Download Required Output per Foot (Meter)

Tr o ub le sh o o t in g Gu id el in es
®
PRECISION HEAT AND CONTROL
Chromalox
email: [email protected]
www.chromalox.com
Phone: (412) 967-3800
Fax: (412) 967-5148
Toll-Free: 800-443-2640
103 Gamma Drive
Pittsburgh, PA 15238
USA
PRECISION HEAT AND CONTROL
Chromalox
PJ134
Copyright © 2002-2005, 2010, Chromalox, Inc. All rights reserved.
Frost Heave Prevention Design Guide
Heating cable is drawing proper
current but the floor is heaving.
Possible Causes:
Improper voltage, wrong cable,
wrong design specs, improper
control placement.
Problem:
Heating cable is energized but not
drawing full current.
Possible Causes:
Wrong voltage, damaged cable
(cold zones).
Problem:
Subfloor temperatures are
above normal.
Possible Causes:
Thermostat contacts stuck closed,
thermostat out of calibration,
improper bulb mounting, mixed
control placement.
Problem:
When the circuit breaker is turned
ON, the breaker trips
instantaneously.
Possible Causes:
There is a dead short in the system.
To diagnose where the problem is,
disconnect the power supply wires
from the heating cable at the power
connection box. Attach one lead of a
megaohm device to one bus wire
and the other lead to the
ground braid.
Problem:
Heating cable does not operate.
Possible Causes:
Defective circuit breaker, open
circuit, undersized distribution
wiring, short circuit.
A
Application Guidelines
_________
_________
_________
_________
6.0 (1.8)
Conduit Spacing, ft (m)
4.0 (1.2)
8.0 (2.4)
Required Output per Foot (Meter) R 20 Insulation
2.0 (0.6)
6.0 (1.8)
8.0 (2.4)
Required Output per Foot (Meter) R 30 Insulation
4.0 (1.2)
-20ºF (-29ºC)
-10ºF (-23ºC)
-0ºF (-17ºC)
10ºF (-12ºC)
10.0 (3.0)
-20ºF (-29ºC)
-10ºF (-23ºC)
-0ºF (-17ºC)
10.0 (3.0)
10ºF (-12ºC)
CWM8-1CT
CWM4-2CT
CWM4-1CT
8 (2.4)
8 (2.4)
4 (1.2)
4 (1.2)
240
120
240
120
0.033 (0.010)
0.067 (0.020)
0.017 (0.005)
0.033 (0.010)
480 (146.3)
240 (73.2)
700 (213.4)
350 (106.7)
Concrete
Insulation
Sand
Soil
Contact a Chromalox applications engineer for assistance with heat trace
panel specifications.
For larger loads, both of the above can serve as pilot duty to drive a
remote device. For example, the THR thermostat can be used to
energize the main contactor coil in the WeatherTrace FPAS panel.
2. Electronic control with RTD sensor (CMS). Provides a 20 Amp relay to
240 Vac. Optional alarm output for low-temperature condition.
Straightforward, easy setup and operation. Switch-selectable output
includes on/off or PI control. Sensor should be placed in conduit
centered between heat tracing conduits. See Freezer Floor Frost Heave
Prevention Circuit Layout Options under C, Installation Details.
1. Mechanical thermostatic control (ON/OFF, THR). Heating cable system
turns on and off based on sub-floor temperature. Switches up to 22
Amps. Sensor should be placed in conduit centered between heat
tracing conduits. See Freezer Floor Frost Heave Prevention Circuit
Layout Options under C, Installation Details.
C o n t r o l Op t i o n s
There are two basic ways to control the frost heave prevention system:
L ay o u t C o n s i d er a t i o n s
• Only one run of heating cable is permitted per conduit
• Layout should be arranged to uniformly cover the area to be heated
• Do not cross expansion joints, crack control joints, etc.
