Checking Temperature Rise - Daikin DCH048 Series Service Instructions Manual

SERVICING
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 PRES-
SURE
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
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 draft gauge (inclined manometer) measure the
static pressure of the return duct at the inlet of the unit,
(Negative Pressure).
36
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.
S-201 CHECKING TEMPERATURE RISE
Temperature rise is related to the BTUH output of the unit and
the amount of air (CFM) circulated over the heat exchanger.
All units are designed for a given range of temperature
increase. This is the temperature of the air leaving the unit
minus the temperature of the air entering the unit.
The more air (CFM) being delivered through a given unit the
less the rise will be; so the less air (CFM) being delivered, the
greater the rise. The temperature rise should be adjusted in
accordance to a given unit specifications and its external
static pressure.
1. Check BTUH input to unit do not exceed input rating
stamped on rating plate.
2. Take entering and leaving air temperatures.
3. Select the proper speed tap or dip switch setting for direct
drive units.