Cooling Cycle; Operating Your Heat Pump; Heating Cycle; Defrost Cycle - Carrier 38YKC Series Manual To Operating & Maintenance

heat pump supplies air at 85 ° to 90 ° F instead of in sudden
bursts of hot air as with a conventional furnace. The air may
feel cool because it is slightly less than your body tempera-
ture. However, it is sufficiently warm to keep you comfort-
able.
• Ice or frost will tend to form on the outdoor coil during the
winter heating operation. Your heat pump is designed to
automatically melt the ice. When in this defrost cycle, it is
normal for steam or fog to rise from the outdoor unit. Do not
be alarmed!
50 60 70 80
90
50 60 70 80
90
Fig. 2—Manual Changeover Thermostat

OPERATING YOUR HEAT PUMP

The operation of your heat pump system is controlled by the
indoor thermostat. You simply adjust the thermostat and it
maintains the indoor temperature at the level you select.
Most thermostats for heat pump systems have 4 controls:
the temperature control selector, FAN switch, SYSTEM
switch, and EMERGENCY HEAT switch.
The temperature control selector is a dial or lever that
allows you to establish the degree of temperature that you
wish to maintain for your personal comfort. Some thermo-
stats possess 2 temperature control selectors: 1 for setting
the temperature desired during the cooling cycle, and 1 to
set the heating operation temperature. Typical settings are
78 ° F for cooling and 68 ° F for heating.
The FAN switch offers 2 options for controlling the blower:
AUTO and ON. When set to AUTO, the blower will run dur-
ing the time the heat pump is operating. When the FAN
switch is set at the ON position, the blower will run contin-
uously.
Typically, the SYSTEM switch on your thermostat offers
the following selections: COOL, OFF, and HEAT. Your ther-
mostat may also have a fourth selection, AUTO. The heat
pump will not operate when the SYSTEM switch is set at the
OFF position. With the SYSTEM switch set at COOL, your
heat pump will operate in its cooling mode when the indoor
temperature rises above the level that you wish to maintain.
With the SYSTEM switch set at the HEAT position, your
heat pump will provide warmth whenever the indoor tem-
perature falls below the level that you have selected.
The AUTO selection found on some thermostats provides
for automatic changeover between cooling and heating
cycles. With the SYSTEM switch set in the AUTO position,
the cooling mode is activated when the indoor temperature
rises above the thermostat cooling temperature setting, or
the heating mode will be activated when the indoor temper-
ature drops below the thermostat setting for the heating
cycle.
Depending on your typical winter heating needs, your home
comfort system may include a supplementary heating
source. The EMERGENCY HEAT switch provides for con-
venient selection between the 2 heating appliances. Your
heat pump will operate when the switch is set at NORMAL.
With the switch set at the EMERGENCY HEAT position,
the heat pump will turn off and the supplementary heat
source will be activated.
In certain geographic areas and in certain applications, elec-
tric heat is not required. Any questions regarding your
application should be directed to your dealer.
OF F
HE AT
CO OL

COOLING CYCLE

FA N
A U TO
When operating in the cooling cycle, your heat pump will
O N
run until the indoor temperature is lowered to the level you
have selected. On extremely hot days, your conditioner will
EM ER G
run for longer periods at a time and have shorter "off" peri-
ods than on moderate days.
H E A T
The following are typical conditions that add extra heat
and/or humidity to your home. Your cooling unit will work
longer to keep your home comfortable under these condi-
tions:
• 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 are open on the sunny side of the home

HEATING CYCLE

With the SYSTEM switch of your indoor thermostat set to
the HEAT position, the heating section of your home com-
fort 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.
Refer to your furnace User's Manual for specific informa-
tion on heating operation.

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 coil. If allowed
to build up, this ice would impede airflow across the coil and
reduce the amount of heat absorbed from the outside air.
So, to maintain energy-efficient operation, your heat pump
has an automatic defrost cycle.
The defrost cycle starts at a preset time interval of 90 min-
utes, although, it may be reset to either 30 or 50 minutes.
Defrost will start at the preset time only if the ice is sufficient
to interfere with normal heating operation.
After the ice is melted from the outdoor coil, or after a max-
imum of 10 minutes in the defrost mode, the unit will auto-
matically switch back to normal heating operation.
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