S-200 Checking External Static Pressure - Daikin DP14UM Service Instructions Manual

SERVICING
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.
Do not allow the sludge or oil to contact the skin.
Severe burns may result.
NOTE: The Flushing Method using R-11 refrigerant is no
longer approved by Daikin Brand Heating-Cooling.
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.
The suction line filter 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 compressor discharge line strainer.
2. Remove the liquid line drier and expansion valve.
3. Purge all remaining components with dry nitrogen or
carbon dioxide until clean.
4. Install new components including liquid line drier.
5. Braze all joints, leak test, evacuate, and recharge
system.
6. Start up the unit and record the pressure drop across
the drier.
7. 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.
8. 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.
26
CAUTION
9. 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
determined 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 Technical Information Manual.
Too great of an external static pressure will result in
insufficient 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 digital 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.