Daikin DP5HH2441 Series, Руководство по установке

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Figure 7 shows 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 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 liquid 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 outdoor 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 outdoor coil and lessen the time required for
defrosting. The indoor blower continues to run and the
supplementary heaters are energized.
DEFROST CONTROL
During operation the power to the circuit board is controlled
by a temperature sensor, which is clamped to a feeder tube
entering the outdoor coil. Defrost timing periods of 30,60
and 90 minutes may be selected by setting the circuit
board jumper to 30, 60 and 90 respectively. Accumulation
of time for the timing period selected starts when the
sensor closes (approximately 30 ± 5°F), and when the wall
thermostat calls for heat. At the end of the timing period,
the unit’s defrost cycle will be initiated provided the sensor
remains closed. When the sensor opens (approximately 60
± 5°F), the defrost cycle is terminated and the timing period
is reset. If the defrost cycle is not terminated due to the
sensor temperature, a twelve minute override interrupts the
unit’s defrost period.
SUGGESTED FIELD TESTING/
TROUBLESHOOTING
1. Run unit in the heating mode (room thermostat
calling for heat).
2. Check unit for proper charge. Note: Bands of frost on
the condenser coil indicate low refrigerant charge.
3. Shut off power to unit.
4. Disconnect outdoor fan by removing the outdoor fan
motor wire from “DF2” on defrost control.
5. Restart unit and allow frost to accumulate.
6. After a few minutes of operation, the unit’s defrost
thermostat should close. To verify this, check for
24 volts between “DFT” and “C” on board. If the
temperature at the thermostat is less than 28°F and
the thermostat is open, replace the unit’s defrost
thermostat, as it is defective.
7. When the unit’s defrost thermostat has closed, short
the test pins on the defrost board until the reversing
valve shifts, indicating defrost. This should take up
to 22 seconds depending on what timing period the
control is set on. After defrost initiation, the short
must instantly be removed or the unit’s defrost period
will only last 3 seconds.
8. The control is shipped from the factory with the
compressor delay option selected. This will de-
energize the compressor contactor for 30 seconds
on defrost initiation and defrost termination. If
the jumper is set to Normal, the compressor will
continue to run during defrost initiation and defrost
termination. The control will also ignore the low
pressure switch connected to R-PS1 and PS2 for 5
minutes upon defrost initiation and 5 minutes after
defrost termination.
9. After the unit’s defrost thermostat has terminated,
check the defrost thermostat for 24 volts between
“DFT” and “C”. The reading should indicate 0 volts
(open sensor).
10. Shut off power to unit.
11. Replace outdoor fan motor lead to terminal “DF2” on
defrost board and turn on power.
AIR FLOW MEASUREMENT
AND ADJUSTMENT
After reviewing section on DUCTING, proceed with airflow
measurements and adjustments. Unit’s blower curves
(in Specification Sheets) are based on external static
pressure (ESP, in. of W.C.). The duct openings on the unit
are considered internal static pressure, so as long as ESP
is maintained, the unit will deliver the proper air up to the
maximum static pressure listed for the CFM required by the
application (i.e. home, building, etc.).