shall
cause the new alarm to flash and the klaxon to sound.
2.
A anti pumping circuit shall be provided in every instance of automatic control by a
“2-wire” system, to ensure that in the event of tripping any drive while in automatic,
the drive shall remain tripped until manually re-primed. This shall not apply to 3wire control (fleeting contact). Where a priming circuit is employed a lamp shall be
2/13
Section – Two
Electrical Specification
Part – 2
General Electrical Specification
mounted on the starter door, to indicate “starter primed”.
3.
Prior to delivery of the MCC a full simulation test of the logic system shall be
carried out at Works, witnessed by the Engineer. By the use of suitable simulated
inputs and outputs, the function of the logic provided shall be included.
4.
A ‘TEST’ button shall be provided to test all alarm and indication lamps on the MCC. With
the exception of the overload trip lamps which shall be mounted on the starter cubicle, all
other alarm lamps shall be grouped in one common location.
1.10
SWITCHES/ ISOLATORS
a
Provide fusible and non-fusible switches of one manufacture Type `HD' with quick-make,
quick-break contacts, horsepower-rated where required, to match the motor protected.
Provide holders to accept specified fuses. Switches to include mechanical cover interlocks
and line side barriers.
b
Where applicable and available, switches shall be "Approved For High Service Factor".
c
Provide safety disconnect switches adjacent to motors and other equipment. Use switches
of one manufacture throughout.
1.11
TRANSFORMERS
a
The transformer shall be Oil cooled/Dry-type transformer cast resin encapsulated and shall
comply with Local Electricity Authority (DEWA) requirements. Priority shall be given to
take the transformers from (DEWA).
b
The transformer shall be 3-phase, outdoor/indoor, two winding, solvent less cast epoxy
resin, vacuum pressure impregnated windings, with minimum class F insulation on inner
LV cores and class B on outer MV cores, rated for continuous operation under worst site
ambient conditions at full load, and comply with IEC 726. Temperature rise is not to exceed
70 deg. C over the ambient temperature for class B insulation and 90 deg. C over the
ambient temperature for class F insulation. The core shall be constructed from laminations
of cold rolled, grain oriented sheet steel. All parts of the core shall be of the robust design
capable of withstanding any shocks to which they may be subjected during lifting,
transportation, installation and services.
The high and low voltage windings shall be wound with aluminium or copper conductor
material and encapsulated in glass fiber or quartz reinforced epoxy resign. The HV windings
shall be interconnected by interconnection pieces with similar insulation or by other
approved method.
Insulation and Encapsulation to be humidity resistant, explosion and fire resistant, self
extinguishing, giving non toxic gases in the event of fire.
The transformer shall be housed in an enclosure made up of sheet steel or other approved
metal as per DEWA regulations. The minimum degree of protection to be provided shall be
IP-21/IP-65.Access shall be provided in the enclosure for the selection links.
2/14
Section – Two
Electrical Specification
Part – 2
General Electrical Specification
Tapping is to be provided on the MV side by means of re-connectable links (off circuit),
giving +/- tapping on the transformer.
Rubber sound isolation pads are to be provided between core and coil assemblies and
between base and housing. Temperature Monitoring shall be provided by externally
mounted tripping units giving alarm and trip at two stages with about 20 deg. C temperature
difference, actuated by three
embedded thermistor sensors in LV windings. Additional thermal monitoring to be provided for
cooling fan operation. Contacts shall be provided for remote alarm.
c.
The transformers shall comply with IEC 76,137,354,606 and 726 and BS 2562 and 6121.
HV terminations shall comprise of three pole air insulated cable box. The connections from HV
windings to the HV cable box shall be flexible in compliance of Class 6, table 4 of IEC 228.
LV terminations shall comprise of four pole air insulated cable box with detachable gland
plate, complete with brass and double compression glands for receiving and terminating 8 no of
single core 630 sq. mm ELPE/PVC cable.
The LV neutral shall be brought out through a separate bushing with in the cable box and shall
comprise of a detachable neutral to earth link with a separate earthing terminal.
d.
The transformer shall have the following characteristics:
Rated Power
:
As marked on the drawings
Frequency
:
50Hz
Rated Voltage Primary : 11kV
Secondary : 0.4kV
Winding Connections : Dyn11, Neutral insulated and brought out.