• Do not place conduit closer than 4 inches (10 centimeters) to the edge
of the sub-floor, drains, or other obstructions
• When the total length of two or more circuits is less than the
maximum circuit length of the circuit breaker size used, the circuits
may be wired in parallel
En d a n d C o m p o n en t A l l o w a n c es
End allowance is typically 4 feet (1.2 meters) per end (length of cable in
conduit between floor and junction box). Component allowance should be
2 feet (0.6 meters) per end and is the length of the cable inside the junction box. Optionally, the heating cable may be run between junction boxes.
In this case, the end and component allowance would be the center-tocenter distance between conduits.
M a x i m u m C i r c u i t Len g t h
Typically, heating cable layout is a straight-run design. Cable is run the
length of the longest side of the freezer unless this exceeds the
maximum circuit length for that cable wattage and voltage. See the CWM
Cable Specifications table for maximum footage lengths.
Area of floor to be heated (ft/m)
Conduit spacing (ft/m) + End Allowances (ft/m) + Component allowances (ft/m)
4. Estimate the length of cable required for your layout:
Circuit Length and Control Scheme
When water in soil underneath freezers and cold rooms freezes an icy
mass can develop that can cause the floor to heave. Installing Chromalox
CWM cable in the sub-floor under the freezer floor insulation (see the
accompanying illustration) can prevent frost heave by maintaining the
temperature of the ground above freezing. The sub-floor may be concrete
or compacted sand. Typically, the cable is installed in conduit for ease
of repair or retrofit. The conduit is spaced 2 to 8 feet (0.6 to 2.4 meters)
apart, depending on the ambient temperature of the freezer and the
R-value of the insulation. However, 6-foot (1.8-meter) spacing can be
used for freezer temperatures of 0°F (-18°C) and above.
B
Minimum freezer temperature
Insulation R value
Conduit spacing
Voltage supply
-10°F
(-23ºC)
_________
R-20
_________
4 ft (1.2 m)
_________
240V
_________
1. To begin designing your frost heave prevention system, determine
the following information:
Example:
Minimum freezer temperature
Insulation R value
Conduit spacing
Voltage supply
25.0 (7.5)
20.0 (6.0)
15.0 (4.5)
10.0 (3.0)
5.0 (1.5)
25.0 (7.5)
20.0 (6.0)
15.0 (4.5)
10.0 (3.0)
5.0 (1.5)
2.0 (0.6)
Conduit Spacing, ft (m)
Consult the CWM Cable Specifications table for the CWM cable
available and the typical power output for this application.
Example:
CWM8-2CT with a power output of 8 W/ft (2.4 W/m) at 240V
should be used.
CWM8-2CT
CWM Cable Specifications
Model
Output
Output Voltage Circuit Load
Max Circuit
W/ft (W/m)
(Vac)
Amp/ft (Amp/m) Length, ft (m)
3.
Example:
Based on the above design information, the required cable
output is 5.1 W/ft (1.6 W/m).
2. Determine the required power output per foot of cable using
the graphs below. The graphs show required power output for
R values of 20 and 30.
Cable Power Required, W/ft (W/m)
Cable Power Required, W/ft (W/m)
®
Problem:
FROST HEAVE PREVENTION
A
Application Guidelines
B
Minimum freezer temperature
Insulation R value
Conduit spacing
Voltage supply
_________
_________
_________
_________
Sand
Soil
Example:
Minimum freezer temperature
Insulation R value
Conduit spacing
Voltage supply
-10°F
(-23ºC)
_________
R-20
_________
4 ft (1.2 m)
_________
240V
_________
4. Estimate the length of cable required for your layout:
M a x i m u m C i r c u i t Len g t h
Typically, heating cable layout is a straight-run design. Cable is run the
length of the longest side of the freezer unless this exceeds the
maximum circuit length for that cable wattage and voltage. See the CWM
Cable Specifications table for maximum footage lengths.
En d a n d C o m p o n en t A l l o w a n c es
End allowance is typically 4 feet (1.2 meters) per end (length of cable in
conduit between floor and junction box). Component allowance should be
2 feet (0.6 meters) per end and is the length of the cable inside the junction box. Optionally, the heating cable may be run between junction boxes.
In this case, the end and component allowance would be the center-tocenter distance between conduits.
