Emerson PFH020A-L, User Manual

Page: 112 / 117

4.4 Field Charge Verification
An integral sight glass is provided with the receiver to assist in field charge verification. During charge
verification set the control temperature down to keep the system running. If the system is equipped with
hot gas bypass, de-energize it by removing power from the hot gas solenoid valve coil. To remove power,
disconnect the solenoid leads from the unit contactor in the electric box (refer to the specific unit
schematic;
Single-phase, 1-3 ton model schematic, typical on page 12 through Three-phase, 3-5 ton model
schematic, typical on page 13). When charge verification has been completed, replace and secure all wire
connections and covers.
During operation at design ambients (95 or 105°F; 35 or 41°C) the charge level will be above the sight glass
in the receiver. If levels are below the sight glass an undercharge condition is likely. If levels are above the
sight glass and higher discharge pressures than normal are observed an overcharge condition may be
likely. However, verify that other high discharge pressure causes such as dirty coil and restricted airflow
are not responsible before removing charge.
At temperatures below design ambient, refrigerant backs into the condenser coil and the level in the
receiver will drop below the sightglass. If you are trying to verify charge level at lower ambients, block the
condenser coil to maintain 230psig (1585kPa) discharge pressure to ensure the head pressure control
valve is closed. At these conditions the charge level should be above the sight glass in the receiver.
NOTE: The 5-ton high ambient, 5-ton Quiet-Line and 8-ton models consist of two condenser coils and
two receivers. When restricting airflow on these units, the coils should be blocked off proportionally. If
one coil is restricted significantly more than the other, liquid can remain in the restricted coil causing
lower levels in the receivers. The receiver liquid level should be above the sight glasses in both
receivers. There may be some variation in charge level between the two receiver sight glasses due to
piping and assembly variations. When adding charge, determine which receiver level is lower and use
that sight glass to gauge charge level.
NOTE: If no level is visible in the sight glass, add charge until the level is in the middle of the sight glass.
Check the discharge pressure during this procedure and adjust coil restrictions to maintain 230 psig
(1585 kPa). Once the charge is in the middle of the sight glass, add additional system charge per the
following table. After charging, unblock the coil and allow the unit to operate normally. After conditions
have stabilized, restrict the coil if required to maintain 230psig (1585kPa) discharge pressure and verify
that the charge level is above the sight glass.
Vertiv | Liebert PFH Installer/User Guide | 35