Cascade System Querry

[D.D.KORANNE]

A cascade system with R-404A refrigerant on high side designed for -35 deg C evaporating and 45 deg C condensing temperature motor tripping on winding temperature thermistor. The suction gas temperature recorded at suction valve is (-18) deg C with the gage pressure of 0.8 bar ; a clear 18 deg C superheat. Could the high suction superheat contribute to tripping thermistor while the envelop is withi limit?
OR ELSE WHAT COULD CONTRIBUTE TO MOTOR TRIPPING ?
KORANNE

[US Iceman]

High return gas temperature can cause the motors to heat up. Loose motor connections can also cause a higher than normal amp draw. Or insufficient motor cooling, i.e., no air flow on motor.

[Andy]

A cascade system with R-404A refrigerant on high side designed for -35 deg C evaporating and 45 deg C condensing temperature motor tripping on winding temperature thermistor. The suction gas temperature recorded at suction valve is (-18) deg C with the gage pressure of 0.8 bar ; a clear 18 deg C superheat. Could the high suction superheat contribute to tripping thermistor while the envelop is withi limit?
OR ELSE WHAT COULD CONTRIBUTE TO MOTOR TRIPPING ?
KORANNE

Faulty motor, winding problem

Worn compressor (check discharge temperature)

Kind Regards Andy

[Peter_1]

We last had a Bitzer (2 years old) which tripped on the internal thermistor (Kriwan).
Measured the values at standstill and at room temperature and there was a largz deviation from normal.
So, one of the thermistors is giving a false reading.
But this can't be repaired, so it runs now only on the overload relay.