Example:
Based on the above design information, the required cable
output is 5.1 W/ft (1.6 W/m).
Required Output per Foot (Meter) R 20 Insulation
Cable Power Required, W/ft (W/m)
Insulation
Area of floor to be heated (ft/m)
Conduit spacing (ft/m) + End Allowances (ft/m) + Component allowances (ft/m)
2. Determine the required power output per foot of cable using
the graphs below. The graphs show required power output for
R values of 20 and 30.
25.0 (7.5)
20.0 (6.0)
-20ºF (-29ºC)
-10ºF (-23ºC)
15.0 (4.5)
-0ºF (-17ºC)
10ºF (-12ºC)
10.0 (3.0)
L ay o u t C o n s i d er a t i o n s
• Only one run of heating cable is permitted per conduit
• Layout should be arranged to uniformly cover the area to be heated
• Do not cross expansion joints, crack control joints, etc.
• Do not place conduit closer than 4 inches (10 centimeters) to the edge
of the sub-floor, drains, or other obstructions
• When the total length of two or more circuits is less than the
maximum circuit length of the circuit breaker size used, the circuits
may be wired in parallel
C o n t r o l Op t i o n s
There are two basic ways to control the frost heave prevention system:
5.0 (1.5)
2.0 (0.6)
4.0 (1.2)
6.0 (1.8)
8.0 (2.4)
10.0 (3.0)
Conduit Spacing, ft (m)
Required Output per Foot (Meter) R 30 Insulation
25.0 (7.5)
20.0 (6.0)
-20ºF (-29ºC)
-10ºF (-23ºC)
15.0 (4.5)
-0ºF (-17ºC)
10ºF (-12ºC)
10.0 (3.0)
5.0 (1.5)
2.0 (0.6)
4.0 (1.2)
6.0 (1.8)
8.0 (2.4)
10.0 (3.0)
Conduit Spacing, ft (m)
3.
Concrete
Circuit Length and Control Scheme
1. To begin designing your frost heave prevention system, determine
the following information:
Cable Power Required, W/ft (W/m)
FROST HEAVE PREVENTION
Copyright © 2002-2005, 2010, Chromalox, Inc. All rights reserved.
email: [email protected]
www.chromalox.com
103 Gamma Drive
Pittsburgh, PA 15238
USA
PRECISION HEAT AND CONTROL
Chromalox
Possible Causes:
Problem:
Possible Causes:
Problem:
Possible Causes:
Problem:
Possible Causes:
Problem:
Possible Causes:
®
Phone: (412) 967-3800
Fax: (412) 967-5148
Toll-Free: 800-443-2640
Defective circuit breaker, open
circuit, undersized distribution
wiring, short circuit.
Heating cable does not operate.
There is a dead short in the system.
To diagnose where the problem is,
disconnect the power supply wires
from the heating cable at the power
connection box. Attach one lead of a
megaohm device to one bus wire
and the other lead to the
ground braid.
When the circuit breaker is turned
ON, the breaker trips
instantaneously.
Thermostat contacts stuck closed,
thermostat out of calibration,
improper bulb mounting, mixed
control placement.
Subfloor temperatures are
above normal.
Wrong voltage, damaged cable
(cold zones).
Heating cable is energized but not
drawing full current.
Improper voltage, wrong cable,
wrong design specs, improper
control placement.
Heating cable is drawing proper
current but the floor is heaving.
Problem:
Tr o ub le sh o o t in g Gu id el in es
PJ134
Frost Heave Prevention Design Guide
PRECISION HEAT AND CONTROL
Chromalox
®
When water in soil underneath freezers and cold rooms freezes an icy
mass can develop that can cause the floor to heave. Installing Chromalox
CWM cable in the sub-floor under the freezer floor insulation (see the
accompanying illustration) can prevent frost heave by maintaining the
temperature of the ground above freezing. The sub-floor may be concrete
or compacted sand. Typically, the cable is installed in conduit for ease
of repair or retrofit. The conduit is spaced 2 to 8 feet (0.6 to 2.4 meters)
apart, depending on the ambient temperature of the freezer and the
R-value of the insulation. However, 6-foot (1.8-meter) spacing can be
used for freezer temperatures of 0°F (-18°C) and above.
