Checking Compressor Efficiency; Overfeeding - Daikin DCH048 Series Service Instructions Manual

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
machines 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 name-
plates for the correct refrigerant charge.
An inaccurately charged system will cause future prob-
lems.
1. Using a quality set of charging scales, weigh the proper
amount of refrigerant for the system. Allow liquid refrig-
erant 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 refriger-
ant 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 de-
vices that fit into the system charging hose set to accom-
plish this. DO NOT charge liquid R410A into the compres-
sor.
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.
Final Charge Adjustment
The outdoor temperature must be 60°F or higher. Set the
room thermostat to COOL, fan switch to AUTO, and set the
temperature control well below room temperature.
After system has stabilized per startup instructions, com-
pare the operating pressures and outdoor unit amp draw to
the numbers listed in the spec sheet manual. If pressures
and amp draw are too low, add charge. If pressures and amp
draw are too high, remove charge. Check subcooling and
superheat as detailed in the following section.
5. With the system still running, remove hose and reinstall
both valve caps.
6. Check system for leaks.
Due to their design, Scroll compressors are inherently more
tolerant of liquid refrigerant.
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
suction and/or discharge valves, or scroll flanks on Scroll
compressors, reducing the ability of the compressor to pump
refrigerant vapor.
The condition of the valves or 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-
⇒ Below normal high side pressure.
⇒ Above normal low side pressure.
⇒ Low temperature difference across coil.
⇒ Low amp draw at compressor.
-and the charge is correct. The compressor is faulty - replace
the compressor.
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.
During the "OFF" cycle, the high side pressure bleeds to the
low side through the fixed orifice restriction device. Check
equalization time as follows:
1. Attach a gauge manifold to the suction and liquid line dill
valves.
2. Start the system and allow the pressures to stabilize.
3. Stop the system and check the time it takes for the high
and low pressure gauge readings to equalize.
If it takes more than seven (7) minutes to equalize, the
restrictor device is inoperative. Replace, install a liquid line
drier, evacuate and recharge.
S-106 OVERFEEDING
Overfeeding by the expansion valve results in high suction
pressure, cold suction line, and possible liquid slugging of
the compressor.
If these symptoms are observed:
1. Check for an overcharged unit by referring to the cooling
performance charts in the spec sheet manual.
2. Check the operation of the power element in the valve as
explained in S-110 Checking Expansion Valve Opera-
tion.
3. Check for restricted or plugged equalizer tube.
27