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506318-03CPage 6 of 11 mrcool.com
Start-Up Procedure
1. Check to ensure:
• Service valve and gage port caps are installed and
tightened.
• Voltage supply at unit agrees with nameplate rating.
• Field wiring connections are tight and factory wiring
has not been disturbed and are tight.
• Indoor fan motor is on correct speed tap.
2. Set thermostat selector switch to OFF and fan control
switch to “Auto” is so equipped.
3. Close electrical disconnects to energize system.
4. Set room thermostat at desired temperature. Be sure
set point is below indoor ambient temperature.
5. Set the system switch of the thermostat on COOL
(or HEAT if applicable) and fan switch for continuous
operation (ON) or AUTO, as desired. There will be
a 5 minute short cycle compressor delay on startup.
Operate unit for 15-20 minutes, then check the system
refrigerant charge.
6. Adjust refrigerant charge per “Adjusting Charge”
section.
Adjusting Charge
Factory charge is shown on the rating label located on the
access panel.
All split system heat pumps are factory charged for 15
feet of connecting line set and matched indoor fan coil.
Nameplate refrigerant charge should initially be adjusted
for line set lengths other than 15 feet. For line sets shorter
than 15 feet in length, remove charge. For line sets longer
lengths.
Refrigeration Charge Adjustment
Liquid Line Diameter Oz. Per Linear Foot
3/8” 0.6
* Factory charge for series is for 15’ (ft.) line sets and
matched fan coil.
Table 2.
Blower charts are calculated with a dry or wet coil basis.
Btuh) through a wet coil. Refer to indoor unit instructions for
The optimum method for checking the charge is by
weight. However the following methods may be used
Cooling Mode
1. Operate unit a minimum of 10 minutes before checking
charge.
2. Measure liquid service valve pressure by attaching an
accurate gage to service port. Determine saturation
temp. from T/P chart.
3. Measure liquid line temperature by attaching an
accurate thermistor type or electronic thermometer to
liquid line near outdoor coil.
4. Calculate subcooling (saturation temp. measured
temp.) and compare with table on back of central box
cover.
5. Add refrigerant if subcooling is lower than table.
Recover refrigerant if subcooling is high.
6. If ambient temp is lower than 60°F, check charge in
heating mode or weigh refrigerant according to name
plate data.
Heating Mode
Check charge in heating mode if ambient temp is below
60° F. Indoor temp must be between 65° and 75° F.
Follow steps (1) to (6) above and compare with heating
mode subcooling range on the table on back of central box
cover.
Charge must be rechecked again during the cooling
season.
Cold Weather Application
A cold weather accessory kit may be required for heat
pumps operating at ambient conditions below 25°F.
Supplemental heat should be provided for these conditions
due to the expected performance degeneration.
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