NELSON 27278-AD, TH7325, TH7325-2, TA7140 Heat Tracing Temerature Switch for Hazardous Locations Owner's manual
- Type
- Owner's manual
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 electrical rating and circuitry
(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.
HEAT TRACING TEMPERATURE SWITCH
FOR HAZARDOUS LOCATIONS
NELSON HEAT TRACING SYSTEMS, Tulsa, OK 74146 Bulletin No. 27278-AD 3-10-08 1 of 3
Installation And Maintenance Instructions
Model TH7325
Line sensing bulb and capillary type
Model
TH7325-2
DPST Relay - Line sensing bulb and
cappilary type
Model
TA7140
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.
Caution: 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 appro-
ximately 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 or heat sinks.
Enclosure: Type NEMA 4.
Enclosure temperature limits:
-40 °F to 140 °F (-40 °C to 60 °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 @ 125,250,480 VAC.
DPST Relay: Coil - 240VAC, 4VA
Contacts - 22A @ 208/240VAC.
Agency Approvals
Hazardous Locations (Division I)
Class I, Groups B,C & D
Class II, Groups E, F & G
Class III
File No. E58658 File No. LR34556
Job Identification 1Z1A0.AE
0081
LCIE 07 ATEX 6093 X
II 2 G D
Ex d IIC T6 *
Ex tD A21 IP6X T80°C*
-40°C < Tamb < +60°C
* Relay Model - T4, T130°C
Wiring (continued)
Electrical Connection:
Clamping screw terminals on insulated terminal block
via 3/4 NPT (female) conduit connection. Use only
copper conductors, 75°C rated for standard SPDT snap
switch models, & 125°C rated for relay model (TH7325-2).
Standard SPDT snap-switch models TH7325 &
TA7140, 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 wire to terminal block:
Purple = Common, Blue = NC, Red = NO
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.
APPROVED
Ø 5/16
4
4 1/2
6 9/16
4 1/2
8
203
MA X
Ø 1/16
4
1 7/32
3/8
F
500
C
50 100
C
F
2
2
8
114
167
114
102
13
102
30
10
51
25
SWITCH NUMBER MEDIA TE
ADJUST ABLE RAN GE
CLASS I
GROUPS: B, C & D
CLASS II
GROUPS: E, F & G
CLASS III
R
TYPE 4
LISTED
366S
TE MPERATURE SWITCH
FM
APP RO V E D
ELECTRICAL RATINGS
THERMOSTAT FOR
HAZARDOUS LOCATIONS.
II 2 G D
00 8 1
EEx d IIC T6
LCIE 02 ATEX 6 206
Tam b -40 %%dC
ELECTRICAL RATING S
REMOTE BULB AND
CAPILLARY MODEL
LOCAL MOUNT MODEL
1 HEX
1/2
(INTERNAL)
HEX
INTERNAL
GROUND SCREW
WITH CLAMP
ADJUSTING KNOB
REMOVE COVER
TO ADJUST
TIGHTEN 4mm SET SCREW
TO LOCK COVER IN PLACE
AFTER FIELD WIRING
EXTERNAL
GROUND
SCREW
WITH
CLAMP
4
102
3/4 NPT
FEMALE
CONDUIT
TERMINAL BLOCK
ACCEPTS #16-#10 AWG
LEAD WIRES
6 FOR RELAY MODEL ONLY
152
Ø 9/32 MOUNTING HOLE 4 PLACES
7
For service or ordering information
Consult factory or authorized factory representative.
Specify full catalog number (with any optional modifica-
tions or factory set-point) as shown on part
number code.
TA7140
15 TO 140 °F (-9 TO 60 °C)
-40 TO 160 °F (-40 TO 71 °C)
SWITCH
NUMBER
BULB SENSOR EXPOSURE
LIMITS (PROOF)
ADJUSTABLE RANGE
TEMPERATURE RANGE
TH7325
25 TO 325 °F (-4 TO 163 °C) -40 TO 420 °F (-40 TO 215 °C)
Warranty
All products of the company are sold and all services
are offered subject to the company's standard condi-
tions of sale.
Causes of improper operation:
1. Incorrect electrical connection: check leads to
switch. 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 switch mounting
and be sure there is no excessive vibration.
DIMENSIONS IN BOXES
ARE IN MILLIMETERS
NELSON HEAT TRACING SYSTEMS, Tulsa, OK 74146 Bulletin No. 27278-AD 3-10-08 2 of 3
TH7325-2
25 TO 325 °F (-4 TO 163 °C) -40 TO 420 °F (-40 TO 215 °C)
Troubleshooting
Warning: Disconnect electrical power supply to
switch before removal or inspection.
Failure to observe this warning could
result in serious injury or switch damage.
Important: The switch is
not field-repairable. In
case of damage, replace entire switch.
If the operation of the switch cannot be corrected
by the above means, consult factory or authorized
factory representative.
1. Verify that the thermostat is suitable for the area where it is to be
installed.
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).
Installation Instructions
Positioning the Sensor Bulb (Line Sensing)
Setting the Thermostat
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.
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
Important: All information, including illustrations, is believed to be reliable. Users, however, should independently evaluate the suitability of each
product for their particular application.
Conduit
drain
90°
Heating cable
Control thermostat bulb
Tape
Tape
Heating cable
Control thermostat bulb
Double traced
Single traced
Installing the Thermostat
NELSON HEAT TRACING SYSTEMS, Tulsa, OK 74146 Bulletin No. 27278-AD 3-10-07 3 of 3
Figure 4. Contactor control
Figure 1. Pipe-sensing
C
NO NC
For switching heat-tracing loads greater than 22 A
or switching multiple heat-tracing circuits.
Ø
G
G
N
Ø
Ø
Heating
Cable
Power
connection
Braid
Control
thermostat
Control
thermostat
GFEPD
C
C
NONC
NO
NC
or
208-V or 240-V supply … 240-V heater
120-V supply … 120-V heater
277-V supply … 240-V heater
Ø
C
G
C
N
A
N
B
N
C
Ø
B
Ø
A
120-V or
277-V
coil
Braid
120- V supply … 120-V heater or
277-V supply … 240-V heater
GFEPD
Figure 2. Low-temperature alarm
C
NO NC
Ø
G
N
Ø
Ø
Alarm
Thermostat bulb
(see "Positioning”
instructions above
for m ounting details)
Control
thermostat
GFEPD
or
208-V or 240-V supply
120-V supply … 120-V heater
277-V supply … 240-V heater
Figure 3. High-temperature alarm
C
NO NC
Ø
G
N
Ø
Ø
Alarm
Control
thermostat
GFEPD
or
208-V or 240-V supply
120-V supply … 120-V heater
277-V supply … 240-V heater
Heating
cable A
Figure 5
. Heat-tracing control
Circuit1
Circuit2
G
Ø Ø
Heating
cable
Power
connection
Braid
Control
thermostat
Relay
GFEPD
Power supply
208-V or 240-V supply … 240-V heater
G
Ø Ø
Thermostat bulb
(see "Positioning”
instructions above
for m ounting details)
Thermostat bulb
(see "Positioning”
instructions above
for m ounting details)
Thermostat bulb
(see "Positioning”
instructions above
for m ounting details)
Thermostat bulb
(see "Positioning”
instructions above
for m ounting details)
Heating
cable B
Heating
cable C
-
1
-
2
-
3
NELSON 27278-AD, TH7325, TH7325-2, TA7140 Heat Tracing Temerature Switch for Hazardous Locations Owner's manual
- Type
- Owner's manual
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