Impedance at rated current : 5%
Rated power frequency
withstand voltage
: 28kV
Lightning impulse
withstand voltage
: 75kV
Short circuit apparent
power of the system at
location
: 500 MVA
Shot circuit withstand
duration
: 1 second
Terminal connections
MV side : cable sealing ends bolted from above
LV side : Cable glands and fittings bolted from above
e.
The following accessories shall be included:
Fault making type Earthing switch on MV side of the housing interlocked with door and visible from
outside the enclosure with trip contact for tripping MV protective device before closing earthing
switch.Cable lugs for LV and MV terminations etc.
f.
Type test and Routine test Certificates to be provided. Type test certificates in general shall include
2/15
Section – Two
Electrical Specification
Part – 2
General Electrical Specification
lightning impulse withstand, temperature rise, short time current withstand and enclosure protection
in compliance with IEC 529. Routine test shall include measurement of noise level, winding
resistance, voltage ratio, polarity/vector group, impedance voltage , load losses, no load losses, no
load current, induced voltage withstand test, and separate source voltage withstand test.
1.12
CAPACITOR BANKS
a.
The contractor shall provide, install, connect, test and commission an automatic power factor
correction capacitor bank in steps of 15KVAR or as shown on the drawings in order to maintain the
over all power factor at not less than 0.9 (lagging) at all times on the distribution associated with the
chillers and as shown in the drawing.
b.
The power factor improvement unit shall be automatic and generally comprise of the following :
Dry type capacitors with low power loss.
The capacitor bank shall not form part of the distribution board.
The switching of capacitors shall be controlled by a solid state reactor relay operating through
contactors.
The control unit shall include :
o
Auto/manual mode selector switch.
o
On/Off push button for each switching stage.
1.13 EARTHING AND LIGHTNING PROTECTION
a.
The Contractor shall connect each separate portion of the works to the main earth system. The main
earth system will be connected to the main intake switchgear for the installation, and/or earth
electrodes. Main earth bus bars will be in the form of 50mm x 6mm HDHC bar copper strip. Unless
otherwise specified, the frames of all individual electrical apparatus shall be solidly earthed by a
copper connection of not less than 90 sq. mm to the main earth bus bar or subsidiary earthing
connections running from the main earth bus bar to a particular group of equipment.
b.
All joints between flat copper strip shall be lapped and brazed. All stranded copper conductors shall
be terminated by crimped lugs of approved pattern-no straight through joints will be permitted;
crimped lugs shall be joined to secondary earth bars by steel bolts. At points of contact where bolted
connections are made, the copper surfaces shall be tinned.
The main earth bus bar and all subsidiary earth strips shall be fixed to concrete, brickwork and
steelwork by two-hole brass clamps at 1 meter centers. Details of cleat, rack and clip arrangements
shall be submitted to the Engineer for approval.
c.
The frames of switchgear equipment and tanks of transformers shall be earthed by a copper
connection of at least 90 sq. mm direct to the main earth bus bar on the main intake switchgear.
Unless otherwise specified, where cables having metallic sheaths or armouring terminate on a piece
2/16
Section – Two
Electrical Specification
Part – 2
General Electrical Specification
of plant, the sheath and armouring shall be bonded by copper connections to each other and to the
apparatus and items of plant. Separate earth Statutory Authority requirements shall be installed with
all armoured cables and shall be bonded to the earthing glands.
d.
All conduits and trunking shall have good contact between each section. Trunking shall have copper
bonding straps between each section.
Earth connections shall be made onto conduits by means of heavy type copper clamps.
Where flexible metallic tubing is used for the final connections to machines or other items of
equipment, separate conductor shall be installed between the rigid conduit system and the earth
terminal(s)of the equipment.
e.
All the cables conduits and trunking shall be adequately bonded to provide earth continuity.
Where joints are made in cables having metallic sheath or armouring, these joints shall be adequately
strong and well bonded to provide continuity and to keep continuity resistance down to the required
values. It shall be the Contractor responsibility to thoroughly test these joints.
f.
Continuity test and earthing test shall be undertaken to the satisfaction of the Engineer when the
installation has been completed.
g.
Earth rods shall consist of hard drawn copper (or copper bond where approved) rods, minimum
length 1.2m, having a diameter of not less than 17.5mm and having internal screw joints.
