13
NOTE: Never run CFM below 300 CFM per ton,
evaporator freezing or poor unit performance is
possible.
Total External Static Pressure
1.
Using a digital manometer measure the static
pressure of the return duct at the inlet of the unit
(Negative Pressure). See Figure 12 - Total External
Static.
Mode
.
Total External Static
Figure 12
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
filter, undersized or poorly laid out ductwork.
AIR FLOW ADJUSTMENTS FOR INDOOR
BLOWER MOTOR
ECM Motor
The ECM control board is factory set with the dip switch
#4 in the “ON” position for single stage units and to the
“OFF” position for the two-stage units. The remaining dip
switches shall be verified and adjusted during installation to
the tap settings as shown in the airflow table-see Appendix.
For most applications, the settings are to be changed
according to the electric heat size.
The ECM motor provides many features not available on
the traditional PSC motor. These features include:
•
Improved Efficiency
•
Constant CFM
•
Soft Start and Stop
•
Improved Humidity Control
ECM Motor Speed Adjustment
Each ECM blower motor has been preprogrammed for
operation at 4 distinct air flow levels when operating in
Cooling/Heat Pump mode or Electric Heat mode. These 4
distinct levels may also be adjusted slightly lower or higher
if desired. The adjustment between levels and the trim
adjustments are made by changing the dip switch(s) either
to an “OFF” or “ON” position.
See Appendix for Blower Performance Data tables.
DP5HM DIP Switch Functions
The ECM motor has an electronic control that contains
eight (8) 2-position dip switches. The function of these
dip switches is shown below. See Figure 13 - DIP Switch
Function.
DIP SWITCH NUMBER
FUNCTION
1
2
3
N/A
4
Indoor Thermostat
5
6
7
8
Cooling & Heat Pump CFM
CFM Trim Adjust
Electric Heat
DIP Switch Function
Figure 13
DP5HM CFM Delivery and Adjustments
See Appendix for CFM Output, Adjustments and DIP switch
settings.
DP5HM Thermostat “Fan Only” Mode
During Fan Only Operations, the CFM output is 50% of the
high stage cooling setting.
DP5HM Humidity Control
When using a Humidistat (normally closed), cut jumper PJ6
on the control board. The Humidistat will only affect both
low stage and high stage cooling air flow by adjusting the
Air flow to 85%.
SUPERHEAT AND SUBCOOLING
Checking Subcooling
NOTE: Units with a TXV should be charged to
Subcooling only.
Example:
a. Liquid Line Pressure = 417 PSI
b. Corresponding Temp. = 120°F
c. Thermometer on Liquid line = 109°F
To obtain the amount of subcooling, subtract 109°F
from 120°F. The difference is 11° subcooling. See the
specification sheet or technical information manual for the
design subcooling range for your unit.
