Heating, Cooling and Heating/Cooling
Thermostat, Wallplate, and Subbase;
Check thermostat and subbase (if used) suitability for the
heating, cooling, or heating/cooling system. Refer to Table 1.
Assemble tools required: flat bladed screwdriver, hand or
power drill with 3/16-in. drill bit, wire cutter/stripper or
sharp knife, bubble level or plumb bob and line.
Assure power is off to the heating, cooling, or heating/
cooling system at the main fuse panel. Most buildings have
a separate switch box or circuit breaker for disconnecting
power to the heating and cooling (if applicable) equipment.
This thermostat is compatible with most heating, cooling
or heating/cooling systems. Refer to Table 1 for thermostat
and system compatibility information.
Type of Heating System
to be Controlled
Electric (Line Voltage)—
typical baseboard and radiant
Fan Coil Unit
Gas—Direct Spark Ignition
(DSI), Intermittent Pilot (IP),
and Standing Pilot (SP)
Hot Water Zone
Warm Air Zone
If thermostat is not compatible with the system being controlled, the system will not operate. No hazard exists. The thermo-
stat will not be damaged unless it is used to directly control a line voltage system. For proper system operation, a Honeywell
R841 or R8239D1015 Isolating Relay must be added to the thermostat control circuit.
Consult manufacturer for installation requirements.
Thermostat and Wallplate
Installation Instructions for the Trained Service Technician.
TABLE 1—SYSTEM COMPATIBILITY.
• The R8239D1015 Isolating Relay or R841 Silent Switching Center must be
installed in the thermostat control circuit.
• Compatible. Assure correct subbase identity is selected for fan control.
• Compatible. If not using battery backup, assure that 24V control transformer
common is accessible for connection to thermostat cable conductor and power to
the transformer is not regularly interrupted by high temperature or limit operation.
• Compatible. Assure correct subbase identity is selected for fan control and
changeover control (O terminal for cool and B terminal for heat).
• Honeywell 2-wire valves are compatible.
• Some non-Honeywell 2-wire valves require an R8239D1015 Isolating Relay in
the thermostat control circuit.
• Some 3-wire valves require an R8239A1052 Isolating Relay in the thermostat
• If not using battery backup, assure that the 24V control transformer common is
accessible for connection to thermostat cable conductor and power to transformer
is not regularly interrupted by high temperature, purge cycle, or limit operation.
• Honeywell damper motors are compatible.
• Some non-Honeywell damper motors require an R8239D1015 Isolating Relay in
the thermostat control circuit.
• Most are compatible.
D.F. • Rev. 11-94 •
NOTE: Order Q682B Subbase separately.
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 mercury
in a sealed tube, do not place your old control in the trash.
Contact your local waste management authority for in-
structions regarding recycling and the proper disposal of this
control, or of an old control containing mercury in a sealed
If you have questions, call Honeywell Inc. at 1-800-
Check control amperage requirement.
• ©Honeywell Inc. 1994 • Form Number 69-0638—1