Caution – Honeywell Q539A User Manual

Page 2

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Do not mount the subbase where it may be affected by:
— drafts or dead spots behind doors or in corners.
— hot or cold air from ducts.
— radiant heat from the sun, fireplaces, or appliances.
— concealed pipes and chimneys.
— unheated (uncooled) areas such as an outside wall.

CAUTION

• Disconnect power supply to prevent electri­

cal shock or equipment damage.

• Do not short across coil terminals on relay,

this can burn out the thermostat heat
anticipator.

• Do not overtighten captive mounting screws

because damage to subbase threads can result.

MOUNTING AND WIRING

Disconnect power supply before beginning installation to

prevent electrical shock or equipment damage.

All wiring must comply with local codes and ordinances.
1. In replacement applications, check the existing sub­

base wires for cracked or frayed insulation. Replace any
wires in poor condition. If the wire is plastered into the wall,
make a hole next to the wires and loosen the wires so that the
wires can be pushed back into the wall later.

2. In new installations, run wiring (if necessary) to the

subbase location.

IMPORTANT: To prevent interference with the thermostat

linkage, keep wire length to a minimum and run wires
as close as possible to the subbase.

3. Connect the wires to the terminals inside the subbase.

Refer to equipment manufacturer instructions for Q539
wiring diagrams. If not available, refer to Fig. 1 through 5.

4. Push excess wire back through the hole and plug any

opening with insulation to prevent drafts that can affect
performance.

5. Loosely fasten the thermostat subbase to the wall with

a screw through the left mounting hole. Adjust the subbase so
it is approximately level and start the second screw through
the right mounting slot. Do not tighten.

6. Level the thermostat subbase using a spirit level as

shown in Fig. 1.

7. Tighten mounting screws.

IMPORTANT: An incorrectly leveled subbase will cause

the temperature control to deviate from setpoint.

8. Mount and wire the thermostat to the thermostat sub­

base using the equipment manufacturer’s instructions.

Fig. 1—Level Q539 using a spirit level .

SPIRIT
LEVEL

LEVELING
POSTS (2)

MOUNTING
SLOTS

M3319A

OPENING FOR
THERMOSTAT
WIRING

Fig. 2—Barrier configuration.

FOR STRAIGHT
INSERTION–
STRIP 5/16 in. (8 mm)

FOR WRAPAROUND–
STRIP 7/16 in. (11 mm)

SUBBASE TERMINAL SCREW

M8831

BARRIER

Fig. 3—Typical hookup for Q539A in heating­
cooling application with remote lockout
indication.

Q539A/T87F INTERNAL SCHEMATIC

T87F

TEMP.
FALL

R1

ADJUST-
ABLE
HEAT
ANTICIPATOR

FIXED COOL

ANTICIPATOR

LOCKOUT
INDICATOR
LIGHT

HEAT

OFF

COOL HEAT OFF COOL

AUTO

FAN

ON

X

RH

W

Y

G

RC

SWITCH

HEATING
CONTROL

COOLING
CONTROL

FAN
RELAY

HEATING
TRANSFORMER

COOLING
TRANSFORMER

L1

L1

1

1

W1

Y1

L2

L2

(HOT)

(HOT)

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.

M8832

95-6486—9

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1

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