Heat Pump Operation - Daikin DCC Series Installation Instructions Manual

15. For thermostats with emergency heat switch, return
to step 11. The emergency heat switch is located
at the bottom of the thermostat. Move the switch to
emergency heat. The heat pump will stop, the blower
will continue to run, all heaters will come on and the
thermostat emergency heat light will come on.
16. If checking the unit in the wintertime, when the
outdoor coil is cold enough to actuate the defrost
control, observe at least one defrost cycle to make
sure the unit defrosts completely.
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. See Sections on
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 Appendix B. RLA draw can be much lower than values
listed at low load conditions and low ambient condensing tem-
peratures. Values 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 "condenser" becomes "evaporator", "evaporator"
becomes "condenser", "cooling" becomes "heating".
H C
eating yCle
The heat pump operates in the heating cycle by redirecting
refrigerant flow through the refrigerant circuit external to the
compressor. This is accomplished with through the reversing
valve. Hot discharge 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 (con-
denser 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.
C
HeCk
The following figures show a schematic of a heat pump on the
cooling 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 reverse of refrigerant flow.
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 difference in the outdoor temperature and the
outdoor coil temperature, the greater the heating capacity of
the heat pump. This phenomenon is a characteristic of a heat
pump. It is a good practice to provide supplementary heat
for all heat pump installations in areas where the tempera-
ture 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.
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