035-17311-000 REV A (1200))
Unitary Products Group
31
Should a low-pressure switch open three times within one
hour of operation, the UCB will lock-out the associated com-
pressor and flash a code (Table 33). If the other compressor
is inactive, the condenser fans will be de-energized.
FREEZESTAT
During cooling operation, if a freezestat opens, the UCB will
de-energize the associated compressor, initiate the ASCD,
and, if the other compressor is idle, stop the condenser fans.
If the call for cooling is still present at the conclusion of the
ASCD, the UCB will re-energize the halted compressor.
Should a freezestat open three times within two hours of
operation, the UCB will lock-out the associated compressor
and flash a code (Table 33). If the other compressor is inac-
tive, the condenser fans will be de-energized.
FLASH CODES
When the UCB has locked-out a compressor, the UCB will
initiate a flash code associated with the error. Also, if the
thermostat is so equipped, the UCB will energize the thermo-
stat trouble light.
RESET
Remove the call for cooling, by raising thermostat setting
higher than the space temperature. This resets any pressure
or freezestat flash codes.
LOW AMBIENT COOLING
To determine when to operate in low ambient mode, the UCB
has a pair of terminals connected to a temperature-activated
switch. When the low ambient switch is closed and the ther-
mostat is calling for cooling, the UCB will operate in the low
ambient mode.
Low ambient mode operates the compressors in this manner:
10 minutes on, 5 minutes off. The indoor blower is operated
throughout the cycle. The 5-minute off period is necessary to
defrost the indoor coil.
Low ambient mode always begins with compressor opera-
tion. Compressor minimum run time may extend the minutes
of compressor operation. The defrost cycle will begin immedi-
ately following the elapse of the minimum run time.
When operating in low ambient mode, the UCB will not lock-
out the compressors due to a freezestat trip. However, a
freezestat trip will de-energize the associated compressor. If
TABLE 30: 7.5 TON STANDARD EFFICIENCY SUPERHEAT CHARGING
Outdoor
Temp (°F)
Superheat at Compressor Suction (°F)
Airflow = 3000 CFM
Indoor WB Temp (°F)
55
57
59
61
63
65
67
69
71
73
75
65
10.6 13.5 16.3 19.1 22.0 24.8 27.7 29.1 30.5 32.0 33.4
70
8.4 11.1 13.8 16.5 19.3 22.0 24.7 26.5 28.4 30.2 32.0
75
6.1 8.7 11.3 13.9 16.6 19.2 21.8 24.0 26.2 28.4 30.6
80
-
6.4 8.9 11.4 13.9 16.3 18.8 21.4 24.0 26.6 29.2
85
-
-
6.4 8.8 11.1 13.5 15.9 18.9 21.9 24.8 27.8
90
-
-
5.8 7.9 10.1 12.2 14.3 17.2 20.2 23.1 26.1
95
-
-
5.3 7.1 9.0 10.8 12.7 15.6 18.5 21.5 24.4
100
-
-
-
6.3 7.7 9.0 10.4 13.5 16.6 19.7 22.8
105 -
-
-
5.5
6.4
7.3
8.1
11.4
14.6
17.9
21.2
110
-
-
-
-
5.1
5.5
5.9
9.3
12.7
16.1
19.5
115
-
-
-
-
-
-
-
7.2
10.8
14.3
17.9
TABLE 31: 10 TON STANDARD EFFICIENCY SUPERHEAT CHARGING
Outdoor
Temp (°F)
Superheat at Compressor Suction (°F)
Airflow = 4000 CFM
Indoor WB Temp (°F)
55
57
59
61
63
65
67
69
71
73
75
65
19.6 20.8 22.0 23.2 24.4 25.6 26.9 28.4 29.9 31.4 32.9
70
14.4 16.0 17.5 19.0 20.5 22.0 23.5 25.4 27.3 29.2 31.0
