CyberOne EC DX IOM Manual
FINE TUNING THE SYSTEM CHARGE
1.
Bleed air from hoses and break the vacuum by supplying
liquid refrigerant (R407C) to the discharge port near
the compressor until the pressure is equalized. This
holding charge allows the low pressure switch to
“hold” enabling the compressor to operate throughout
the process of charging the system.
Once the initial charge is completed, additional refrigerant
will need to be added with the unit running.
CAUTION
An adequate heat load must be supplied to ensure
a proper charge.
2.
Disconnect the refrigerant cylinder from the discharge
side of the compressor and connect it to the suction side.
3.
Start the A/C system and use the system controller to
lower the room temperature set point 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 Section
2.8.8
for the operating temperatures and pressures for the
type of refrigerant used in your system.
2.8.7.1
0 ºF Fan Cycling and -20 ºF
Variable Speed Control
The following instructions are for charging systems with
condenser fan cycling or variable fan speed control using
R407C refrigerant.
1.
Block off the intake air to the condenser with cardboard
until a constant discharge pressure can be obtained.
This will lower the possibility of overcharging (for units
with fan cycling only).
a.
R407C Refrigerant- Allow the discharge pressure
to rise to 325-350 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.
CAUTION
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 tempera-
ture measuring device being well insulated. The ideal
superheat temperature is 12-15 °F. Maximum allowable
superheat temperature is 20 °F.
4.
While monitoring the pressure, take a sub-cooling tem-
perature reading on the output side of the condenser.
The sub-cooling temperature 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 by using the system controller to enable a
call for dehumidification (lower the humidity set point).
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.
CAUTION
Remove the blockage to the air intake of the
condenser.
7.
Fill out the applicable sections of Warranty Registration
and Start-Up Checklist.
2.8.7.2
-30 °F Flooded Head Pressure
Control NOTE
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.
NOTE
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 2.8.7.
2.
The head pressure control valve setting is printed on
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 or remove refrigerant to lower 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 con-
firmed by viewing the level of refrigerant in the receiver
while the unit is running at an elevated discharge pres-
sure.
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