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Checking Unit Charge Using Subcooling when
Outdoor Temperature is > 16°C
1 − After the pressures have stabilized, attach the man
ifold gauge hose to the liquid service port, and record
the liquid pressure. At the same time, use a digital ther
mometer to record the liquid line temperature.
2 − Use table 3 to determine the saturation temperature
that corresponds with the liquid line pressure reading.
3 − To determine subcooling, subtract the liquid line tem
perature from the saturation temperature (table 3):
Saturation Temperature
−Liquid Line Temperature
=Subcooling
4 − If the system is operating at subcooling values
higher
than 4.4 − 5.5°C, recover refrigerant.
5 − If the system is operating at subcooling values
lower
than 4.4 − 5.5°C, add refrigerant through the suction
valve in the liquid state.
Some R407C cylinders are
equipped with a dip tube which allows you to draw
liquid refrigerant from the bottom of the cylinder
without turning the cylinder upside−down. The
cylinder will be marked if it is equipped with a dip
tube.
System Operation
The condensing unit and the indoor blower cycle on de
mand from room thermostat. When the thermostat blower
switch is switched to the ON position, the indoor blower op
erates continuously.
TimedOff Control
Units include a timedoff control which helps equalize sys
tem pressures. The timedoff control delays compressor
startup for five minutes on thermostat demand. This allows
the compressor to start in an unloaded condition and pre
vents compressor shortcycling. The control is located in
the control box and is wired between thermostat terminal
Y" and the compressor contactor.
High Pressure and Low Pressure Switches
Units include a high pressure switch and a low pressure
switch. The pressure switches are located on valve cores
in the liquid line to allow for easy access. The manually re
set high pressure switch protects the system from high
pressure conditions which result from a fan failure or a
blocked or dirty coil. The low pressure switch (SPST, NO)
protects the system compressor from damage due to a
loss of charge. The loss of charge switch trips at 25 + 5
psig (172 + 34 kPa) and automatically resets at 55 + 5 psig
(379 + 34 kPa).
Refrigerant Sight Glass
A refrigerant sight glass is provided (in the bag assembly)
with the unit. The sight glass should be fieldinstalled in the
liquid line to monitor the system refrigerant.
Maintenance
WARNING
Electric shock hazard. Can cause inju
ry or death. Before attempting to per
form any service or maintenance, turn
the electrical power to unit OFF at dis
connect switch(es). Unit may have
multiple power supplies.
At the beginning of each cooling season, the system
should be checked as follows:
1 − Clean and inspect condenser coil. Coil may be
flushed with a water hose. Make sure power is off be
fore cleaning.
2 − Visually inspect connecting lines and coils for evidence
of oil leaks.
3 − Check wiring for loose connections.
4 − Check for correct voltage at unit (unit operating).
5 − Check condenser fan motor ampdraw.
Unit nameplate _________ Actual ____________ .
NOTE − If owner complains of insufficient cooling, the unit
should be gauged and refrigerant charge checked. Refer to
section on refrigerant charging in this instruction.
Evaporator Coil
1 − If necessary, clean coil.
2 − Check connecting lines and coils for evidence of oil
leaks.
3 − Check condensate line and clean, if necessary.
Indoor Unit
1 − Clean or change filters.
2 − Adjust blower speed for cooling. The pressure drop
over the coil should be measured to determine the cor
rect blower CFM. Refer to the unit information service
manual for pressure drop tables and procedure.
3 − Belt Drive Blowers Check belt for wear and proper
tension.
4 − Check all wiring for loose connections
5 − Check for correct voltage at unit (blower operating).
6 − Check ampdraw on blower motor
Unit nameplate_________ Actual ____________.
