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SERVICING
Only use refrigerant certified to AHRI standards. Used
refrigerant may cause compressor damage. Daikin is not
responsible for damage or the need for repairs resulting
from the use of unapproved refrigerant types or used or
recycled refrigerant. Most portable machinces cannot
clean used refrigerant to meet AHRI standards.
Operating the compressor with the suction valve closed
will cause serious compressor damage.
Charge the system with the exact amount of refrigerant.
Refer to the specification section or check the unit
nameplates for the correct refrigerant charge.
An inaccurately charged system will cause future
problems.
1. Using a quality set of charging scales, weigh the
proper amount of refrigerant for the system. Allow
liquid refrigerant only to enter the high side.
2. After the system will take all it will take, close the
valve on the high side of the charging manifold.
3. Start the system and charge the balance of the
refrigerant through the low side.
NOTE: R410A should be drawn out of the storage
container or drum in liquid form due to its fractionation
properties, but should be "Flashed" to its gas state before
entering the system. There are commercially available
restriction devices that fit into the system charging hose
set to accomplish this. DO NOT charge liquid R410A into
the compressor.
4. With the system still running, close the valve on the
charging cylinder. At this time, you may still have
some liquid refrigerant in the charging cylinder hose
and will definitely have liquid in the liquid hose.
Reseat the liquid line core. Slowly open the high side
manifold valve and transfer the liquid refrigerant from
the liquid line hose and charging cylinder hose into
the suction service valve port. CAREFUL: Watch so
that liquid refrigerant does not enter the compressor.
Due to their design, Scroll compressors are inherently
more tolerant of liquid refrigerant.
22
CAUTION
CAUTION
NOTE: Even though the compressor section of a scroll
compressor is more tolerant of liquid refrigerant,
continued floodback or flooded start conditions may
wash oil from the bearing surfaces causing premature
bearing failure.
S-104 Checking Compressor Efficiency
The reason for compressor inefficiency is broken or
damaged scroll flanks on Scroll compressors, reducing the
ability of the compressor to pump refrigerant vapor.
The condition of the scroll flanks is checked in the
following manner.
1. Attach gauges to the high and low side of the system.
2. Start the system and run a "Cooling Performance Test.
If the test shows:
A.
Below normal high side pressure.
B.
Above normal low side pressure.
C.
Low temperature difference across coil.
D.
Low amp draw at compressor.
And the charge is correct. The compressor is faulty -
replace the compressor.
S-105 Thermostatic Expansion Valve
The expansion valve is designed to control the rate of
liquid refrigerant flow into an evaporator coil in exact
proportion to the rate of evaporation of the refrigerant
in the coil. The amount of refrigerant entering the coil is
regulated since the valve responds to temperature of the
refrigerant gas leaving the coil (feeler bulb contact) and the
pressure of the refrigerant in the coil.
This regulation of the flow prevents the return of liquid
refrigerant to the compressor.
The three forces which govern the operation of the valve
are: (1) the pressure created in the power assembly by the
feeler bulb, (2) evaporator pressure, and (3) the equivalent
pressure of the superheat spring in the valve.
0% bleed type expansion valves are used on the indoor
coils. The 0% valve will not allow the system pressures
(High and Low side) to equalize during the shut down
period. The valve will shut off completely at approximately
100 PSIG Pressure.
Good thermal contact between the feeler bulb and the
suction line is essential to satisfactory valve control and
performance.
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