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.
Q539A provides system and fan switching and cooling
anticipator for heating cooling systems. Includes indicator
LOCKOUT LED for use in oil burner systems.
Q539H provides fan switching with Z terminal for low voltage
fan switch to control fan in AUTO position.
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.
TABLE 2—TERMINAL DESIGNATIONS.
Heating Relay or Valve Coil.
Cooling Contactor Coil.
Heating Damper Motor or Changeover
Valve (if used).
Cooling Damper Motor or Changeover
Valve (if used).
Fan Relay Coil.
Clogged Filter Switch or Lockout Switch
Heat Pump Contactor Coil.
Q539H low voltage fan switch for control
of fan relay in AUTO position for both
heating and cooling control.
Cooling transformer in systems with separate heating and
Heating transformer in systems with isolated heating and
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.
®U.S. Registered Trademark
Copyright © 2002 Honeywell •
Q539A, H and J Subbases
Installation Instruction for the Trained Service Technician.
TABLE 1—SUBBASE SPECIFICATIONS.
• All Rights Reserved
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
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
WHEN INSTALLING THIS PRODUCT...
1. Read these instructions carefully. Failure to follow
instructions can damage product or cause a hazardous
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
4. After completing installation check out product opera
tion as provided in these instructions.
Locate the subbase about 5 ft (1.5m) above the floor in
an area with good air circulation at average temperature.