Instructions / Assembly

ENGLISH

About Dual Fuel Heat Pump Systems

A dual fuel heat pump typically has a gas furnace combined with a heat pump. The gas furnace is used

as auxiliary heat unless the outdoor temperature is very low, in which case it is used as the primary

heat source.

1. When used with dual fuel heat pumps, the EER56000 thermostat requires a method for obtaining the

outdoor temperature. A Wiser Thermostat External Temperature sensor (EER57200) can be

physically connected to the “Remote Temp. Sensor” terminals on the thermostat, or the EER56000

thermostat can obtain the outdoor temperature from a remote system.

If the EER56000 thermostat cannot obtain the outdoor temperature, the heat pump compressor

will not operate and the thermostat will only call for the auxiliary heat until the problem is resolved.

When this occurs, the display will flash red and the “Problem With Outdoor Temperature Sensor.

Some Heat Stages May Be Disabled” error message will be displayed. After the error has been

acknowledged, “Outdoor Sensor Fault” will be displayed in the Message Bar until the problem is

resolved.

2. Balance Setpoint Limits:

— If the outdoor temperature is above the “Upper Balance Setpoint” (45 °F by default), the heat

pump is used exclusively.

— If the outdoor temperature falls below the “Upper Balance Setpoint” but is above the “Lower

Balance Setpoint” (35 °F by default), and if the heat pump is unable to heat at a rate of 5

degrees per hour or better, the heat pump will turn off and auxiliary heat will be used until the

call for heat has been satisfied.

— If the outdoor temperature falls below the “Lower Balance Setpoint”, the heat pump will turn off

and the auxiliary heat will be used until the call for heat has been satisfied.

— The Balance Setpoint Limits can be adjusted according to the manufacturer's specifications.

3. When the EER56000 thermostat makes a call for auxiliary heat, the heat pump compressor is

turned off and the auxiliary heat is used exclusively.