20
Chapter 3
A. Internal Thermal Protectors
Internal thermal protectors are completely internal
and tamper-proof. They cannot be by-passed.
Single Phase Motor Thermal Protectors
Internal thermal protectors detect excess heat and/or
current draw. They are located in the following sin-
gle phase motors: AB, AW, AH, AV, and AG.
3-Phase Motor Thermal Protectors
The 31HM and 32HM on-winding motor protec-
tors are 3-phase line break, automatic reset devices
wired in series with each phase at the neutral point
and mounted on the windings. They are used in AB,
AG, AV, and AN models.
Table 3-2: Facts About Thermal Protectors
External Line-Break Thermal
Protectors
•
Currently used on all AE, AK, AZ, RK, and AJ models
•
Sense motor current and housing temperature or combination
thereof
•
Break line current when tripped
•
Generally do not protect against loss of charge
•
When, by design, no air flow passes over housing, a special
“static” thermal protector must be used
•
Are designed for specific compressors and their intended
application. Make no substitutions
•
Will not protect motor if compressor is operated outside its
evaporator temperature range
Internal Line-Break Thermal
Protectors
•
Currently used on all AH, AB, AV, AG, AW, and most AN and SF
models
•
Sense motor current and motor winding temperature or
combination thereof
•
Break line current when tripped
•
Generally protect against loss of charge
•
Will not protect motor if compressor is operated outside its
evaporator temperature range
•
Not repairable or replaceable
Line Voltage-Electronic Protection
Module
(NOTE:
For more specific details
consult the authorized wholesaler.)
•
Currently used on some AN and SF models
•
Employs use of solid state temperature sensors in motor
windings and compressor discharge muffler
•
Sensor resistance values change with temperature variations
•
Module will interrupt power to the contactor coil when resistance
values of sensors exceed the specified range. This power
interruption thus stops the compressor motor
•
Module provides protection against:
•
Abnormal locked rotor conditions
•
Loss of refrigerant
•
High compressor discharge temperatures
•
Excessive current conditions
•
Time delays of 3 to 5 minutes occur on power interruption or
sensor trip