Earth rod covers shall be formed in concrete.
h.
Where a main earth is specified this shall consist of a number of hard drawn copper earth rods driven
into the ground.
Earth rods shall be connected to each other and to the main earth test point using triangular clamps
fixed to the head of each rod and earth tape. The earth tape must be buried 750mm below ground
level and rise vertically alongside each rod to enter the clamp.
Each earth rod shall have a concrete cover over it, set in flush with final ground level unless the earth
rod is installed through the bottom of a cable manhole or drawn in pit, in which case the cover shall
be permanently marked “Main Electrical Earth”.
i.
Where armoured cables and bus-bar trunking systems are installed then irrespective if the size or
resistance of the metallic armouring or casing, each armoured cable and bus-duct shall be provided
with an Earth continuity conductor, the cross sectional area of which must be grater than half that of
the conductor cross-sectional area provided that the resulting earth continuity conductor is not less
than required by local Electrical authority.
j.
The main earth shall have an earth resistance not exceeding one ohm.
k.
For lightning protection PVC coated copper tape mat shall be provided on the roof as shown on the
drawings complete in all the respect and to comply with the applicable local regulations.
2/17
Section – Two
Electrical Specification
Part – 2
General Electrical Specification
The mat shall be made with 25 x 3 mm pvc coated copper tape. Building steel structure, if approved
by the engineer, may be used as the down conductor. All the metalic Equipments installed on the
roof shall be bonded to the lightning protection tape. Any fittings to be used shall be factory made
only.
1.14
VIDEO INTERCOM SYSTEM
The contractor shall supply, install, test and commission a color video Intercom System for the
Apartments as shown on the drawings. All stations to be interlinked with each other so that it shall be
possible to call any flat from any of the station.
a.
Power Supply
1.
Control unit for video inter com system shall use co-axial cable. This unit together with
power transformer feeds all circuits, selects the calls, Guarantees the Audio/Video privacy
Tone…users. It incorporates a timer for the shooting and speech time with auto doubling in
case of answer of the call.
1.15
UNDER FLOOR TRUNKING SYSTEM (APPLICABLE TO THE EXTENT SHOWN IN
THE DRAWING)
1.
The contractor shall allow for supply, installation testing and commissioning of Under floor
Trunking system to be used for small power, Telephone and Data System.
2.
The layout of the under floor trunking as shown on the drawings is indicative only. The contractor to
make the shop drawing in co-ordination with the furniture layout and take the approval of the
Engineer prior to commencement of the work and or ordering the material.
3.
The under floor trunking shall be installed below the false flooring as shown on the drawings and as
required.
4.
Contractor to prepare a method statement for the installation of these under floor trunkings and take
approval from the engineer prior to commencement of the installation.
5.
the under floor trunking shall consist of three compartments out of which one shall be used for small
power wiring, second compartment shall be used for Telephone system and the third shall be used
for data system. Where ever no trunking has been shown, the floor boxes are to be connected through
suitable sized conduits.
6.
The system shall facilitate full compliance with latest IEE regulations and service outlet accessory
plate should be able to cater for BS, American and CEE-7 socket outlet as well as telecommunication
and
data sockets.
7.
Trunking lids and accessories shall be manufactured with 1.6mm sheet steel, body galvanised and
2/18
Section – Two
Electrical Specification
Part – 2
General Electrical Specification
cover to be treated with paint to match the wall finishes.
8.
The trunking shall be manufactured in standard length as adopted by the manufacturer and shll be
complete with earth terminals at both ends. Copper bonding links shall be used to connect the
earthing of the next length of the trunking.
9.
Over all dimension of the trunking shall approximately be 225 X 25 X 1.6mm.
10.
Purpose made service boxes and junction boxes to be provided from the same manufacturer. Each
service box should accommodate 2 nos. of 13A Switched socket outlet, one number Telephone outlet
and one number data outlet or as marked on the drawings.
11.
The box shall have a lift off arrangement so that the recessed tray lid can be closed when the box is
in use with cable protrouding safely. It shall be possible to shift the outlet service box to any desired
place along with the trunking route.
1.16
EQUIPMENT LOCATIONS
1.
