Download SECTION 16808

SECTION 16808
INSTRUMENT WIRING STANDARDS
808.01
GENERAL
The terms “or equivalent” in the following, means that
substitution of like styles or kinds are acceptable with the approval
of the specifying Engineer.
808.02
TERMINAL BLOCKS
Terminal blocks for Instrument signal
and power applications shall be 8 mm DIN Rail Mounting.
A.
Accesories , such as “End stops”, “End
plates”, “Offset brackets”, “Circuit separators “ etc. are to be
used as standard.
B.
C.
DIN Rail mounted 8 mm Fuse blocks, with
Blown Fuse
Indicator (BFI) shall be provided on all
+24Vdc supply legs.
D.
Fuse blocks, with BFI shall be provided
on the field return leg.
E.
Color of blocks to be gray.
F.
Terminal block screws, shall be of the
“sliding shoe” type, this is to avoid the possibility of the screw
cutting the wire at the tightening point(s).
808.03
TERMINAL BLOCK LAYOUT
A.
In general, terminal blocks will be stacked vertically.
B.
All field connection wiring (to
transmitters), shall be connected to the left side.
C.
All power supply connections (+24Vdc
and Com) will be connected to the right side, this includes
power supply jumpers.
D.
All other connection will be on the right
side.
E.
All loops will have the following vertical
blocks, from the top down:
1.
+24Vdc supply, which shall be bussed.
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2.
+24Vdc to field transmitter,
3.
Return from transmitter
(connected via a BFI) to Signal “home run” (the
positive side of the two wires going to the controller or
PLC I/O port),
4.
Common (connected to
the “home run” return), which shall be bussed to the 24Vdc power supply (aka common).
5.
Spares.
6.
Shield and the drain wires
from the field and “home run”. These shall be
connected to case ground only.
7.
At a minimum there shall
be six (6) terminal blocks per loop.
8.
“Circuit separators” shall
separate each loop.
808.04
WIRING
A.
All instrument field wiring shall be
Belden Industrial # 3076F - Instrumentation/Control Cable
DataBus(TM) ISA/SP-50 Fieldbus Cable Type A. Two 18
AWG, stranded, tinned copper conductors. Polyolefin
insulation. Overall shield of 100% Foil shield plus stranded,
tinned copper drain wire. Orange PVC Jacket, Data Rate:
31.25 Kbits/sec., Voltage Rating: 300V (or equivalent).
B.
Conductor jacket colors, for pairs, shall
be preferably black and white.
C.
In all cases the color black designates
the negative of DC voltage.
808.05
GROUND, SHIELDING, DRAIN WIRES
A.
Drain wires and the foil shields of both
the field and “home run” cables will be terminated ONLY
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ONCE and that is to the ground in the Field Power Supply
Cabinet.
B.
When there is an intermediate panel
before the final “read-out” device, the drain wires and shields
shall be connected but not grounded again.
C.
The purpose is to prevent the possibility
of current flowing, for any reason, along the length of the
shield/drain wire, such as towards to the readout device.
D.
The drain wire and/or shield shall be
insulated from becoming grounded at the ends by means of
a 2 inch insulating sleeve.
E.
Typically the unshielded portion of the
twisted pair shall be no less than 3/4” and no more than 2.0"
in length.
808.06
CABLE AND WIRE IDENTIFICATION
A.
A shrink wrap sleeve, “Ty-Wrap” style of
wire marker holder or other sleeve type of identification or
marker shall be fixed permanently to the over jacket of the
cable. Preprinted on this jacket marker shall be the
Instrument tag ID for the instrument or device that is being
serviced by the cable.
B.
For example, if the cable goes to
PCW006TIT-614, so mark the cable sleeve. If the cable
goes to PLC450 I/O port 27, so mark the cable sleeve.
C.
Cable tags shall be continuous from
end-point to end-point.
D.
For “Home run” cables the sleeve shall
be marked “Origin Building Number, Origin Junction Box
Number, Number of Pairs contained in cable, Destination
Junction Box Number, Sequence Number”.
E.
Sequence number shall be based on
Origin and Destination Junction Box numbers only, this
means where only two cables go between the same source
and destination, the sequence numbers shall be 1 and 2
respectively.
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808.07
TERMINATION
A.
Care shall be taken to strip wire without
nicking or damaging the conductors. Frayed, nicked or
missing strands/conductors at the point of termination is not
acceptable.
B.
Where the connection is made to a
terminal block, the ends should be stripped bare between
3/8” and 5/8” in length. For stranded conductors, the ends
shall be twisted lightly and tinned, then inserted into the
opening of the terminal block so that when secured
(tightened), a nominal 1/32” of bared, tinned, wire is visible.
C.
“Spade tongue” insulated crimp
termination are required on “under the head” style screws,
except for Ground connections which shall be “Ring tongue”.
808.08
IDENTIFICATION TAGS ON INSTRUMENTS
A.
Instrument Tags shall be stainless steel,
either engraved or stamped with the Full Instrument Tag
Number.
B.
A Full Instrument Tag Number. For
example PCHW006FQIC-0315
C.
A breakdown of the Instrument Tag
Number structure follows:
PCHW
= Process Chilled Water HGST CAD
Standards MP05-09)
006 = Building Number
FQIC = Flow Totalizing(Q) Indicating Controller (ISA
Standards)
= Spacer
0315 = Sequence Number
D.
The Instrument Tag shall be affixed to
the instrument so that it is visible and easy to read.
E.
The Instrument Tag shall be affixed to
the instrument by a stainless steel “ty-wrap” or other
stainless steel wire method that prevents disassembly of the
Tag from the Instrument.
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***END OF SECTION 16808***
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