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HEAT TRACING TEMPERATURE SWITCH
FOR ORDINARY AREAS
Model TH4X325
Line sensing bulb and capillary type
Model
capillary type
TH4X325-2
DPST Relay - Line sensing bulb and
Model TA4X140
Ambient sensing probe type
Description
The remote bulb and capillary types are used to
sense the fluid media temperature.
The local mount types are used to sense ambient
temperatures for freeze protection applications.
Installation And Maintenance Instructions
Wiring (continued)
Electrical Connection:
Clamping screw terminals on insulated terminal block
via 3/4 NPT (female) conduit connection. Use 105°C
rated copper conductors only.
Standard SPDT snap-switch models, TH4X325 &
TA4X140, may be wired normally open or normally
closed, per Figures 1 - 4. Contact positions (C, NO,
NC) are clearly identified next to terminal block.
Wire code for built-in jumper wires to terminal block:
Purple= Common
Blue= Normally Closed
Red= Normally Open
Caution: Do not use these switches for hazardous
environments. Sensing bulb and probe
must not exceed specified proof
temperatures.
Installation
Caution: This switch should be installed by a
trained service person.
Switch
Mounting: Switch may be mounted in any position.
Sensors: Install bulb toward the bottom of pipe or
vessel, away from heat sinks and
approximately 90° from the heat tracing
cable. Always secure both bulb and
capillary and wrap with proper insulating
tape. Orient the local mount probe for
optimal ambient temperature sensing
away from heat sources.
Enclosure: Type NEMA 4X .
Enclosure temperature limits:
-40 °F TO 160 °F (-40 °C TO 71 °C).
Wiring
All electrical wiring must comply with local and
national electrical codes.
Caution: Electrical rating must be within range
stated on switch nameplate. Failure to
stay within rating may result in damage
to, or failure of electrical contacts.
Electrical
Rating: Standard Switch: 22A @125,250,480VAC.
DPST Relay: Coil - 240VAC,4VA
Contacts - 22A @ 208/240 VAC.
DPST Relay model TH4X325-2, may be wired per
Fig. 5. Circuit 1 (2 positions) are for first conductor
of heating cable & first phase of power supply.
Circuit 2 (2 positions) are for second conductor of
heating cable & second phase of power supply.
Contact positions for both circuits are clearly identified next to the terminal block. Note that the other
2 positions of the terminal block are not used.
Relay contacts for both circuits are wired to close
on falling (decreasing) temperature.
The braid of heating cable must be connected to the
ground screw provided on every switch.
Testing of the Switch
Testing of the switch may be done before or after
final installation. If bench tested, the switch should
be re-tested when installed in the final application.
Be sure switch can be tested without affecting other
equipment. Check nameplates for elec trical rating
and circui try (normally closed or normally open) of
switch. Cycle switch a few times to check operation.
Set-Point Adjustment
Turn adjustment knob counter-clockwise to increase
set-point.
Agency Approvals
Underwriters Laboratories, Inc.
Temperature Indicating and Regulating
Equipment File No. E56247, Guide No. XAPX.
Canadian Standards Association listed for
Temperature Indicating and Regulating
Equipment File No. LR34555,
Guide No. 400-E-O, Class 4813.
NELSON HEAT TRACING SYSTEMS, Tulsa, OK 74146 Bulletin No. 27277- Z 11-08-07 1 of 3
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Troubleshooting
Warning: Disconnect electrical power supply to
swi tch before removal or inspection.
Failure to observe this warning could
result in serious injury or switch damage.
Important: The swi tch is
not field-repairable. In
case of damage, replace entire swi tch.
Causes of improper operation:
1. Incorrect electrical connection: check leads to
swi tch. Be sure they are properly connected.
See “Wiring” section for circuitry color code.
2. Faulty control circuit: check electrical power
supply to switch. Check for loose or blown
fuses, open-circuited or grounded wires, loose
connections at switch.
3. Incorrect temperature: check temperature in
system. Temperature must be within range
specified on nameplate.
4. Excessive vibration: check for temperature
fluctuations in system. Check swi tch mounting
and be sure there is no excessive vibration.
If the operation of the swi tch cannot be correctedby
the these methods, consult factory or authorized
factory representative.
For service or ordering information
Consult factory or authorized factory representative.
Specify full catalog number (with any optional modifications or fa ctory set-point) as shown on part
number code.
Warranty
All products of the company are sold and all services
are offered subject to the company's standard
conditions of sale.
TEMPERATURE RANGE
SWITCH
MODEL
TA4X140
TH4X325
TH4X325-2 25 TO 325 °F (-4 TO 163 °C)
ADJUSTABLE RANGE
15 TO 140 °F (-9 TO 60 °C)
25 TO 325 °F (-4 TO 163 °C)
BULB SENSOR EXPOSURE
LIMITS (PROOF)
-40 TO 160 °F (-40 TO 71 °C)
-40 TO 420 °F (-40 TO 215 °C)
-40 TO 420 °F (-40 TO 215 °C)
5/16 DIA.