Approximate locations of electrical equipment, fixtures switches, outlets, and the like, are given on
the drawings. Refer to the architectural drawings and room elevations for application. In absence of
definite detail exact location of outlets shall be determined on site as work progresses. Local
switches for lighting shall generally be installed on the lock side of doors. Verify switch locations
on the site.
2.
Device plates shall cover opening left for outlet box, and plates shall be attached to boxes in an
approved manner. Outlets and fixtures are to be located symmetrically, (i.e. centered in wall panels,
ceiling panels or tiles, columns, between and above doors and the like).
3.
The right is reserved to alter the location of equipment and outlets a distance of up to 3 metres
without involving a change to the Contract amount, providing notice is given prior to installation.
1.17
HOLES & DRILLING
1.
Pneumatic hammers and percussion drills are prohibited.
2.
Where not sleeved, make holes through concrete walls and floors by core-drill only. Obtain
Engineer’s approval before drilling.
3.
Seal holes and sleeves through floors to serve as water dam.
4.
Seal ends of conduits with conduit sealing bushings to provide hydrostatic seal against water within
conduit entering the building.
1.18
CUTTING AND PATCHING
1.
Lay out and install work in advance of other Sections for all new work. Bear all costs resulting from
failing to comply with this requirement.
2/19
Section – Two
Electrical Specification
Part – 2
General Electrical Specification
1.19
EXCAVATION AND BACKFILL
1.
Provide necessary excavating and backfilling inside and outside building required for work of this
Division, performed as specified under another Division of the work, except as modified below.
2.
Keep excavations free from water, pump as necessary. Provide and maintain adequate heat, shoring,
other necessary temporary protection.
3.
Excavation for underground services shall be to required depths and dimension and shall be prepared
as required, so that no portion of any conduit or duct bank, bears directly against any rock or other
hard surface.
4.
Remove and dispose of all surplus excavated material.
5.
Backfill promptly after approval of work. Prevent damage to or displacement of walls, piping,
conduits, waterproofing and other work.
6.
For direct buried conduit and cable in all soiled conditions excavate to 150 mm (6") below and a
minimum of 200 mm(8") to either side of the cable run. Fill back with a bedding of sand.
7.
Provide sleeves under all roads and paved areas.
8.
Before backfilling, obtain approval. Remove all shoring during backfilling.
9.
Backfill trenches within building, with clean sharp sand in individual layers of maximum 150 mm
(6") thickness, compacted to a density of 100% Standard Proctor. Hand compact the first layers up
to a compacted level of minimum one foot. Hand or machine compact the balance up to grade, using
approved equipment.
10.
Backfill trenches outside buildings, not under roads, parking lots, or traffic areas, up to a compacted
level of 450 mm (18") above the duct bank with individual layers of material up to 150 mm (6")
thick, hand compacted to a density of 95% Standard Proctor, using sand or granular 'A' gravel.
Backfill the balance to 95% Standard Proctor, using approved equipment.
11.
Backfill all other trenches outside buildings with granular `A' gravel in layers not exceeding 150 mm
(6") thickness, compacted to 100% Standard Proctor density up to grade level; manual compaction
up to 450 mm (18") and mechanical compaction, using approved equipment, for the balance.
12.
Make good work where damaged by excavation and filling work of this Division. Repair any
subsequent settlement of fill placed under this Division and pay all costs in replacement of other
work damaged by such settlement and restoration.
1.20
CONCRETE WORK
1.
Provide concrete work where required for work of this trade in accordance with applicable
requirements specified in Concrete Division.
2/20
Section – Two
Electrical Specification
Part – 2
General Electrical Specification
1.21
HANGERS & INSERTS
1.
Provide necessary hangers and inserts for work of this Division.
2.
Fasten to cast-in place concrete by suitable drilled or cast-in inserts.
3.
Fasten to structural steel using bolts or welded fasteners.
4.
Do not use wood, chain , wire lashings, strap or grappler bar hangers except where noted or detailed.
5.
Support fixtures independently of ceiling suspension systems. Provide additional supports as
required, which shall be fastened to building structure steel members, joists, beams, etc., but not
metal pan or roof decking. Material for additional supports and their installation shall comply with
requirements of U.L.
6.
Support outlet and junction boxes independently of the conduits running to them where required by
electrical code and where deemed necessary by the Engineer’s use steel angle brackets or steel rods
to support outlets and fixtures, to the building structure.
