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Q539A, H and J Subbases  
Installation Instruction for the Trained Service Technician.  
Application  
Q539 Subbases provide cooling anticipators, and mounting for T87F Thermostats. Q539 Subbases also provide system  
and fan switching for heating, cooling, and heating-cooling thermostats. For subbase specifications, refer to Tables 1 and 2.  
TABLE 1—SUBBASE SPECIFICATIONS.  
System  
Switch  
Fan  
Switch  
See  
Fig.  
Model Description  
Terminals  
Q539A provides system and fan switching and cooling  
anticipator for heating cooling systems. Includes indicator  
LOCKOUT LED for use in oil burner systems.  
HEAT-  
OFF-  
COOL  
AUTO-ON RH  
-
RC-W-Y-G-X  
3
Q539H provides fan switching with Z terminal for low voltage NONE  
fan switch to control fan in AUTO position.  
AUTO-ON R-W-Y-G-X-Z  
4
5
Q539J provides system switching for control of heating and  
cooling for heat pump and electric heating. Auto fan operates  
through fan relay on both heating and cooling.  
HEAT-  
OFF-  
COOL  
AUTO-ON R-W-Y-G-X-P-O-B  
TABLE 2—TERMINAL DESIGNATIONS.  
Mercury Notice  
Terminal  
R
RCa  
RH b  
W
Connection  
Transformer.  
This control contains mercury in a sealed tube. Do not  
place control in the trash at the end of its useful life.  
If this control is replacing a control that contains mer-  
cury in a sealed tube, do not place your old control in the  
trash.  
Contact your local waste management authority for  
instructions regarding recycling and the proper disposal of  
this control, or of an old control containing mercury in a  
sealed tube.  
Cooling Transformer.  
Heating Transformer.  
Heating Relay or Valve Coil.  
Cooling Contactor Coil.  
Y
Bc  
Heating Damper Motor or Changeover  
Valve (if used).  
Od  
Cooling Damper Motor or Changeover  
Valve (if used).  
G
Xe  
Fan Relay Coil.  
Installation  
Clogged Filter Switch or Lockout Switch  
(
primary control).  
WHEN INSTALLING THIS PRODUCT…  
1. Read these instructions carefully. Failure to follow  
P
Z
Heat Pump Contactor Coil.  
instructions can damage product or cause a hazardous  
condition.  
Q539H low voltage fan switch for control  
of fan relay in AUTO position for both  
heating and cooling control.  
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. Aftercompletinginstallationcheckoutproductopera-  
tion as provided in these instructions.  
a
b
c
d
e
Cooling transformer in systems with separate heating and  
cooling circuits.  
Heating transformer in systems with isolated heating and  
cooling circuits.  
Circuit only completed between R and B with system  
switch in HEAT position.  
Circuit only completed between R and O with system  
switch in COOL position.  
Only available on subbases with indicator LEDs.  
LOCATION  
Locate the subbase about 5 ft (1.5m) above the floor in  
an area with good air circulation at average temperature.  
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• All Rights Reserved  
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Do not mount the subbase where it may be affected by:  
Fig. 1—Level Q539 using a spirit level .  
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.  
SPIRIT  
LEVEL  
LEVELING  
POSTS (2)  
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.  
OPENING FOR  
THERMOSTAT  
WIRING  
MOUNTING  
SLOTS  
M3319A  
Do not overtighten captive mounting screws  
because damage to subbase threads can result.  
MOUNTING AND WIRING  
Disconnectpowersupplybeforebeginninginstallationto  
prevent electrical shock or equipment damage.  
All wiring must comply with local codes and ordinances.  
Fig. 2—Barrier configuration.  
FOR STRAIGHT  
INSERTION–  
STRIP 5/16 in. (8 mm)  
FOR WRAPAROUND–  
STRIP 7/16 in. (11 mm)  
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.  
BARRIER  
2. In new installations, run wiring (if necessary) to the  
M8831  
SUBBASE TERMINAL SCREW  
subbase location.  
IMPORTANT:Topreventinterferencewiththethermostat  
linkage, keep wire length to a minimum and run wires  
as close as possible to the subbase.  
Fig. 3—Typical hookup for Q539A in heating­  
cooling application with remote lockout  
indication.  
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.  
Q539A/T87F INTERNAL SCHEMATIC  
4. Push excess wire back through the hole and plug any  
T87F  
opening with insulation to prevent drafts that can affect  
performance.  
TEMP.  
FALL  
R1  
5
. Loosely fasten the thermostat subbase to the wall with  
ADJUST­  
ABLE  
HEAT  
ascrewthroughtheleftmountinghole.Adjustthesubbaseso  
it is approximately level and start the second screw through  
the right mounting slot. Do not tighten.  
ANTICIPATOR  
W1  
Y1  
6. Level the thermostat subbase using a spirit level as  
shown in Fig. 1.  
FAN  
OFF  
COOL HEAT OFF COOL  
7. Tighten mounting screws.  
AUTO  
ON  
HEAT  
RH  
LOCKOUT  
INDICATOR  
LIGHT  
IMPORTANT: An incorrectly leveled subbase will cause  
the temperature control to deviate from setpoint.  
X
W
Y
G
RC  
8
. Mount and wire the thermostat to the thermostat sub-  
FAN  
RELAY  
base using the equipment manufacturer’s instructions.  
HEATING  
CONTROL  
COOLING  
CONTROL  
SWITCH  
HEATING  
TRANSFORMER  
COOLING  
TRANSFORMER  
1
1
L2 L1  
L2 L1  
(HOT)  
(HOT)  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
M8832  
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Settings  
Fig. 5—Typical hookup for Q539J in heating­  
cooling applications. Fan relay operates  
automatically on heat or cool with fan in AUTO  
position  
SUBBASE SETTING  
The subbase switching positions control the system  
operation as described below.  
