Honeywell T921A Mode D'emploi

T921A Thermostat provides 3-wire, low voltage pro-
portional control for Series 90 (135 ohm) valve motors,
damper motors, and balancing relays in heating or cooling
system applications. A bellows element adjusts the po-
tentiometer slider to regulate motor operation. The range
for both the setpoint and the thermometer is 10° to 30° C
[50° to 86° F]. The throttling range is approximately 2.5° C
[4.5° F]. The T921A Thermostat has a contemporary cover.
®
The TRADELINE model includes an adapter and a face-
plate for horizontal or vertical mounting on a horizontal
conduit box.
CAUTION
Disconnect power supply before installation to
prevent electrical shock and equipment damage.
WHEN INSTALLING THIS PRODUCT...
1. Installer must be a trained, experienced service
technician.
2. All wiring must comply with applicable electrical
codes, ordinances and regulations.
3. Do not exceed the ratings listed on device nameplate.
4. After the installation is complete, conduct a thor-
ough checkout of the product operation.
LOCATION
Locate the T921A Thermostat about 5m [1.5 ft] above the
floor in an area with good air circulation at average room
temperature.
Do not mount the thermostat where it can be affected by:
— drafts, or dead spots behind doors and in corners.
— hot or cold air from ducts.
— radiant heat from the sun or appliances.
— concealed pipes and chimneys.
— unheated (uncooled) areas such as an outside wall
behind the thermostat.
MOUNTING
1. Disconnect power supply before installation to pre-
vent electrical shock and equipment damage.
2. Loosen the locking screw at the bottom of the case
with an Allen wrench.
3. Lift off the thermostat cover.
Proportioning Thermostats
Application
Installation
J.D. • 3-94 • ©Honeywell Inc. 1994 • Printed in U.S.A. • Form Number 69-0828B
4. Remove the mounting screws that secure the thermo-
stat to the backplate and remove the backplate.
5. Fasten the backplate to the conduit box (see Fig. 1).
Use the 127246A Adapter Plate Assembly (must be or-
dered separately but is included for the TRADELINE
model) to mount the thermostat vertically on the horizontal
conduit box; or to mount the thermostat horizontally on the
vertical conduit box (see Fig. 2).
NOTE: When an accessory adapter plate is used, fasten the
adapter plate to the conduit box with the two screws
provided. Then fasten the backplate to the adapter plate.
6. Make all electrical connections to the terminals on
the back of the thermostat before mounting the instrument
on the backplate. Refer to the Wiring section.
7. Mount the thermostat on the backplate with the mount-
ing screws.
8. When mounting the thermostat horizontally, attach
the accessory faceplate. Peel the backing strip from the
faceplate and place it lightly over the vertical faceplate.
Align the edges and corners and make sure the scales align
with the markings. Press firmly over the entire surface. Do
not attempt to remove and reattach the faceplate once it has
been mounted.
9. After performing the checkout tests, replace the ther-
mostat cover and tighten the locking screw.
Fig. 1—Vertical mounting of T921A Thermo-
stat on vertical conduit box. Thermostat can
also be mounted horizontally on horizontal
conduit box using add-on faceplate.
NOTE: ACCESSORY FACEPLATE FOR USE WHEN
THE THERMOSTAT IS MOUNTED HORIZONTALLY.
PEEL OFF BACKING AND APPLY OVER VERTICAL
FACEPLATE AFTER MOUNTING IS COMPLETE.
1
T921A
MOUNTING
SCREWS
LOCKING
SCREW
COVER
®
CONDUIT
BOX
BACKPLATE
M9037
69-0828B