T921A,B,E-G Proportional
Control Thermostats
T921 Thermostats provide 3-wire, low voltage proportional control for Series 90 (135 ohm) valve motors, damper motors, and balancing relays in heating or cooling system applications.
■ T921A |
■ T921B |
■ T921E |
■ T921F |
■ T921G |
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■Accessory faceplates available for horizontal mounting of T921A,B,E models.
■COOL-HEAT changeover switch in the T921B.
■Night setback mechanism and switch in the T921E.
■A spdt (single pole double throw) Class 2 auxiliary switch in the T921F,G, which operates at the low (T921F) and high (T921G) end of the throttling range.
■A bellows element adjusts the potentiometer slider to regulate motor operation.
■Various temperature ranges are available.
■All models are available with a thermometer and a locking cover.
CONTENTS |
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Specifications ................................................. |
2 |
Ordering Information ..................................... |
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Installation ..................................................... |
4 |
Setting and Adjusting ..................................... |
7 |
Operation ....................................................... |
7 |
J. D. • Rev. 11-94 • ©Honeywell Inc. 1994 • Form Number 60-2242—2
T921A,B,E-G
SPECIFICATIONS • ORDERING INFORMATION
Specifications
TRADELINE® MODELS
TRADELINE® models are selected and packaged to provide ease of stocking, ease of handling and maximum replacement value. TRADELINE® model specifications are the same as those of the standard models except as noted below.
TRADELINE® MODEL AVAILABLE:
T921A Thermostat for vertical or horizontal mounting.
TEMPERATURE RANGE AND SCALE: 56° to 84° F [13° to 29°].
ADDITIONAL FEATURES:
•TRADELINE® packed with cross-reference label and special TRADELINE® instructions.
•T6051A may be used in electric heat systems.
•They all include slotted sides and an add-on faceplate to allow the thermostat to be mounted horizontally. They also include the 127246A Adapter Plate Assembly for vertical mounting on a horizontal conduit box or for horizontal mounting on a vertical conduit box.
STANDARD MODEL
MODELS:
T921A: Heating or cooling applications.
T921B: Is the same as the T921A but includes a coolheat changeover switch.
T921E: Includes a switch and heater that provide a night setback of approximately 10° F [5.5° C].
T921F: Includes an spdt low voltage Class 2 auxiliary switch that operates at the low end of the throttling range.
T921G: Includes an spdt low voltage Class 2 auxiliary switch that operates at the high end of the throttling range.
SETTING ADJUSTMENT RANGE: T921A,B,E-G: 56° to 84° F [13° to 29° C]. T921A,B,E-G: 13° to 29° C [56° to 84° F]. T921A: 42° to 75° F [ 5° to 24° C]. T921A,B: 66° to 95° F [19° to 35° C].
THERMOMETER: Bimetal. Scale ranges T921A only: 45° to 75° F [7° to 24° C]. All other models: 60° to 90° F [16° to 32° C], 15° to 35° C [59° to 95° F]. T921A is also
available with a blank cover and no thermometer. AUXILIARY SWITCH DIFFERENTIAL:
T921F: 2° F [1° C]. T921G: 1° F [0.5° C].
THROTTLING RANGE: Fixed.
T921A: 2.5° F [1° C] midscale. T921B,E: 4° F [2° C].
T921F: 6° F [3° C]. T921G: 5° F [2.5° C].
Variable.
T921A model available with potentiometer for 5° to 6° F [2.5 to 3° C] throttling range.
ELECTRICAL RATINGS: Voltage: 24 to 30 Vac.
Auxiliary Switch Contact Rating (When Used For Pilot Duty): 100 VA at 30 Vac.
DIMENSIONS: Refer to Fig. 1.
ACCESSORIES (ORDER SEPARATELY):
127246A Adapter Plate Assembly for mounting all models vertically on a horizontal conduit box. (T921 models are shipped with a faceplate for vertical mounting.)