7.
Drilled fastenings to concrete shall be self-drilling concrete anchors, Phillips 'Red-Head' or approved
equal. The maximum weight per fastening shall not exceed 25% of manufacturer's `pull-out' load
data.
1.22
PAINTING
1.
Hangers, support framing and all equipment fabricated from ferrous metals which are not protected
with zinc or other suitable corrosion-resistant finish shall have at least one coat of a
corrosion-resistant paint applied before shipment or immediately on arrival at the site.
2.
After installation, touch up all scratches, chips, other damage and defects in paint, using zinc
chromate primer or paint or special enamels as necessary to match the original.
3.
Finish and colour of all equipment shall be co-ordinated to provide uniform appearance.
4.
Painting of conduits and supports and other exposed surface work will be done under Painting
Section except as noted. Install materials in time to be painted together with mounting surfaces.
5.
Do not paint over nameplates.
6.
Refer to other Sections for special paint finished of equipment.
1.23
NAMEPLATES AND SCHEDULES
1.
Identify electrical equipment supplied under this Division with 3 mm thick black laminated plastic
nameplate to indicate equipment controlled to provide instruction or warning. Fasten each plate with
two chrome plated screws. Lettering shall be 6 mm high for small devices such as control stations
and at least 13 mm high for all other equipment. Submit a list of proposed nameplates for approval
before manufacture.
2/21
Section – Two
Electrical Specification
Part – 2
General Electrical Specification
2.
Provide panelboards with typewritten schedules identifying outlets and equipment controlled by each
branch circuit. Protect schedules with non-flammable clear plastic.
3.
Identify junction boxes, pull boxes, cover plates, conduits and the like, provided for future extension,
indicating their function (e.g. power, fire alarm, communication).
4.
Verify room names and names prior to listing on nameplates and schedules.
5.
Provide engraved laminated plastic nameplates for all emergency services. (EM) panelboards and all
associated disconnect switches and circuit breakers to read "Emergency Services, Do Not Interrupt".
1.24
BRANCH CIRCUIT WIRING AND FEEDER CABLES
1.
Provide all wiring, disconnects and outlets for connections to the elevators to the approval and
requirements of the elevator installer.
1.25
CONDUIT, RACEWAYS AND WIREWAYS
1.
Wire and cable shall be installed in conduit as follows:
Rigid galvanized steel conduit with threaded IPS fittings to be used:
1.
2.
3.
Where noted and required by regulations.
Where subject to mechanical damage.
For all exposed conduit work.
2.
Conduit embedded in concrete or buried below grade floors shall be approved rigid PVC type.
3.
Electrical metallic tubing (EMT) may be used in place of rigid conduit in dry locations subject to
governing regulations, embedded in masonry walls, and concealed above suspended ceilings.
Connectors shall be provided with factory-installed insulated throats. Connectors and couplings to be
forged steel.
4.
Fasten every conduit and cable to structure by means of approved conduit clamps or clips. Wire
lashing is not acceptable.
5.
Conceal conduits and wiring except where noted. Run exposed conduits parallel to building lines and
to other conduits. Provide every empty conduit with a pull rope (3 mm polypropylene rope) and
identify to designate its function (Power, Telephone, Fire Alarm and the like).
6.
Where conduit is installed in concrete slabs, obtain general approval, prior to commencing the work,
on both maximum dimension and cross-overs which may be used therein.
7.
Install conduits in such a manner as to conserve head room and interfere as little as possible with free
use of space through which they pass. Obtain approval for routing of same. Keep conduits at least
150 mm clear high temperature work.
8.
Conduit installed at the roof level of exposed structures, shall be run tight to roof deck, above purlins
and beams.
2/22
Section – Two
Electrical Specification
Part – 2
General Electrical Specification
9.
Run conduit exposed in mechanical equipment rooms, electrical rooms, fan rooms, and the like, and
installed after mechanical and other equipment is completed. Install fixtures, outlets, starters, etc., to
clear and to suit application.
1.26
WIRE AND CABLE
1.
Wiring to heating equipment shall be rated 90oC minimum, the ampacity of which shall be limited to
75oC value.
2.
Conductors used for all auxiliary systems (e.g. Fire Alarm) shall be tagged and/or colour-coded, and
where applicable shall agree with manufacturer`s wiring diagrams.
