Nelson Installation and Maintenance Manual: 27278-AD, TH7325, TH7325-2, TA7140 Heat Tracing Temerature Switch for Hazardous Locations Manuals & Guides

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Page 1

Installation And Maintenance Instructions

HEAT TRACING TEMPERATURE SWITCH

FOR HAZARDOUS LOCATIONS

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.

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.

Testing of the Switch

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.

Testing of the switch may be done before or after final installat ion. If bench tested, the switch should be retested when installed in the final application. Be sure switch can be tested without affecting other equipment. Check nameplates for elec trical 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.

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

APPROVED

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

NELSON HEAT TRACING SYSTEMS, Tulsa, OK 74146 Bulletin No. 27278-AD 3-10-08 1 of 3

Page 2

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.

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 switch mounting

and be sure there is no excessive vibration.

If the operation of the swi tch cannot be corrected by the above means, 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 factory 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

NUMBER

TA7140 TH7325

TH7325-2

ADJUSTABLE RANGE

15 TO 140 °F (-9 TO 60 °C)

25 TO 325 °F (-4 TO 163 °C) -40 TO 420 °F (-40 TO 215 °C)

BULB SENSOR EXPOSURE

LIMITS (PROOF)

-40 TO 160 °F (-40 TO 71 °C)

REMOTE BULB AND

CAPILLARY MODEL

TIGHTEN 4mm SET SCREW

TO LOCK COVER IN PLACE

AFTER FIELD WIRING

Ø 5/16

203

MAX

Ø 1/16

6 9/16

167

4 1/2

114

ADJUSTING K NOB

REMOV E COVER

TO ADJU ST

APPROV E D

THERMOSTAT FOR

HAZARDOUS LOCATIONS.

CLASS I

GROUPS: B, C & D CLASS II

GROUPS: E, F & G

CLASS III

SWITCH NUMBER MEDIA TE

4 1/2

114

TEMPERATURE SWITCH

TYPE 4

LISTED

366S

ADJUSTABLE RA NGE

ELECTRICAL RATINGS

50 100

LOCAL MOUNT MODEL

102

008 1

II 2 G D

EEx d IIC T6

LCIE 02 ATEX 6206 Tamb -40 %%dC

500

DIMENSIONS IN BOXES ARE IN MILLIMETERS

Ø 9/32 MOUNTING HOLE 4 PLACES

102

1/2

(INTERNAL)

HEX

1 HEX

INTERNAL

GROUND SCR EW

WITH CLAMP

TERMINAL BLOCK

ACCEPTS #16-#10 AWG

LEAD WIRES

102

3/4 NPT

FEMALE

CONDUIT

6 FOR RELAY MODEL ONLY

152

1 7/32

3/8

EXT ERNAL

GROUND

SCREW

WIT H

CLAMP

NELSON HEAT TRACING SYSTEMS, Tulsa, OK 74146 Bulletin No. 27278-AD 3-10-08 2 of 3

Page 3

Installation Instructions

Installing the Thermostat

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

Conduit drain

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 (Line Sensing)

Single traced

90°

Heating cable Control thermostat bulb Tap e

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

Double traced

Heating cable Control thermostat bulb Tap e

Setting the Thermostat

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

GFEPD

208-V or 240-V supply … 240-V heater

120-V supply … 120-V heater

277-V supply … 240-V heater

NO NC

Power

connection

Thermostat bulb (see "Positioning”

Braid

instructions above

for mounti ng de tails)

Heating Cable

Figure 1. Pipe-sensing

Power supply

GFEPD

208-V or 240-V supply … 240-V heater

Ø Ø

Power

Ø Ø

connection

Braid

Heating

cable

Circuit1

Circuit2

Control thermostat

Thermostat bulb

(see "Positioning”

instructions above

for mounti ng de tails)

GFEPD

208-V or 240-V supply

ØGN

120-V supply … 120-V heater 277-V supply … 240-V heater

NO N C

Alarm

Thermostat bulb

(see "Positioning”

instructions above

for mounti ng de tails)

Figure 2. Low-temperature alarm

Rela y

Figure 5

. Heat-tracing control

Control thermostat

GFEPD

208-V or 240-V supply

ØGN

120-V supply … 120-V heater 277-V supply … 240-V heater

NO NC

Alarm

Thermostat bulb

(see "Positioning”

instructions above

for mountin g de tails)

Control thermostat

Figure 3. High -tempera ture alarm

GCNANBNCØBØ

Braid

Heating cable A

GFEPD

Heating cable B

120- V supply … 120-V heater or

277-V supply … 240-V heater

120-V or 277-V coil

Heating cable C

NONC

Figure 4. Contactor control

For switching heat-tracing loads greater than 22 A or switching multiple heat-tracing circuits.

Control thermostat

Thermostat bulb (see "Positioning” instructions above for mounti ng de tails)

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. 27278-AD 3-10-07 3 of 3