SYSTEMSWITCH(somesubbasesdonothaveallofthe  
Q539J/T87F INTERNAL SCHEMATIC  
T87F  
following functions):  
COOL—cooling system is automatically controlled  
by the thermostat. Heating system is off.  
OFF—both the heating and cooling systems are off. If  
the fan switch is at AUTO position, the cooling fan  
is also off.  
HEAT—heating system is automatically controlled  
by the thermostat. Cooling system is off.  
FAN SWITCH:  
TEMP.  
R1 FALL  
FILTER  
LIGHT  
ADJUST­  
ABLE  
HEAT  
ANTICIPATOR  
W1  
Y1  
FAN  
ON  
OFF COOL AUTO  
OFF  
COOL  
ON—fan operates continuously.  
HEAT  
W
HEAT  
B
AUTO—fan operates with cooling equipment as con-  
trolled by the thermostat or with the heating equip-  
ment as controlled by the plenum switch.  
To move the subbase switches to the desired control  
positions, use thumb and index finger to slide lever. Stop  
lever must stop over desired function indicator position for  
proper circuit operation.  
1
R
O
G
P
X
Y
ELECTRIC  
HEAT  
RELAY  
HEATING  
DAMPER  
MOTOR  
FAN  
RELAY  
CLOGGED  
2
FILTER SWITCH  
OR COOLING  
PANEL  
COMPRESSOR  
RELAY  
Fig. 4—Typical hookup for Q539H in heating­  
cooling application with remote switching  
required to select heating or cooling and to  
provide automatic fan operation.  
COOLING  
DAMPER  
MOTOR  
CONNECTION  
Q539H/T87F INTERNAL SCHEMATIC  
3
T87F  
TEMP.  
FALL  
L2 L1  
R1  
(HOT)  
FILTER  
LIGHT  
1
2
X TERMINAL IS USED ON Q539 MODELS WITH FACTORY-  
INSTALLED MALFUNCTION LIGHT.  
ADJUST­  
ABLE  
HEAT  
WITH NO O TERMONAL LOAD, THERMOSTAT CURRENT DURING  
ANTICIPATOR  
HEATING CYCLE VARIES DEPENDING ON WHETHER FAN SWITCH  
IS IN THE ON OR AUTO POSITION. HEATER SHOULD BE SET FOR  
COMBINED CURRENT LEVEL OF HEAT RELAY AND FAN RELAY COILS.  
WITH O TERMINAL LOAD, SET THERMOSTAT HEAT ANTICIPATOR  
TO ITS MAXIMUM SETTING. (LIMIT THE THERMOSTAT HEATING  
LOAD CURRENT TO 0.8 AMPS TO ASSURE GOOD PERFORMANCE.)  
W1  
Y1  
FAN  
AUTO  
ON  
3
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
X
1
PROTECTION AS REQUIRED.  
W
Y
Z
G
R
M8834  
HEAT  
COOL  
REMOTE  
SYSTEM  
SWITCH  
FAN  
RELAY  
Checkout  
CLOGGED  
COOLING  
FILTER SWITCH  
OR COOLING  
PANEL  
CONTACTOR  
COIL  
When installation is complete, turn on power supply and  
check system operation.  
HEATING  
RELAY OR  
VALVE  
CONNECTION  
COIL  
EXTERNAL  
SWITCHING  
FOR AUTO  
FAN  
HEATING  
Move the system switch on the Q539 to HEAT and the  
fan switch to AUTO. Move the heating setpoint dial to about  
6
AC (10AF) above room temperature. Heating equipment  
should start and the fan should run. Change the setpoint to  
about 6AC (10AF) below the room temperature. The heating  
equipment and fan should shut off.  
1
2
X TERMINAL IS USED ON Q539 MODELS WITH  
FACTORY-INSTALLED MALFUNCTION LIGHT.  
2
POWER SUPPLY. PROVIDE DISCONNECT  
MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
L2 L1  
(HOT)  
M8833  
NOTE: In heat pump applications, a minimum off-timer  
provides a five-minute time delay before starting com-  
pressor when the thermostat last turned off the compres-  
sor, or when the system first received power. This delay  
prevents compressor short cycling.  
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COOLING  
FAN  
Move the subbase switch to OFF and the fan switch to  
ON. The fan should run continuously. Move the fan switch  
to AUTO. In this position, fan operation is controlled by the  
heating or cooling system control circuit.  
Operate the entire system one complete cycle with  
switches in each position before leaving installation. Turn  
thermostat dial to the desired setting and set the system and  
fan switches.  
CAUTION  
If outside air or heat exchange medium (water) is  
below 10AC (50AF), do not operate cooling.  
Move the system switch on the Q539 to COOL and the  
fan switch to AUTO. Move the cooling setpoint dial to about  
6
AC (10AF) below room temperature. Cooling equipment  
should start and the fan should run. Change the setpoint to  
about 6AC (10AF) above the room temperature. The cooling  
equipment and fan should shut off.  
Automation and Control Solutions  
Honeywell  
985 Douglas Drive North  
Golden Valley, MN 55422  
Honeywell Limited—Honeywell Limitée  
35 Dynamic Drive  
1
Scarborough, Ontario  
M1V 4Z9  
Printed in U.S.A. on recycled  
paper containing at least 10%  
post-consumer paper fibers.  
95-6486–9 G.H. Rev. 8-02  
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