T-359 3–8
3.4 SAFETY AND PROTECTIVE DEVICES
Unit components are protected from damage by safety and protective devices listed in Table 3–1. These de vices
monitor the unit operating conditions and open a set of electrical contacts when an unsafe condition occurs.
Open safety switch contacts on either or both of devices IP-CP or HPS will shut down the compressor.
Open safety switch contacts on device IP-CM will shut down the condenser fan motor.
The entire refrigeration unit will shut down if one of the following safety devices open: (a) circuit breaker(s); (b) fuse
(F3A/F3B, 7.5A); or (c) evaporator fan motor internal protector(s) - (IP).
m. Humidity Sensor Orange wire Power
Red wire Output
Brown wire Ground
Input voltage 5 VDC
Output voltage 0 to 3.3 VDC
Output voltage readings verses relative humidity (RH) percentage:
30% 0.99 V
50% 1.65 V
70% 2.31 V
90% 2.97 V
Table 3–1 Safety and Protective Devices
UNSAFE CONDITION DEVICE DEVICE SETTING
Excessive current draw
Circuit Breaker (CB-1) - Manual Reset Trips at 29 amps (460 VAC)
Circuit Breaker (CB-2, 50 amp) - Manual Reset Trips at 62.5 amps (230 VAC)
Circuit Breaker (CB-2, 70 amp) - Manual Reset Trips at 87.5 amps (230 VAC)
Excessive current draw
in the control circuit
Fuse (F3A & F3B) 7.5 amp rating
Excessive current draw
by the controller
Fuse (F1 & F2) 5 amp rating
Excessive condenser fan
motor winding temperature
Internal Protector (IP-CM) - Automatic Reset N/A
Excessive compressor
motor winding temperature
Internal Protector (IP-CP) - Automatic Reset N/A
Excessive evaporator fan
motor(s) winding temperature
Internal Protector(s) (IP-EM) - Automatic Reset N/A
Abnormal pressures/tempera-
tures in the high refrigerant side
Fusible Plug - Used on the Receiver 99C = (210F)
Abnormally high
discharge pressure
High Pressure Switch (HPS)
Opens at 25 kg/cm
2
(350 psig)
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