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Lennox Fhm 170

Lennox Fhm 170
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ADVANCED SCROLL TEMPERATURE PROTECTION (ASTP)
FLEXYII_WSHP-IOM-1307-E - 56 -
OPERATION MODE EXPLANATION
v Protection is activated when Scroll Discharge Port.
Reaches 150°C (+/- 17K)
v Compressor is protected as « Unloaded » but
continues to run
Protection mode balances discharge/suction
pressure
- Motor heat builds inside compressor
- No refrigerant flow to carry motor heat away
v Motor protector opens (Klyxon)
Compressor turns off, cools
v Motor protector resets, compressor restarts
Bi-metal disk resets before motor protection
Cycle will continue until cause of overheat is fixed
SERVICE A COMPRESSOR
v What to do?
If a protected compressor is identified
- Stop the compressor
- Allow to cool thoroughly
- Restart pump & check for normal operation
v DO NOT ASSUME A COMPRESSOR RUNNING
UNLOADED (BALANCE PRESSURE) IS A FAILURE
v Likely situations where protection may activate :
Initial system charging (or recharging after servicing)
- Compressor is run with too little system charge
§ Very common on split system
§ Will result in very low suction pressures (<1.7
Bars)
§ Do not disable low pressure cutouts while
charging
§ Charge high-side with liquid first
Field servicing (system problem causes overheating)
- Technician will observe « Balanced pressures »
- Risk of misdiagnosis as failed compressor
- Must stop pump, cool thoroughly, reset
Temperature Behavior with ASTP Protection
40
65
90
120
150
180
0
20
40
60
80
100
120
140
160
Time (Minutes)
Temperature (°C)
DISC OPENS,
SCROLLS UNLOAD
Compressor Runs
Balanced
Pressures
PROTECTOR RESETS,
PUMP RESTARTS FULLY
LOADED
MOTOR PROTECTOR
OPENS, PUMP TURNS
OFF
Discharge
Port
Klyxon
ASTP
Compressor
off

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