3–9
T-340
3.4 Safety and Protective Devices
Unit components are protected from damage by safety and protective devices listed in
. These devices moni
-
tor 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).
Humidity Sensor (HS)
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
Controller
Setpoint Range
-30 to +30°C (-22 to +86°F)
Table 3–1 Safety and Protective Devices
Unsafe Condition
Device
Device Setting
Excessive current draw
Circuit Breaker (CB-1, 25 amp) - 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 current draw by the
Emergency Bypass module
Fuse (FEB)
10 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 mo
-
tor(s) winding temperature
Internal Protector(s) (IP-EM) - Automatic Reset N/A
Abnormal pressures / tempera
-
tures in the high refrigerant side
Fusible Plug - For Receiver
Rupture Disc - For Water-Cooled Condenser
99°C = (210°F)
35 kg/cm
2
= (500 psig)
Abnormally high discharge
pressure
High Pressure Switch (HPS)
Opens at 25 kg/cm
2
(350 psig)
