Heat Pump Operation - Daikin DCC Series Installation Instructions Manual

F S C
INAL YSTEM HECKS
1. Check to see if all supply and return air grilles are adjusted
and the air distribution system is balanced for the best
compromise between heating and cooling.
2. Check for air leaks in the ductwork.
Air Flow Adjustments.
3. Make sure the unit is free of "rattles", and the tubing in
the unit is free from excessive vibration. Also make sure
tubes or lines are not rubbing against each other or sheet
metal surfaces or edges. If so, correct the trouble.
4. Set the thermostat at the appropriate setting for cooling
and heating or automatic change over for normal use.
5. Be sure the Owner is instructed on the unit operation, filter,
servicing, correct thermostat operation, etc.
R P
EFRIGERATION ERFORMANCE
Check that compressor RLA corresponds to values shown in Ap-
pendix B. RLA draw can be much lower than values listed at low
load conditions and low ambient condensing temperatures. Val-
ues in Appendix B can slightly exceed at high load conditions and
high ambient condensing temperatures.

HEAT PUMP OPERATION

C C
OOLING YCLE
When the heat pump is in the cooling cycle, it operates exactly as
a Summer Air Conditioner unit. In this mode, all the charts and
data for service that apply to summer air conditioning apply to the
heat pump. Most apply on the heating cycle except that "con-
denser" becomes "evaporator", "evaporator" becomes "con-
denser", "cooling" becomes "heating".
H C
EATING YCLE
The heat pump operates in the heating cycle by redirecting refrig-
erant flow through the refrigerant circuit external to the compres-
sor. This is accomplished with through the reversing valve. Hot dis-
charge vapor from the compressor is directed to the indoor coil
(evaporator on the cooling cycle) where the heat is removed, and
the vapor condenses to liquid. It then goes through the expansion
device to the outdoor coil (condenser on the cooling cycle) where
the liquid is evaporated, and the vapor goes to the compressor.
When the solenoid valve coil is operated either from heating to
cooling or vice versa, the piston in the reversing valve to the low
pressure (high pressure) reverse positions in the reversing valve.
The following figures show a schematic of a heat pump on the cool-
ing cycle and the heating cycle. In addition to a reversing valve, a
heat pump is equipped with an expansion device and check valve
for the indoor coil, and similar equipment for the outdoor coil. It is
also provided with a defrost control system.
The expansion devices are flowrator distributors and perform the
same function on the heating cycle as on the cooling cycle. The
flowrator distributors also act as check valves to allow for the re-
verse of refrigerant flow.
See Sections on
C
HECK
When the heat pump is on the heating cycle, the outdoor coil is
functioning as an evaporator. The temperature of the refrigerant
in the outdoor coil must be below the temperature of the outdoor
air in order to extract heat from the air. Thus, the greater the dif-
ference in the outdoor temperature and the outdoor coil tempera-
ture, the greater the heating capacity of the heat pump. This phe-
nomenon is a characteristic of a heat pump. It is a good practice to
provide supplementary heat for all heat pump installations in ar-
eas where the temperature drops below 45° F. It is also a good
practice to provide sufficient supplementary heat to handle the
entire heating requirement should there be a component failure
of the heat pump, such as a compressor, or refrigerant leak, etc.
Since the temperature of the refrigerant in the outdoor coil on the
heating cycle is generally below freezing point, frost forms on the
surfaces of the outdoor coil under certain weather conditions of
temperature and relative humidity. Therefore, it is necessary to
reverse the flow of the refrigerant to provide hot gas in the out-
door coil to melt the frost accumulation. This is accomplished by
reversing the heat pump to the cooling cycle. At the same time,
the outdoor fan stops to hasten the temperature rise of the out-
door coil and lessen the time required for defrosting. The indoor
blower continues to run and the supplementary heaters are ener-
gized.
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