Checking External Static Pressure - Daikin DCH048 Series Service Instructions Manual

SERVICING
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 system.
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 Spec 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).
TOTAL EXTERNAL STATIC
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.
If the external static pressure exceeds the minimum or
maximum allowable statics, check for closed dampers, dirty
filters, undersized or poorly laid out ductwork.
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