3.
Minimum wire size for power wiring shall be 4 mm unless specified otherwise. Control
wiring shall be 1.5mm red insulation. Maximum voltage drop between furthest outlet of any circuit,
when fully energized, and panel to which it is connected shall not exceed two percent except for
electric heating circuits which shall not exceed one percent.
4.
Cables shall be terminated with moisture-proof connectors, clamped to sheet metal enclosure by a
single non-ferrous locknut and grounding bushing.
5.
Number of wires indicated for lighting and power, motor and motor control, alarm, signal,
communications, and auxiliary systems is intended to show general scheme only. The required
number and types of wires shall be installed in accordance with equipment manufacturer's diagrams
and requirements, and with requirements of the installation, except that specification standards shall
not be reduced.
6.
Use compression joints and terminals for all control wiring; and all conductors 1.5mm and larger.
Mechanical connections are acceptable at panelboards and circuit breakers where these are part of
factory-assembly.
7.
Wire or cables in feeders, sub-feeders and branch circuits shall be colour-coded in accordance with
DEWA Code. Each end of feeder terminations (e.g. in Switchboard, Panelboards, switches,
splitters and the like) Code Phase A - Red, Phase B - Yellow, Phase C - Blue, Neutral - Gray.
8.
Include in each conduit, tubing and raceway, a code gauge green supplementary ground conductor
which shall be connected to suitable ground bus in equipment.
9.
The use of exposed plastic-jacketted cables shall be subject to approval of DEWA, but shall not be
installed in ceiling spaces used as return air plenums for mechanical air-handling systems.
10.
Cable Installation
1.
General
1.
2.
The arrangement of cables and all methods of installation shall be approved by the
Engineer.
Cables shall be installed from terminal point to terminal point and straight-through
joints shall not be made unless approved.
2/23
Section – Two
Electrical Specification
3.
4.
2.
2.
2.
3.
Where cables pass under roads or rail tracks and where shown as being in ducts in
the particular specification, the cables shall be drawn into ducts.
The removal of temporary plugs, rodding and cleaning of the ducts shall be
responsibility of the Contractor.
Particular attention shall be given to the sealing of ducts where any of such ducts
enter cable trenches within the confines of the building.
Cables Direct In Ducts (Cont’d)
4.
4.
All cables shall be laid at depths specified or, where unspecified, at not less than
600mm for LV cables and 800 for H.V cables at all points and where this depth is
not possible approved mechanical protection shall be provided.
All underground cable routes shall be marked at 15 meter intervals, at changes of
direction and at straight through cable joints by approved markers.
Cables Direct In Ducts
1.
3.
The radius of each bend or change in direction of the route of any cable shall not be
less than that laid down in the relevant table of manufacturer regulations and shall
generally not be less than eight times the overall diameter of the cable.
The spacings of cable supports shall be those laid down for the relevant size and
type of cable in the current issue of the local regulations, but the horizontal
longitudinal distance between wire armoured cable support centers shall not exceed
1 meter, the horizontal distance between support centers for either type of cable on
vertical runs is not to exceed 1 meter. Cables of and less than 50mm external
diameter shall be supported at not more than 800mm centers.
Cables Direct In Ground
1.
3.
Part – 2
General Electrical Specification
Where cables are detailed to be drawn into ducts, cable pulling grips with rotating
eyes shall be used and the cables shall be supported on rollers without sharp edges
during drawing operation. All cable ducts shall first be cleaned and proved by
drawing a mandrel of slightly less diameter than the duct immediately before pulling
the cables. Suitable man-holes shall be provided for pulling the cables in ducts.
Cable Laid On Trays
1.
2.
3.
Cables shall be laid in a single tier on the cable tray, unless otherwise approved and
neatly installed. Trays shall only be cut along a line of plain metal (not through
perforations). All cut edges shall be prepared and treated accordingly to original
finish of metal. Where welding have been employed, in fabrication and also on
galvanised tray, a zinc rich paint shall be used for this treatment.
Bends and tees shall be made of the same material, finish and thickness as straight
trays. At each end of the bends and tees, a minimum of 10mm straight run shall be
provided.
Cable trays shall be supported by mild steel galvanise brackets at regular intervals
of 1.2m maximum and at 225mm from bends and tees. Mushroom-headed steel
roofing bolts and nuts shall be used for the installation and coupling of trays.
