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PART NO. 37-5426A
9507
1F90 and 1F97
Addendum to
INSTALLATION INSTRUCTIONS
WHITE-RODGERS
R
WHITE-RODGERS DIVISION
EMERSON ELECTRIC CO.
9797 REAVIS ROAD
ST. LOUIS, MISSOURI 63123-5398
FAILURE TO READ AND FOLLOW ALL INSTRUCTIONS CAREFULLY
BEFORE INSTALLING OR OPERATING THIS CONTROL COULD CAUSE
PERSONAL INJURY AND/OR PROPERTY DAMAGE.
PRECAUTIONS
If in doubt about whether your wiring is millivolt, line, or low
voltage, have it inspected by a qualified heating and air
conditioning contractor, electrician, or someone familiar
with basic electricity and wiring.
Do not exceed the specification ratings.
All wiring must conform to local and national electrical
codes and ordinances.
To prevent electrical shock and/or equipment
damage, disconnect electric power to system, at
main fuse or circuit breaker box, until installa-
tion is complete.
Do not short out terminals on gas valve or pri-
mary control to test. Short or incorrect wiring will
burn out thermostat and could cause personal
injury and/or property damage.
CAUTION
!
INSTALLATION
WHEN THIS THERMOSTAT IS CONNECTED TO SOME
SYSTEMS THAT USE HIGH IMPEDANCE INPUT ELEC-
TRONIC MODULES, YOU MAY OBSERVE THE FOL-
LOWING CONDITIONS.
1. The furnace fan may turn on when heat has not been
called, or may not turn off when thermostat is satisfied
and call for heat ends.
2. The furnace may not turn off when thermostat is
satisfied and call for heat ends.
3. The air conditioner may not turn off when thermostat
is satisfied and call for cool ends.
If you observe any or all of these conditions after installing
thermostat, you can correct system operation by installing
isolation relays between the thermostat and the electronic
ignition module. Figures 1 and 2 show how three isolation
relays can be installed [one each for the fan (G), heat (W),
and cool (Y)]. You may not need to install all three isolation
relays to correct the operation conditions.
Transformer
Red Jumper Wire
THERMOSTAT
24 VAC
Line
Voltage
Figure 1. Wiring for single transformer systems
RH W Y G RC
Heating
System
Cooling
System
Fan
Relay
Figure 1 shows a single transformer heating/cooling sys-
tem, with isolation relays installed in the heating (W),
cooling (Y), and fan (G) circuits. To simplify the diagram,
limit and safety switches are not shown here, although
they will be found either in the low or high voltage circuit.
Limit and safety switches must be retained. Refer to the
equipment manufacturer’s system wiring diagram for the
location of limit and safety switches.
DO NOT REMOVE OR WIRE AROUND LIMIT AND
SAFETY SWITCHES WHEN INSTALLING ISOLA-
TION RELAYS.
WARNING
!