8
7 3/4
197
1/16
DIA.
2
REMOTE BULB
AND CAPILLARY
MODEL
8 approx.
203
4 7/8
124
4 1/2
114
LOCAL MOUNT MODEL
4
102
GROUND
SCREW
5 5/8
4
102
143
4 1/2
114
ADJUSTING KNOB
REMOVE COVER
TO ADJUST
152
TERMINAL
BLOCK
1 1/2
38
FEMALE CONDUIT
9/32 DIA. MOUNTING
7
HOLE, 2 PLACES
6 FOR RELAY
MODEL ONLY
3/4 NPT
3
76
3/8
10
1 5/32
30
13/16
21
LINE SENSING BULB AND
CAPILLARY MODEL
NELSON HEAT TRACING SYSTEMS, Tulsa, OK 74146 Bulletin No. 27277-Z 11-08-07 2 of 3
AMBIENT SENSING PROBE
MODEL
DIMENSIONS IN BOXES
ARE IN MILLIMETERS
Page 3
Installation Instructions
A
A
Installing the Thermostat
1. Verify that the thermostat is suitable for the area where it is to be
installed.
’
DigiTrace
Conduit
drain
2. Check the line voltage and the heat-tracing load to ensure that the
thermostat ratings are not exceeded.
3. Mount the unit in a position that prevents condensation from draining
into the enclosure from the connecting conduit, (see diagram at left).
Positioning the Sensor Bulb
90°
Single Traced
Heating cable
Control thermostat bulb
Tape
Double Traced
Heating cable
Control thermostat bulb
Tape
4. Position the bulb in the lower quadrant of the pipe as shown in the
diagrams to the left. Place the bulb at least three feet from pipe
supports, valves, or other heat sinks; protect the capillary from kinks
or bends less than 1/2 inch in radius.
5. Tape the bulb firmly to the pipe with aluminum tape, making sure
there is no air space between the bulb and pipe. Do not overlap the
bulb and heating cable with the same piece of tape.
Setting the Thermostat 6. Set the thermostat dial to the desired temperature, then finish wiring.
7. Complete insulating. Do not turn the system on until the bulb is
covered with thermal insulation.
8. Fill the piping or tank. Once the thermostat has begun to cycle, check
the fluid temperature with an immersed thermostat (best for plastic
systems) or an accurate temperature indicator. Adjust the dial
setting, if necessary.
Wiring
Power Supply
GFEPD
Ø
208-V or 240-V supply … 240-V cable
Ø
or
G
120-V supply … 120-V cable
Ø
N
277-V supply … 240-V cable
C
NO NC
Power
G
connection
Thermostat bu lb
Braid
(see "Positio ning"
instructions above
for m ounting details)
Heating
Cable
Figure 1. Pipe-sensing
Po wer sup ply
GFEPD
G
208-V or 240-V supply … 240-V heater
Ø Ø
Circuit1
Circuit2
Control
therm ostat
Power Supply
GFEPD
Ø
Ø
208-V or 240-V supply
or
ØGN
120-V or 277-V supply
C
NO NC
Alarm
Thermostat bulb
(see "Positioning"
instructions above
for mounting details)
Figure 2. Low-tem perature alarm
Rela y
Control
thermostat
Power Su pply
GFE PD
Ø
Ø
208-V or 240-V supply
or
ØGN
120-V or 277-V supply
C
NO NC
larm
Thermost at bulb
(see "Positioning"
instructions above
for mounting details)
Figure 3. High-temperature alarm
Control
therm ostat
Power Supply
GFEPD
GCNANBN
C
Braid
Heat ing
cable A
Figure 4. Contactor control
For switching heat-tracing loads greater than 22 A
or switching multiple heat-tracing circuits.
120-V supp ly … 120-V heat ing cable o r
Ø
ØBØ
C
277-V supp ly … 240-V heat ing cable
120-V or
277-V
coil
Heating
cable B
Hea ting
cabl e C
NONC
C
NO
NC
C
Thermosta t bulb
(see "Positioning"
instructions above
for mou nting de tails)
Control
thermostat
Control
thermo stat
Thermostat bulb
(see "Positioning"
instruct ions above
for moun ting details )
Figure 5
. Heat-tracing control
Braid
Heating
cable
GØ Ø
Powe r
connection
Important: All information, including illustrations, is believed to be reliable. Users, however, should independently evaluate the suitability of each
product for their particular application.
NELSON HEAT TRACING SYSTEMS, Tulsa, OK 74146 Bulletin No. 27277-Z 11-08-07 3 of 3
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