When mounting the T921A,B,E horizontally, see Table 1 to order the faceplate with the appropriate scale. NOTE: Do not mount the T921F,G horizontally.
34297B Thermostat Guard Assembly and 138541A Mounting Plate.
133722A Thermostat Guard (clear plastic cover).
133723A Thermostat Guard (beige plastic cover).
Ordering Information
When purchasing replacement and modernization products from your TRADELINE® wholesaler or your distributor, refer to the TRADELINE® Catalog or price sheets for complete ordering number or specify—
1.Model number.
2.Scale range.
3.Accessories, if desired.
If you have additional questions, need further information, or want to comment on our products or services, please write or phone:
1.You local Honeywell Home and Building Control Sales Office (check the white pages of the phone directory).
2.Home And Building Control Customer Satisfaction Honeywell Inc., 1885 Douglas Drive North Minneapolis, Minnesota 55422 1-800-468-1502
(In Canada—Honeywell Limited/Honeywell Limitee, 740 Ellesmere Road, Scarborough, Ontario M1P 2V9) International Sales and Service Offices in all Principal Cities of the world. Manufacturing in Australia, Canada, Finland, France, Germany, Japan, Mexico, Netherlands, Spain, Taiwan, United Kingdom, U.S.A.
60-2242—2 |
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Fig. 1—T921 approximate installation dimensions in in. [mm].
ACCESSORY ADAPTER PLATE (127246A) FOR |
SETTING |
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MOUNTING ON HORIZONTAL CONDUIT BOX |
ADJUSTMENT |
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HORIZONTAL CONDUIT BOX |
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2-11/16 [69] INCHES FOR |
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T921F, G MODELS. |
M9107 |
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TABLE 1—ACCESSORY FACEPLATE.
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Scale |
Part No. |
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56° to 84° F [13° to 29° C] |
135135A |
13° to 29° C [56° to 84° F] |
135135B |
42° to 75° F [5° to 24° C] |
135135C |
66° to 95° F [19° to 35° C] |
135135D |
56° to 84° F [13° to 29° C] |
135135C a |
aBlank faceplate.
REPLACEMENT PART: 130224 Locking Cover Knob.
OPTIONAL SPECIFICATION (USING THE T991B): Alternate proportional control similar to the T921A, but
uses an outdoor temperature, automatic control point
reset.
T991B with 3-1/2: 1 reset and 50° to 120° F [10° to 49° C] temperature setting scale (when the outdoor bulb is at 60° F [16° C]).
DIMENSIONS: Refer to Fig. 2.
ACCESSORIES:
Compression fittings, immersion wells: Refer to the appropriate specification or the TRADELINE® Catalog.
314439 Mounting Clips: For mounting a capillary tubing (averaging element) in a duct.
T921A,B,E-G
SPECIFICATIONS
7640HX Averaging Element Mounting Kit: For mounting in existing installations where access to the duct is impractical.
Q615A Enclosure: To protect the device when mounted outside; splash proof.
801534 Calibration Wrench.
107324A Bulb Holder: For mounting the bulb in a duct. 34886A Outdoor Bulb Shield: To protect the outdoor
bulb mounting.
Fig. 2—T991B approximate installation dimensions in in. [mm].
15
16
[24]
KNOCKOUT FOR 1/2 INCH
CONDUIT (BOTH ENDS)
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DIAMETER |
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1
2
1OUTDOOR BULB SIZE VARIES INVERSELY WITH THE RESET RATIO.
2INDOOR BULB LENGTH AND DIAMETER IS 4-1/2 [114] INCH BY 1/2 [13] INCH EXCEPT FOR THE AVERAGING ELEMENT WHICH IS 1/8 [3] INCH DIAMETER BY 12 FT. [3 M] LONG.
3 CLEARANCE NECESSARY TO REMOVE COVER. |
M9108 |
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60-2242—2 |
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