Consult the CWM Cable Specifications table for the CWM cable
available and the typical power output for this application.
Example:
CWM8-2CT with a power output of 8 W/ft (2.4 W/m) at 240V
should be used.
CWM Cable Specifications
Model
Output
Output Voltage Circuit Load
Max Circuit
W/ft (W/m)
(Vac)
Amp/ft (Amp/m) Length, ft (m)
CWM4-1CT
4 (1.2)
120
0.033 (0.010)
350 (106.7)
CWM4-2CT
4 (1.2)
240
0.017 (0.005)
700 (213.4)
CWM8-1CT
8 (2.4)
120
0.067 (0.020)
240 (73.2)
CWM8-2CT
8 (2.4)
240
0.033 (0.010)
480 (146.3)
1. Mechanical thermostatic control (ON/OFF, THR). Heating cable system
turns on and off based on sub-floor temperature. Switches up to 22
Amps. Sensor should be placed in conduit centered between heat
tracing conduits. See Freezer Floor Frost Heave Prevention Circuit
Layout Options under C, Installation Details.
2. Electronic control with RTD sensor (CMS). Provides a 20 Amp relay to
240 Vac. Optional alarm output for low-temperature condition.
Straightforward, easy setup and operation. Switch-selectable output
includes on/off or PI control. Sensor should be placed in conduit
centered between heat tracing conduits. See Freezer Floor Frost Heave
Prevention Circuit Layout Options under C, Installation Details.
For larger loads, both of the above can serve as pilot duty to drive a
remote device. For example, the THR thermostat can be used to
energize the main contactor coil in the WeatherTrace FPAS panel.
Contact a Chromalox applications engineer for assistance with heat trace
panel specifications.
Controls & Accessories
FPAS Freeze Protection
Heat Trace Panel
PJB Rain-Tight
Junction Box
FPAS freeze protection heat trace panels
offer power-distribution, ground-fault
protection, individual circuit-alarming,
and ambient-sensing control for groups
of heat trace circuits with an external
controller/thermostat. The panels are
standard NEMA 4 enclosures for indoor
or outdoor applications. NEMA 4X 304
stainless steel enclosures are available
for harsh environments.
Watertight polycarbonate enclosure for use
with the SSK junction box connection kit.
SSK Junction Box Connection Kit
A complete kit with everything necessary to connect CWM cable
to customer-supplied wiring, including:
• Compression fitting (1)
• Tube of RTV sealant (1)
• 1-inch (25-millimeter)
locknut (1)
• Silicone boot (1)
• O-ring (1)
• Pipe standoff (1)
• Uninsulated barrel connectors (2)
• Self-regulating cable grommet (1)
• Constant-wattage cable grommet (1)
• Insulated barrel connectors (2)
The 3⁄4-inch (19-millimeter) conduit connection fitting will connect
the conduit containing the heating cable to a customersupplied junction box or Chromalox PJB
rain-tight junction box.
Line-Sensing
Thermostat THR
The THR remote-mount thermostat
employs a stainless steel bulb and
capillary design to accurately sense
temperature at key points along the
heating cable. The NEMA 4X enclosure
is epoxy coated to seal from moisture
and contaminants. Switch output is one
SPDT with a 22-amp electrical rating. The
bulb is 115⁄8 inches (29.5 centimeters)
long with a 1⁄8-inch (0.3-centimeter)
outside diameter.
