Stulz CeilAir CW - ºF Fan Cycling and -20 ºF Variable Speed Control

53OCH0006F08/13/2024
CEILAIR
®
CW & DX IOM
2.8.7.3 0 ºF FAN CYCLING AND 20 ºF VARIABLE SPEED CONTROL
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. Refrigerant R407C operates at a
lower pressure than R410A. When fine tuning the charge, ensure the pressures are correct for the type of
refrigerant used. Refer to Table 12 and Table 13 in section 2.9 for the operating temperatures and pressures
for the type of refrigerant used in your system.
2.8.7.3 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 or R410A 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: Raise the discharge pressure to 260315 psig (1.792.17 MPa) and hold it constant.
b. R410A: Raise the discharge pressure to 445480 psig (3.073.31 MPa) 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 temperature measuring device being well insulated. The ideal amount of superheat is 12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
condenser. 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 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.
CAUTION
Remove the blockage to the air intake of the condenser.
7. Fill out the applicable sections of Warranty Registration and Start-Up Checklist.