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60-2242—2
J. D. • Rev. 1-94 • ©Honeywell Inc. 1994 • Form Number 60-2242—2
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.
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Accessory faceplates available for horizontal mount-
ing of T921A,B,E models.
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COOL-HEAT changeover switch in the T921B.
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Night setback mechanism and switch in the T921E.
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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.
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A bellows element adjusts the potentiometer slider
to regulate motor operation.
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Various temperature ranges are available.
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All models are available with a thermometer and a
locking cover.
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T921A
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T921B
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T921E
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T921F
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T921G
CONTENTS
Specifications ................................................. 2
Ordering Information ..................................... 2
Installation ..................................................... 4
Setting and Adjusting ..................................... 7
Operation ....................................................... 7