F r ee z e r Fl o o r F r o s t H ea v e P r ev e n t i o n Cr o s s S e c t i o n
Floor
Insulation
Subfloor
Floor
Insulation
Soil
Subfloor
Fr e ez e r F l o o r Fr o s t H e a v e P r e v en t i o n C i r c u i t L a y o u t O p t i o n s
Power Connection
End of Circuit
Power Connection
End of Circuit
Sensor
in
Conduit
Sensor
in
Conduit
Heating Cable Conduits – 1 inch (25.4 millimeters)
Hairpin Layout
Heating Cable Conduits – 1 inch (25.4 millimeters)
Hairpin Layout
I m p o r t a n t S a fe g u a r d s
• Inspect all junction box, connection
box, and sensor connections
• Verify all circuits have been properly
grounded
• Verify all circuits are connected to
proper panel locations
• Verify proper circuit breakers are in
place (always use 30mA trip GFI
type breakers)
• Verify all proper safety warnings are
in place
• Always use ground fault circuit
breakers (30mA trip level)
El ec t r ic a l Tes t s
• Insulation resistance (Megger)
Before pulling cable
After pulling cable
After installing terminations
Before energizing system
• Circuit voltage
• Initial current
I n s t a ll a t i o n Tip s
To o ls Need ed
• Wire cutters
• Megger
• Phillips head screwdriver
• Standard screwdriver
• Voltmeter
• Do not twist buss wires together
at end of circuit
• Insulate all conductive parts
• Seal all electrical connections
against moisture
• Seal ends of exposed cable during
installation
Tr o ub le sh o o t in g Gu id el in es
®
PRECISION HEAT AND CONTROL
Chromalox
email: [email protected]
www.chromalox.com
Phone: (412) 967-3800
Fax: (412) 967-5148
Toll-Free: 800-443-2640
103 Gamma Drive
Pittsburgh, PA 15238
USA
PRECISION HEAT AND CONTROL
Chromalox
PJ134
Copyright © 2002-2005, 2010, Chromalox, Inc. All rights reserved.
Frost Heave Prevention Design Guide
Heating cable is drawing proper
current but the floor is heaving.
Possible Causes:
Improper voltage, wrong cable,
wrong design specs, improper
control placement.
Problem:
Heating cable is energized but not
drawing full current.
Possible Causes:
Wrong voltage, damaged cable
(cold zones).
Problem:
Subfloor temperatures are
above normal.
Possible Causes:
Thermostat contacts stuck closed,
thermostat out of calibration,
improper bulb mounting, mixed
control placement.
Problem:
When the circuit breaker is turned
ON, the breaker trips
instantaneously.
Possible Causes:
There is a dead short in the system.
To diagnose where the problem is,
disconnect the power supply wires
from the heating cable at the power
connection box. Attach one lead of a
megaohm device to one bus wire
and the other lead to the
ground braid.
Problem:
Heating cable does not operate.
Possible Causes:
Defective circuit breaker, open
circuit, undersized distribution
wiring, short circuit.
A
Application Guidelines
_________
_________
_________
_________
6.0 (1.8)
Conduit Spacing, ft (m)
4.0 (1.2)
8.0 (2.4)
Required Output per Foot (Meter) R 20 Insulation
2.0 (0.6)
6.0 (1.8)
8.0 (2.4)
Required Output per Foot (Meter) R 30 Insulation
4.0 (1.2)
-20ºF (-29ºC)
-10ºF (-23ºC)
-0ºF (-17ºC)
10ºF (-12ºC)
10.0 (3.0)
-20ºF (-29ºC)
-10ºF (-23ºC)
-0ºF (-17ºC)
10.0 (3.0)
10ºF (-12ºC)
CWM8-1CT
CWM4-2CT
CWM4-1CT
8 (2.4)
8 (2.4)
4 (1.2)
4 (1.2)
240
120
240
120
0.033 (0.010)
0.067 (0.020)
0.017 (0.005)
0.033 (0.010)
480 (146.3)
240 (73.2)
700 (213.4)
350 (106.7)
Concrete
Insulation
Sand
Soil
Contact a Chromalox applications engineer for assistance with heat trace
panel specifications.
For larger loads, both of the above can serve as pilot duty to drive a
remote device. For example, the THR thermostat can be used to
energize the main contactor coil in the WeatherTrace FPAS panel.
