Checking External Static Pressure; Adjusting Airflow; Checking Temperature Rise - Daikin M Series Service And Troubleshooting

SERVICING
heat to the valve body when brazing the line connection.
The use of a wet rag sometimes can be a nuisance. There
are commercial grades of heat absorbing paste that may
be substituted.
After the valve has been installed, leak test, evacuate and
recharge.

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.

Adjusting Airflow

The A/GPDM3 models are equipped with EEM motors.
EEM motors are constant torque motors with very low
power consumption. This motor is energized by 24VAC.
Adjust the CFM for the unit by changing the 24VAC leads
to the speed terminal block on the motor.
NOTE: Heating airflow must be adjusted to provide the
temperature rise shown on rating plate. A higher speed
tap may not provide more airflow. Blower speeds
are programmed to deliver adequate airflow at rated
external static pressure (ESP).
Multi-speed ECM is controlled by three 24V low voltage
leads:
T1, T2, and T4.
T1 - Low speed Heating
T2 - High speed Heating
T3 - Low Speed Cooling (optional)
T4 - Medium speed Cooling
T5 - High Speed Cooling (optional)
NOTE: To adjust the blower to high speed, move T4 to
T5 in cooling operation

Checking Temperature Rise

Temperature rise is related to the BTUH output of the unit
and the amount of air (CFM) circulated over the indoor coil.
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.
4. Take motor amperage draw to determine that the
motor is not overloaded during adjustments.
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