Carrier 38APS025 - A140 - Reverse Rotation Detected; Maximum Saturated Condensing Temperature

171
A140 — Reverse Rotation Detected
Criteria for Trip: The alarm criterion is checked when the first
compressor in a circuit is started. The control writes the value
of the suction pressure 5 seconds before starting the first com-
pressor in the circuit. At the time the compressor is started,
another reading is obtained. A rate of change is calculated
based on the two values and extrapolated to the expected value
5 seconds later. The suction pressure is obtained 5 seconds
after the compressor has been started. If the suction pressure is
not at least 1.25 psig (8.62 kPa) lower than the expected value
or the upper limit for proof of proper rotation, a reverse rota-
tion alarm is declared.
The example below lists sample suction pressures of a starting
circuit. Figures 189 and 190 show reverse rotation detection
for this example.
a38-7400
Fig. 187 — Maximum Saturated Condensing Temperature ( °F)
a38-7401
Fig. 188 — Maximum Saturated Condensing Temperature ( °C)
TIME
SUCTION
PRESSURE
psig (kPa)
SATURATED
SUCTION
TEMPERATURE
°F (°C)
t=–5 (5 seconds before
compressor start)
200.4 (1382) 70 (21.1)
t=0 (compressor start) 197.1 (1359) 69 (20.6)
t=5 (5 seconds after
compressosr start)
169.6 (1169) 60 (15.6)