Cable trays brackets shall be sufficient depth to provide access to the rear of the tray
2/24
Section – Two
Electrical Specification
4.
5.
2.
3.
4.
5.
All jointing material to be used shall confirm to the relevant BS and DEWA
requirements and the Contractor shall state the quality of the compounds he
proposes to use, which shall be entirely suitable for the site conditions.
All cables shall be colour coded in accordance with the IEE Regulations current
edition and amendments and all sealing and jointing work shall be in accordance
with the best current practice and of fist calls workmanship.
Joints in PVC or XLPE cables shall not be carried out without the written approval
of the Engineer. Low tension cable joints shall incorporate compression type
ferrules with polyethylene tape insulation housed in a plastic joint box and sealed
with cold pouring resin filling.
Where single core cables are used, all necessary precautions shall be taken to
prevent hysteresis. Ferrous plates through which the cables pass shall be slotted and
brass glands and sockets shall be used. Single core cables shall be very rigidly
clamped to prevent distortion under short circuit conditions.
The ends of each PVC/SWA/PVC cable shall be terminated in brass compression
type cable glands of the correct size which shall secure the cable inner sheath and
ensure effective electrical continuity between the cable armouring wires and the
metal enclosure on which the cable is terminated. A copper earth link shall be taken
from the cable termination point to an associated sub-switchboard or main
switchboard earth bar. XLPE cables shall be terminated in terminal boxes or other
equipment supplied under another Contract, the Contractor shall be responsible for
carrying out the terminations in accordance with the requirements specified above
including the supply and jointing of tails where necessary and the testing to verify
correct phasing of all cores.
Identification
1.
2.
1.27
for easy installation of PVC saddle type fixings.
All cables shall be secured to cable trays by means of PVC covered copper saddles
of the two screw fixing of type of PVC covered metal strip with non-corrodible
cheese-headed screws and nuts. The shanks of the screws shall be protruded beyond
the nut by more than three threads. Alternatively purpose made cable fixing devices
may be proposed for consideration. Horizontal and vertical clearance between
cables shall be such that no reduction in rating is necessary.
Cable Terminations
1.
6.
Part – 2
General Electrical Specification
All cable ends shall be marked to identify the cable connection. Identification lables
for all cables shall give the cable an approved reference number.
All cable shall have a label fixed to them below each cable joints, also where the
cables passes through ducts and trenches at each exit from or entry to such ducts and
trenches and where the cable enters a room or building. The label shall indicate the
cable potential and destination as well as the cable number.
OUTLET, JUNCTION AND PULL BOXES
1.
Use suitable electrical boxes for terminations and junctions on conduit work. Install pull
boxes where necessary to permit installation of conductors. Support pull boxes, outlet
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Section – Two
Electrical Specification
Part – 2
General Electrical Specification
boxes, panels and other cabinets independently of conduit.
2.
Provide each light switch, wall receptacle and other device with an outlet box of suitable
dimensions and a faceplate. Outlet boxes shall be adapted to their respective locations.
3.
Electrical boxes and panels shall be code-gauge sheet metal, galvanized or with suitable
protective treatment. Secure covers with screws or bolts.
4.
Outlet boxes shall not be installed "Back-to-Back" in walls; separate by a minimum of 150 mm.
5.
Use "Masonry Type" outlet boxes for flush installation in masonry walls.
6.
Install surface mounted devices, in cast conduit fittings, with threaded hubs and galvanized steel
faceplates.
7.
Main pull and junction boxes (excluding obvious outlet boxes) shall be clearly identified by painting
the outside of the cover in accordance with the following schedule:
- Lighting
Yellow
- Power
Blue
- Emergency Power
Orange
- Fire Alarms
Red
- Telephone
Cream
or as approved by Engineer.
8.
In addition, each box shall be identified with a system and service designator of logic reference to the
service.
1.28
PANELBOARDS
1.
Provide handle locking devices on circuits breakers feeding Plumbing, Heating, Ventilating
equipment and controls and all auxiliary systems, time switches, and other as noted. Paint handles
white, to permanently identify location and function. Provide 12 spare handle locking devices for
future use.
2.
Circuit numbers on drawings do not necessarily correspond to the numbers on the lighting panels.
