17
System Control
The SYSTEM or MODE control on your thermostat offers the following selections: COOL, OFF, HEAT, and EM HEAT. Neither
the cooling nor heating equipment will operate when the SYSTEM or MODE control is set to OFF. With the SYSTEM or MODE
control set to COOL, your unit will operate in cooling mode. With the SYSTEM or MODE control set to HEAT, your unit will
operate in heating mode.
Auxiliary Heating
Your system also includes an auxiliary electric heating source. The SYSTEM or MODE control options HEAT and EM HEAT
provide convenient selection between the two heating appliances. The heat pump will operate when SYSTEM or MODE control
is set to HEAT. The auxiliary electric heater may also be used on cold days to supplement heat pump heating. With the
SYSTEM or MODE control set to EM HEAT, the heat pump is turned off and the auxiliary electric heat is activated. The unit
is now operating as an electric furnace.
On heat pump systems, the wall thermostat regulates the use of auxiliary electric heat to maximize energy efficiency and
your home comfort.
COOLING CYCLE
When operating in the cooling cycle, your unit will operate until the indoor temperature is lowered to the level you have selected
on the indoor thermostat. On extremely hot days, your unit will operate for longer periods of time and have shorter “off” periods
than on moderate days.
The following are typical conditions that add extra heat and/or humidity to your home and force your cooling unit to work longer
to keep your home comfortable:
•
Entrance doors are frequently opened and closed.
•
Laundry appliances are being operated.
•
A shower is running.
•
More than the usual number of people are present in the home.
•
More than the normal number of electric lights are in use.
•
Drapes or blinds are open on the sunny side of the building or home.
HEATING CYCLE
With the SYSTEM control of your indoor thermostat set to HEAT, the heating section of your home comfort system will operate
until room temperature is raised to the level you have selected. Of course, the heating unit will have to operate for longer periods
to maintain a comfortable environment on cooler days and nights than on moderate ones. When the demand is greater than
the capacity of the heat pump alone, the auxiliary electric heaters will supplement the heat pump.
DEFROST CYCLE
When your heat pump is providing heat to your home and the outdoor temperature drops below 45°F, moisture may begin
to freeze on the surface of the outdoor-air coil. If allowed to build up, this ice would impede airflow across the coil and reduce
the amount of heat absorbed from outside air. To maintain energy-efficient operation, your heat pump has an automatic defrost
cycle.
The defrost cycle will occur only if ice is sufficient to interfere with normal heating operation. After ice is melted from the outdoor-
air coil, the unit automatically switches back to normal heating mode.
Do not be alarmed if steam or fog appears at the outdoor-air exhaust during the defrost cycle. Water vapor from the melting
ice may condense into a mist in the cold outdoor air.
NOTE: Non-Heat Pump models use a single stage heat thermostat. When a demand for heat is made,
these units will use the electric heat strip heat immediately.
