13
HEAT PUMPS PAY THEIR
OWN WAY
Heat pump models are available at a nominal
additional cost. In many locales, the payback is
realized in just a few months. Cost and payback
details are provided on the next page.
SPECIAL FEATURES
Two-Stage Thermostat:
The indoor thermostat senses the indoor temperature
and automatically turns on the electric heat to warm
the room quickly. After the desired temperature
conditions
have been satisfied, the thermostat
automatically switches to heat pump mode. If
compressor failure occurs, thethermostat willprovide
backup electric heat automatically.
Outdoor Thermostat:
During the heating cycle, the outdoor thermostat
senses outdoor coil temperature. It switches the unit
to electric heat mode when the outdoor coil
temperature is 28
_
F or below for one minute. The
thermostat switches the unit back to heat pump mode
when the outdoor coil temperature rises above 40
_
F
for ten minutes, which is enough to provide heat to
meet demand. The entire operation is completely
automatic.
Reversing Valve:
The reversing valve provides quiet refrigerant flow
after the unit shuts off. The valve controls the
direction of refrigerant flow for both heating and
cooling functions and remains energized as long as
the controls are in the heat position. When the
cooling controls are activated, the valve automatically
reverses to the cooling position.
Manual Compressor Override Configuration:
This configuration dip switch completely locks out
the compressor. Note that the compressor and heater
do not operate at the same time, thus conserving
energy.
HOW THE HEAT PUMP WORKS
A07553
In Hot Weather:
Carrier’s PTAC units provide indoor comfort in the
same manner as conventional air conditioners,
removing heat and humidity from indoor air. The heat
and humidity is released to the outdoors. Carrier’s
high efficiency design saves energy and reduces
cooling costs.
A07553
In Cool Weather:
When the outdoor coil temperature is above 28
_
F, the
heat pump draws heat from outdoor air and uses it to
heat indoor air. Since heat is transferred and not
produced, Carrier’s heat pump uses less electricity
and reduces energy costs significantly.
A07554
In Sub-Freezing Weather:
When the outdoor coil temperature falls below 28
_
F
for one minute, the unit automatically switches on a
built--in electric heater. The compressor stops and the
indoor fan circulates warm air produced by the heater.
When the outdoor coil temperature rises above 40
_
F
for ten minutes, heat pump operation resumes
automatically.
52M