Optimizing System Refrigerant Charge - Lennox Merit 13HPX Series Installation Instructions Manual

CHECK / EXPANSION
BI−FLOW FILTER / DRIER
NOTE − Use gauge ports on vapor line valve and liquid valve for evacuating refrigerant lines and
indoor coil. Use true suction port to measure vapor pressure during charging.

Optimizing System Refrigerant Charge

This section provides instructions on optimizing the
system charge. This section includes:
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Optimizing procedure
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Adjusting indoor airflow
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Using subcooling method
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Approved matched components, targeted subcooling
(SC) values and add charge values
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Normal operating pressures
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Temperature pressures
OPTIMIZING PROCEDURE
1. Move the low−side manifold gauge hose from the
vapor line service valve to the true suction port (see
figure 19).
2. Set the thermostat for either cooling or heating
demand. Turn on power to the indoor unit and close
the outdoor unit disconnect switch to start the unit.
3. Allow unit to run for five minutes to allow pressures to
stabilize.
4. Check the airflow as instructed under Adjusting Indoor
Airflow to verify or adjust indoor airflow for maximum
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OUTDOOR UNIT
VALVE
MUFFLER
LIQUID LINE
SERVICE PORT
Figure 21. Heat Pump Cooling Cycle
search engine
DISTRIBUTOR
REVERSING VALVE
OUTDOOR
COIL
TRUE SUCTION
PORT
COMPRESSOR
efficiency. Make any air flow adjustments before
continuing with the optimizing procedure.
5. Use subcooling method to optimize the system
charge (see figure 23). Adjust charge as necessary.
ADJUSTING INDOOR AIRFLOW
Heating Mode Indoor Airflow Check
(Only use when indoor unit has electric heat)
Indoor blower airflow (CFM) may be calculated by
energizing electric heat and measuring:
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Temperature rise between the return air and supply air
temperatures at the indoor coil blower unit,
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Measuring voltage supplied to the unit,
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Measuring amperage being drawn by the heat unit(s).
Then, apply the measurements taken in the following
formula to determine CFM:
Amps x Volts x 3.41
CFM =
1.08 x Temperature rise (F)
Cooling Mode Indoor Airflow Check
Check airflow using the Delta−T (
22.
Page 25
NOTE − ARROWS INDICATE DIRECTION
OF REFRIGERANT FLOW
INDOOR UNIT
VAPOR
SERVICE
PORT
CHECK / EXPANSION VALVE
DT)
process using figure
INDOOR
COIL
13HPX SERIES