Honeywell T451 User Manual download pdf (Page 3)

95C-10903-1

T451, T651 MOTOR-RATED PRECISION THERMOSTATS INSTALLATION

WHEN INSTALLING THIS PRODUCT:

1. Read these instructions carefully. Failure to follow

instructions can damage product or cause a hazardous

condition.

2. Check ratings given in instructions and on product to

make sure product is suitable for your application.

3. Make sure installer is a trained, experienced service

technician.

4. After completing installation, use these instructions to

check out product operation.

WARNING

This thermostat is a line voltage (120 to 277 Vac)

control. Do not install it unless you are completely

familiar and competent with home wiring.

If improperly handled there can be a risk of

240 volt electric shock hazard which may cause

serious injury or death.

CAUTION

1. Disconnect power supply before making wiring

connections to prevent electrical shock or equipment

damage.

2. All wiring must comply with national and local codes

and ordinances.

3. When using aluminum conductors, all wiring connec-

tions to this thermostat must be made to the factory

installed leadwires using approved CO/ALR solderless

connectors. A ﬁre hazard may result otherwise.

4. To avoid handling the sensing element, do not remove

thermostat cover until wiring is completed.

5. Thermostats are designed for use with appliances

having a limit control.

New Installations

1. Install a single-gang electrical box oriented vertically about

4’ to 5’ (1.5 m) above the ﬂoor on an inside wall or pillar

where the thermostat will be subjected to typical room

temperature.

NOTE: To sense temperature properly, the thermostat

must be placed away from concealed warm or cold water

pipes, air ducts, or drafts from hallways, ﬁreplaces or

stairways. Do not place thermostat above convectors or

in the ﬂow from supply fans. Ideally, a thermostat should

be close to the return air path to effectively measure

average room temperature.

2. Wire installation in an approved fashion.

NOTE: T651A and T451A do not feature a Positive Off

setting, and may not be used as a disconnect switch.

3. Leave cover on the thermostat while making wiring

connections. Use solderless connectors approved for the

type, number and gauge of wires being joined.

Connect as per Fig. 2 for the appropriate application.

Fig. 2 — Wiring connections

4. Pre-bend and push leadwires into the electrical junction

box.

5. Hold the thermostat base with one hand and remove the

thermostat cover by grasping two sides of the cover and

pulling outward.

NOTE: If locking cover feature is desired, insert the locking

cover clip in the thermostat base BEFORE mounting the

thermostat on the wall (see Fig. 7).

6. Using the screwdriver, secure the thermostat to the box by

tightening the two mounting screws. Handle thermostat

with care. Excessive pressure may damage the control

knob or sensing element.

IMPORTANT: Before mounting the thermostat, turn the

setting dial to the mid-position (indicator pointing to the

top of the thermostat): this will prevent damage to the

dial stop if the dial is accidentally turned by the screw

driver when the top mounting screw is tightened. Do

NOT press on diaphragm, diaphragm lever arm or

setpoint knob to seat thermostat on the box: thermostat

will be damaged.

Replacement Applications

1. Disconnect power supply before making wiring

connections to prevent electrical shocks or equipment

damage. All wiring must comply with applicable codes

and standards.

2. Remove the old thermostat from the wall, taking care not

to damage the wiring insulation.

3. Check the old insulation for cracks, nicks or fraying. Apply

certiﬁed electrical tape where necessary to insulate wires,

or replace the wires in an approved fashion.

4. Complete installation following steps 3 to 6 in the New

Installations section.

T451A (Heat only)

Heating

Load

Heating

Load

Heating

Load

T651A (Heat only)

T651A (Heat–Cool application)

Cooling

Load

T651A (Cool only application)

Cooling

Load

Heating

Load

T451B (Heat only with positive off)

1 Power supply; provide disconnect means and overload protection as required.

2 Breaks on Positive Off.

3 Exposed unused wires must be properly insulated.

4 Contact makes Black to Red on temperature fall;

Black to Blue on temperature rise.

1 2 3 4

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Honeywell T451 User Manual Page 3

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