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Honeywell T921A, Руководство пользователя

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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.

■

Accessory faceplates available for horizontal mount-
ing of T921A,B,E models.

■

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.

■

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.

■

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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

Содержание T921A

Страница 1: ...ls 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 thermomet...

Страница 2: ... also include the 127246A Adapter Plate As sembly 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 cool heat changeover switch T921E Includes a switch and heater that provide a night setback of approximately 10 F 5 5 C T921F Includes an spd...

Страница 3: ...35B 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 135135Ca a Blank 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 outdo...

Страница 4: ...nduit 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 Mountthethermostatonthebackplatewiththemount ing screws 8 After performing the checkout tests replace the ther mostat cover and tighten the locking screw A...

Страница 5: ...tat before mounting the instrument onto the conduit box Terminal locations for all models are shown in Fig 5 Note the difference in terminal designa tions for the auxiliary switch on the T921F and G The H Heater terminal on the T921E is a black leadwire Typical wiring diagrams are shown in Figs 6 through 10 Wire the T921 color to color when the modulating motor must drive the valve or damper open ...

Страница 6: ...L IS A BLACK LEADWIRE T R W B T B W R H 2 2 TRANSFORMER Fig 8 Typical wiring diagram for T921E L1 HOT L2 1 1 SERIES 90 MODULATING MOTOR T921B M5992 POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED INTERCHANGE B AND W CONNECTIONS TO REVERSE DIRECTION OF MOTOR TRAVEL T R W B T B W R 2 2 TRANSFORMER B W SUMMER COOL WINTER HEAT Setting andAdjusting TEMPERATURE SETTING Adjust a...

Страница 7: ...CATOR LOCK SCREW BELLOWS SETTING ADJUSTMENT KNOB POTENTIOMETER WIPER 1 1 SUMMER WINTER COOL HEAT CHANGEOVER SWITCH ON T921B ONLY NIGHT SETBACK SWITCH ON T921E ONLY M9039 80 70 60 In the T921 a vapor filled bellows moves the potenti ometer wiper by expanding or contracting in proportion to temperature changes As the wiper moves the appropriate motor winding is energized opening or closing the valve...

Страница 8: ...ng applica tion Raise the setpoint gradually the auxiliary switch should make R W before the setting indicator reaches room temperature As the setting indicator moves above room temperature the valve or damper should open 4 If the valve or damper responds properly to the thermostat move the setpoint to the desired temperature M5991 2 5 F 1 5 C SETPOINT TEMPER ATURE 2 5 F 1 5 C R B MAKES TEMPERATUR...

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