Compressor Burnout; Checking External Static Pressure; Checking Belt Tension - Daikin DCH048 Series Service Instructions Manual

SERVICING
S-115 COMPRESSOR BURNOUT
When a compressor burns out, high temperature develops
causing the refrigerant, oil and motor insulation to decom-
pose forming acids and sludge.
If a compressor is suspected of being burned-out, attach a
refrigerant hose to the liquid line dill valve and properly remove
and dispose of the refrigerant.
Now determine if a burn out has actually occurred. Confirm
by analyzing an oil sample using a Sporlan Acid Test Kit, AK-
3 or its equivalent.
Remove the compressor and obtain an oil sample from the
suction stub. If the oil is not acidic, either a burnout has not
occurred or the burnout is so mild that a complete clean-up
is not necessary.
If acid level is unacceptable, the system must be cleaned by
using the clean-up drier method.
CAUTION
Do not allow the sludge or oil to contact the skin.
Severe burns may result.
NOTE: Daikin does NOT approve the flushing method using
R-11 refrigerant.
Suction Line Drier Clean-Up Method
The POE oils used with R410A refrigerant is an excellent
solvent. In the case of a burnout, the POE oils will remove any
burnout residue left in the system. If not captured by the
refrigerant filter, they will collect in the compressor or other
system components, causing a failure of the replacement
compressor and/or spread contaminants throughout the
system, damaging additional components.
Use part number RF000127 suction line filter drier kit. This
drier should be installed as close to the compressor suction
fitting as possible. The filter must be accessible and be
rechecked for a pressure drop after the system has operated
for a time. It may be necessary to use new tubing and form
as required.
NOTE: At least twelve (12) inches of the suction line
immediately out of the compressor stub must be discarded
due to burned residue and contaminates.
1. Remove the liquid line drier and expansion valve.
2. Purge all remaining components with dry nitrogen or
carbon dioxide until clean.
3 Install new components including liquid line drier.
4. Braze all joints, leak test, evacuate, and recharge sys-
tem.
5. Start up the unit and record the pressure drop across the
drier.
6. Continue to run the system for a minimum of twelve (12)
hours and recheck the pressure drop across the drier.
Pressure drop should not exceed 6 PSIG.
7. Continue to run the system for several days, repeatedly
checking pressure drop across the suction line drier. If
the pressure drop never exceeds the 6 PSIG, the drier has
trapped the contaminants. Remove the suction line drier
from the system.
8. If the pressure drop becomes greater, then it must be
replaced and steps 5 through 9 repeated until it does not
exceed 6 PSIG.
NOTICE: Regardless, the cause for burnout must be deter-
mined and corrected before the new compressor is started.
S-200 CHECKING EXTERNAL STATIC
PRESSURE
The minimum and maximum allowable duct static pressure
is found in the Specification Sheet Manual.
Too great of an external static pressure will result in insuffi-
cient air that can cause icing of the coil, whereas too much
air can cause poor humidity control, and condensate to be
pulled off the evaporator coil causing condensate leakage.
Too much air can cause motor overloading and in many cases
this constitutes a poorly designed system. To determine
proper air movement, proceed as follows:
1. Using a draft gauge (inclined manometer) measure the
static pressure of the return duct at the inlet of the unit,
(Negative Pressure).
2. Measure the static pressure of the supply duct, (Positive
Pressure).
3. Add the two readings together.
NOTE: Both readings may be taken simultaneously and read
directly on the manometer if so desired.
4. Consult proper table for quantity of air.
S-205 CHECKING BELT TENSION
NOTE: Section on high static tables may require a field motor
change.
BELT DRIVE
T A A
ENSION AND LIGNMENT
Check drive for adequate run-in belt tension. Correct belt
tension is very important. A belt that is loose will have a
substantially shorter life, and a belt that is too tight may
cause premature motor and bearing failure. Correct belt
tension on these units can be checked by measuring the
force required to deflect the belt 1/8" at the midpoint of the
span length (Figure 21). Belt tension force can be measured
using a belt tension checker, available through most belt
manufacturers. The correct deflection force is 5 Ibs. for a new
belt and 3.5 Ibs. for a belt that has been run in. New belt
tension includes initial belt stretch. When new V-belts are
installed on a drive the initial tension will drop rapidly during
the first few hours. Check tension frequently during the first
24 hours of operation. Subsequent retensioning should fall
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