Emerson Precision Cooling For Business-Critical Continuity Figure i - Manual (Page 34)

Maintenance
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4.4 Field Charge Verification
An integral sightglass 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
specific unit schematic; reference Figures 7 through 10). When charge verification has been com-
pleted, 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 sightglass an undercharge condition is likely. If levels are
above the sightglass and higher discharge pressures than normal are observed an overcharge condi-
tion 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 230 psig (1585 kPa) discharge pressure to ensure the head pressure con-
trol valve is closed. At these conditions the charge level should be above the sightglass 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 sightglasses in both receivers. There may be some variation in charge level between the two
receiver sightglasses due to piping and assembly variations. When adding charge, determine
which receiver level is lower and use that sightglass to gauge charge level.
NOTE
If no level is visible in the sightglass, add charge until the level is in the middle of the
sightglass. 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 sightglass, add
additional system charge per Table 22. After charging, unblock the coil and allow the unit to
operate normally. After conditions have stabilized, restrict the coil if required to maintain 230
psig (1585 kPa) discharge pressure and verify that the charge level is above the sightglass.
Table 22 Field verification charge
Model Numbers R-407C
60 Hz 50 Hz oz (kg)
PFH014A-_L PFH013A-_L
4 (0.11) PFH020A-_L PFH019A-_L
PFH027A-_L PFH026A-_L
PFH027A-_H PFH026A-_H
18 (0.51)
PFHZ27A-_L PFHZ26A-_L
PFH037A-_L PFH036A-_L
PFH042A-_L PFH041A-_L
PFH037A-_H PFH036A-_H
8 (0.23)
PFHZ37A-_L PFHZ36A-_L
PFH042A-_H PFH041A-_H
PFHZ42A-_L PFHZ41A-_L
PFH067A-_L PFH066A-_L 18 (0.51)
PFH067A-_H PFH066A-_H
50 (1.42)
PFHZ67A-_L PFHZ66A-_L
PFH096A-_L
3-ton circuit
5-ton circuit
PFH095A-_L
3-ton circuit
5-ton circuit
18 (0.51)
18 (0.51)