User Guide

Copyright 2008, TAC
All brand names, trademarks and registered
trademarks are the property of their respective
owners. Information contained within this
document is subject to change without notice.
F-16441-5
www.tac.com
TAC
1354 Clifford Avenue
P.O. Box 2940
Loves Park, IL 61132-2940
Wiring
The thermostat has one 1/2 in. to 3/4 in. (13 to 19 mm)
conduit opening in the bottom of the housing. Make all
electrical connections in accordance with the job wiring
diagram and in compliance with national and local
electrical codes. Device terminal coding, switch action,
and wiring diagrams are shown in typical applications
in Figure-2 and Figure-3.
Figure-2
Figure-3
Checkout
After installing the thermostat, proceed as follows:
1. With electrical power on and hot water flowing
through the pipe, rotate the setpoint dial from min-
imum to maximum and check operation. If wired-
common and normally closed to fan, the fan will
start at minimum dial setting and stop at maximum
dial setting. The reverse will occur if wired com-
mon to normally open.
2. If no electrical power is available, contact closure
may be checked with an ohmmeter.
3. The differential is factory set to provide the follow-
ing switch action:
a. At 5°F (2.8°C) above the setpoint, a common-
normally closed is made.
b. At 5°F (2.8°C) below the setpoint, a common-
normally open circuit is made.
Run/Adjust
Setpoint
Screwdriver adjustment. Scales are dual marked °F on
front and °C on back. To change scale, remove spring
retainer ring, select scale, and replace retaining ring.
Refer to Checkout for manual operation.
Calibration
1. Disconnect power to the thermostat.
2. Soak the bulb for 10 minutes at a known tempera-
ture.
3. Turn the dial until the thermostat clicks, reverse
the dial until it clicks again.
4. Turn the dial midway between the click points.
5. Turn the calibration nut (located under the dial)
until the temperature of the bulb is indicated on the
dial.
Concealed Setpoint and Lock Cover Screw
Order AT-210 concealed Adjustment Kit separately.
1. Peel off adhesive film from the concealed adjust-
ment plate and place into the recess of the cover.
2. Remove screw from the cover.
3. Install lock cover screw provided with AT-210.
Maintenance
If excessive corrosion develops between the sensing
element and the pipe, clean the pipe and apply a
silicone lubricant such as #6 compound from Dow
Corning Company between the pipe and the sensing
element to prevent additional corrosion.
Repair
Field repair of the thermostat is not recommended. If
the system is not operating properly and the reason is
traced to the thermostat, it should be replaced.
L1
Com
NC
NO
Unit Heater
Fan Motor
L2
Room Thermostat
TC-1101
Common
Rise NC
Drop NO
Typical unit heater application wiring for strap-on thermostat TC-2974
Unit heater fan runs only when heating supply media is above the setpoint of TC-2974
Contact Makes
on Temp.
L1
Common
Rise NC
Drop NO
Typical hot water boiler application wiring for strap-on
thermostat TC-2974. Boiler runs only when water
temperature is below setpoint of TC-2974.
Contact Makes
on Temp.
To Boiler Controls