Advanced Scroll Temperature Protection (Astp) - Lennox FCM 85 Installation, Operating And Maintenance

A S
DVANCED CROLL
O M E
PERATION ODE XPLANATION

Protection is activated when Scroll Discharge
Port. Reaches 150°C (+/- 17K)

Compressor is protected as « Unloaded » but
continues to run

Protection mode balances
discharge/suction pressure
-
-

Motor protector opens (Klyxon)

Compressor turns off, cools

Motor protector resets, compressor restarts

Bi-metal disk resets before motor
protection

Cycle will continue until cause of
overheat is fixed
180
150
120
ASTP
Klyxon
90
65
Compressor Runs
40
Balanced
Pressures
0 20
DISC OPENS,
SCROLLS UNLOAD
IOM – FLEXY II – 0308 – E
T P
EMPERATURE ROTECTION
Motor heat builds inside
compressor
No refrigerant flow to carry
motor heat away
Temperature Behavior with ASTP Protection
Discharge
Port
40 60
Time (Minutes)
MOTOR PROTECTOR
OPENS, PUMP TURNS
OFF
(ASTP)
S C
ERVICE A OMPRESSOR

What to do?


DO NOT ASSUME A COMPRESSOR RUNNING
UNLOADED (BALANCE PRESSURE) IS A
FAILURE

Likely situations where protection may activate :

Initial system charging (or recharging after
servicing)

Field servicing (system problem causes
overheating)
Compressor
off
80 100 120
If a protected compressor is identified
-
Stop the compressor
-
Allow to cool thoroughly
-
Restart pump & check for
normal operation
-
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
-
Technician will observe
« Balanced pressures »
-
Risk of misdiagnosis as failed
compressor
-
Must stop pump, cool
thoroughly, reset
140 160
PROTECTOR RESETS,
PUMP RESTARTS FULLY
LOADED
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