1F90 and 1F97
FAILURE TO READ AND FOLLOW ALL INSTRUCTIONS CAREFULLY
BEFORE INSTALLING OR OPERATING THIS CONTROL COULD CAUSE
PERSONAL INJURY AND/OR PROPERTY DAMAGE.
voltage, have it inspected by a qualified heating and air
conditioning contractor, electrician, or someone familiar
with basic electricity and wiring.
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 exceed the specification ratings.
All wiring must conform to local and national electrical
codes and ordinances.
Do not short out terminals on gas valve or pri-
burn out thermostat and could cause personal
injury and/or property damage.
WHENTHISTHERMOSTATISCONNECTEDTOSOME If you observe any or all of these conditions after installing
TRONIC MODULES, YOU MAY OBSERVE THE FOL- isolationrelaysbetweenthethermostatandtheelectronic
ignition module. Figures 1 and 2 show how three isolation
relays can be installed [one each for the fan (G), heat (W),
relays to correct the operation conditions.
1. The furnace fan may turn on when heat has not been
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.
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.
Red Jumper Wire
DO NOT REMOVE OR WIRE AROUND LIMIT AND
SAFETY SWITCHES WHEN INSTALLING ISOLA-
Figure 1. Wiring for single transformer systems
EMERSON ELECTRIC CO.
9797 REAVIS ROAD
ST. LOUIS, MISSOURI 63123-5398
PART NO. 37-5426A
Printed in U.S.A.