Circuits sharing a common neutral shall not be connected to the same main. Panel circuit breakers
which are used directly for the switching of lighting fixtures shall be grouped in consecutive
numbers commencing at breaker number one.
3.
Provide empty conduits from flush panelboards, and others as noted, terminating in accessible
ceiling spaces, sized to accommodate spare and space breaker provisions. One 25 mm (1") conduit
for each three spare breakers or space.
1.29
ELECTRIC WORK FOR OTHER DIVISIONS
1.
Examine Architectural and Mechanical (Plumbing, Heating, Ventilating and Air Conditioning) plans
2/26
Section – Two
Electrical Specification
Part – 2
General Electrical Specification
and specifications to determine extent of electrical work in connection with these Divisions which is
to be done under the work of the Electrical Division.
2.
In general, all motor starters and associated controls for mechanical equipment will be supplied
under that Division of the work which supplies the equipment, for installation and connection under
the work of the Electrical Division 16. Refer to the Mechanical Division 15 Specifications,
drawings, and schedules for the exact intent and extent of the work to be included in the Electrical
Division.
3.
Co-ordinate the exact location and verify characteristics of electrical provisions for the work of the
Mechanical Division.
4.
The locations of starters, motors and associated equipment indicated on the drawings are
approximate and diagrammatic only. Co-ordinate with the work of the Division 15 Mechanical
Trade Sections to ensure proper location of equipment. The exact locations of conduit terminations
at Mechanical units shall be determined from equipment manufactures' approved shop drawings.
Conduits must be installed to enter only in the locations designated by equipment manufactures.
5.
Provide safety switches required for disconnection of remotely controlled motors, and where
required at motors by safety regulations whether shown on the drawings or not. Where required at
fan motors, they shall be concealed in the fan housing if possible.
6.
Provide for the 220 volt mechanical equipment where noted, all necessary wiring and connections
including wiring and installation of starters, thermostats, aquastats, speed controllers and time
switches controlling equipment.
7.
Where motor starters, switches and the like, are grouped together, a suitable 19 mm (3/4") thick
plywood panelboard shall be provided to which all such equipment shall be secured. Provide all
necessary angle iron supports for support of panel board and paint entire assembly with two coats of
enamel
8.
Provide weatherproof unfused safety disconnect switches, fastened to exterior of outdoor units, to
approval.
9.
Connect high temperature thermostats "Firestats" provided in ductwork by Division 15, to exhaust
fan systems, to provide fan shutdown on activation.
10.
Refer to Equipment Schedule on drawings for further Detail.
11.
Architectural Sections:
In addition to the work shown, perform the following:
1.
Provide all wiring and connections for Employer's Equipment, noted.
1.30
GROUNDING - GENERAL
1.
Ground all electrical systems in accordance with provisions of the Electrical Code.
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Section – Two
Electrical Specification
Part – 2
General Electrical Specification
2.
Install grounding conductors to permit the shortest and most direct path from equipment to ground.
Install grounding conductors in rigid galvanized conduit with both conductor and conduit bonded at
both ends. Provide bonding jumpers with approved clamps to maintain ground continuity of metallic
raceway systems at all expansion joints.
3.
Ground connections to grounding conductors shall be accessible for inspection and made with
approved solder less connectors bolted to the equipment of structure to be grounded. Clean contact
surface prior to making connections to ensure proper metal to metal contact. Connections shall be of
the type that grounds both conduit and conductor, and cap screws, bolts, nuts and washers shall be
silicon bronze.
1.31
WATERTIGHT SEAL AT EXTERIOR WALLS
1.
Provide "Link-Seal" sleeve devices distributed by Corrosion Services Limited, or approved equal,
cast into exterior walls below grade for conduits and cables which pass into finished spaces. Convert
non-metallic ducts to rigid steel conduits through such seals.
1.32
FIREPROOFING & SEALING
1.
Make watertight seal at sleeves at other openings through floors above grade. Sleeves to extend
minimum 25 mm (1 inch) above finished floors.
2.
Provide Fireproofing protection of openings through floors and fire rated walls.
3.
Roof flashing for conduit feeders to roof mounted equipment shall be sealed and flanged to roof with
Thaler or equal pre-insulated aluminium flashing sized to suit. Install in accordance with
manufacturer's instructions and details.
2/28