2. Electronic control with RTD sensor (CMS). Provides a 20 Amp relay to
240 Vac. Optional alarm output for low-temperature condition.
Straightforward, easy setup and operation. Switch-selectable output
includes on/off or PI control. Sensor should be placed in conduit
centered between heat tracing conduits. See Freezer Floor Frost Heave
Prevention Circuit Layout Options under C, Installation Details.
1. Mechanical thermostatic control (ON/OFF, THR). Heating cable system
turns on and off based on sub-floor temperature. Switches up to 22
Amps. Sensor should be placed in conduit centered between heat
tracing conduits. See Freezer Floor Frost Heave Prevention Circuit
Layout Options under C, Installation Details.
C o n t r o l Op t i o n s
There are two basic ways to control the frost heave prevention system:
L ay o u t C o n s i d er a t i o n s
• Only one run of heating cable is permitted per conduit
• Layout should be arranged to uniformly cover the area to be heated
• Do not cross expansion joints, crack control joints, etc.
• Do not place conduit closer than 4 inches (10 centimeters) to the edge
of the sub-floor, drains, or other obstructions
• When the total length of two or more circuits is less than the
maximum circuit length of the circuit breaker size used, the circuits
may be wired in parallel
En d a n d C o m p o n en t A l l o w a n c es
End allowance is typically 4 feet (1.2 meters) per end (length of cable in
conduit between floor and junction box). Component allowance should be
2 feet (0.6 meters) per end and is the length of the cable inside the junction box. Optionally, the heating cable may be run between junction boxes.
In this case, the end and component allowance would be the center-tocenter distance between conduits.
M a x i m u m C i r c u i t Len g t h
Typically, heating cable layout is a straight-run design. Cable is run the
length of the longest side of the freezer unless this exceeds the
maximum circuit length for that cable wattage and voltage. See the CWM
Cable Specifications table for maximum footage lengths.
Area of floor to be heated (ft/m)
Conduit spacing (ft/m) + End Allowances (ft/m) + Component allowances (ft/m)
4. Estimate the length of cable required for your layout:
Circuit Length and Control Scheme
When water in soil underneath freezers and cold rooms freezes an icy
mass can develop that can cause the floor to heave. Installing Chromalox
CWM cable in the sub-floor under the freezer floor insulation (see the
accompanying illustration) can prevent frost heave by maintaining the
temperature of the ground above freezing. The sub-floor may be concrete
or compacted sand. Typically, the cable is installed in conduit for ease
of repair or retrofit. The conduit is spaced 2 to 8 feet (0.6 to 2.4 meters)
apart, depending on the ambient temperature of the freezer and the
R-value of the insulation. However, 6-foot (1.8-meter) spacing can be
used for freezer temperatures of 0°F (-18°C) and above.
B
Minimum freezer temperature
Insulation R value
Conduit spacing
Voltage supply
-10°F
(-23ºC)
_________
R-20
_________
4 ft (1.2 m)
_________
240V
_________
1. To begin designing your frost heave prevention system, determine
the following information:
Example:
Minimum freezer temperature
Insulation R value
Conduit spacing
Voltage supply
25.0 (7.5)
20.0 (6.0)
15.0 (4.5)
10.0 (3.0)
5.0 (1.5)
25.0 (7.5)
20.0 (6.0)
15.0 (4.5)
10.0 (3.0)
5.0 (1.5)
2.0 (0.6)
Conduit Spacing, ft (m)
Consult the CWM Cable Specifications table for the CWM cable
available and the typical power output for this application.
Example:
CWM8-2CT with a power output of 8 W/ft (2.4 W/m) at 240V
should be used.
CWM8-2CT
CWM Cable Specifications
Model
Output
Output Voltage Circuit Load
Max Circuit
W/ft (W/m)
(Vac)
Amp/ft (Amp/m) Length, ft (m)
3.
Example:
Based on the above design information, the required cable
output is 5.1 W/ft (1.6 W/m).
2. Determine the required power output per foot of cable using
the graphs below. The graphs show required power output for
R values of 20 and 30.
Cable Power Required, W/ft (W/m)
Cable Power Required, W/ft (W/m)
®
Problem:
FROST HEAVE PREVENTION