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Installation
Fine Tuning The System Charge
Once the initial charge is completed, additional refrigerant
will need to be added with the unit running.
Important:
An adequate heat load must be supplied to
ensure a proper charge.
1. Disconnect the refrigerant cylinder from the discharge
side of the compressor and connect it to the suction
side.
2. Start the A/C system and use the system controller to
lower the room temperature setpoint 3-5°F below
actual room temperature, thus ensuring cooling
remains on as the unit is charged.
When fine tuning the charge on cool days it will be
necessary to restrict the airflow across the condenser
coil to raise the pressure. The fan closest to the header
must be running. When fine tuning the charge, ensure
the pressures are correct for the type of refrigerant
used. Refer to the tables in
Procedures," p. 27
for the operating temperatures and
pressures for the type of refrigerant used in your
system.
0ºF Fan Cycling and -20ºF Variable Speed Control
The following instructions are for charging systems with
condenser fan cycling or variable fan speed control using
R407C refrigerant.
1. Partially block the airflow to the condenser with
cardboard to raise the discharge pressure. Allow the
discharge pressure to rise high enough to start the first
fan only, then maintain a constant pressure. This will
lower the possibility of overcharging.
a. R407C Refrigerant- Allow the discharge pressure to
rise to 260-315 psig and hold it constant.
2. Slowly meter liquid refrigerant through the suction
side while watching the pressure gauges and
monitoring superheat and sub-cooling temperatures.
Important:
Add liquid refrigerant slowly to prevent the
refrigerant oil from "washing out" of the
compressor.
3. Take a superheat temperature reading near the feeler
bulb from the thermal expansion valve with the
temperature measuring device being well insulated.
The ideal amount of superheat is 10-15°F. Maximum
allowable amount of superheat is 20°F.
4. While monitoring the pressure, take a sub-cooling
temperature reading on the output side of the con-
denser. The amount of sub-cooling should be 10-20°F.
5. If necessary, (slowly) add liquid refrigerant to the
suction side to achieve the sub-cooling temperature.
6. If the unit has hot gas reheat (optional), the previous
steps are still followed except the hot gas reheat valve
must be open to allow refrigerant to flow into the
reheat coil to obtain the proper amount of refrigerant
charge. This can be done using the system controller to
30
"System Charging
enable a call for dehumidification (lower the humidity
setpoint). This process may need to be repeated
several times. After cycling the system through the hot
gas reheat cycle, recheck the system charge with the
system only in the cooling mode.
Important:
Remove the blockage to the air intake of the
condenser.
7. Fill out the applicable sections of Warranty
Registration and Start-up Checklist.
30°F Flooded Head Pressure Control
Notes:
•
For units using flooded head pressure control, a
receiver is used to store the refrigerant during the time
the condenser is not utilizing the extra refrigerant
charge
•
It is important not to exceed 80% of the total condenser
and receiver volume to allow room for expansion.
1. Fine tune the charge following steps 1-6 in Section
Fan Cycling and -20ºF Variable Speed Control," p.
2. The head pressure control valve setting is printed on
the side of the valve body. This setting is the lowest
head pressure that will be maintained during system
operation. It may be necessary to add additional
refrigerant to raise the head pressure to the value
printed on the valve (225 psig for R407C).
3. If a refrigerant level sight glass is included on the side
of the receiver, it may be used to assist in charging the
air conditioning system. The proper charge can be
confirmed by viewing the level of refrigerant in the
receiver(s) while the unit is running at an elevated
discharge pressure.
4. Add additional refrigerant charge until the refrigerant
level in the receiver rises to the center of the sight
glass, indicating the receiver is 80% filled.
5. When the refrigerant in the receiver reaches the center
of the sight glass, the unit is fully charged.
Important:
Remove the blockage to the air intake of the
condenser.
6. Fill out the applicable sections of Warranty
Registration and Start-Up Checklist.
Refrigerant Characteristics
Pressure/Temperature Settings
The following table is provided to assist with the normal
settings of the system for R407C refrigerant. Where
applicable, minimum and maximum settings are given
along with normal operating pressures.
"0ºF
30.
AH-SVX008C-EN
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