internal thermo switch

[philjd26]

hi, i was wondering can someone explain why a compressors internal thermo strip may activate..even though.. the gas charge is ok.. compressor mechanical parts ok..all others like fans coils etc are ok..and installation in general seemed good..have come across this on some compresssors!

cheers

[chillin out]

It is probably going O/C because of high current.

Check the resistance of the windings according to the manufacturers specification.

Chillin

[philjd26]

It is probably going O/C because of high current.

Check the resistance of the windings according to the manufacturers specification.

Chillin

hi chill,ye have done that before all windings balanced,however a little leakage to earth,was wondering does current get drawn from the slight grounding in some way???

[US Iceman]

Those are heat sensitive, so look for things that might contribute to higher than normal heat.

High suction superheat
high discharge pressures
broken discharge valves will add a lot of heat
low voltage
loose connections on motor or starter

Those are some quick things I can think of.

[taz24]

hi, i was wondering can someone explain why a compressors internal thermo strip may activate..even though.. the gas charge is ok.. compressor mechanical parts ok..all others like fans coils etc are ok..and installation in general seemed good..have come across this on some compresssors!

cheers

Most compressor motors are wound with a thermal sensor in each phase, so a 3 pase comp has three in series wound deep into the windings.
If as you say everything is fine with the comp then I would check the thermistor modual itself.
They have an internal relay that can fail.
With normal running they can trip and then once the comp has been reset they run as if there was no problem.
If in doubt and if you have proved all is well with the comp then change the thermistor modual.

taz.

[Dr._Fleck]

Is it a Maneurop compressor?

They need some cool gas back to stop them overheating.

Earth leakage is unlikely, 1000v megga test it though.

[frank]

Is it a Maneurop compressor?

They need some cool gas back to stop them overheating.

All compressors need this

[chillin out]

I think he meant that maneurop rely on some liquid returning to the comp to keep it within working specs.

Chillin

[philjd26]

Thanks for the comments lads.but sorry forgot to mention that these compressor i come across are inverter driven, and has a thermo switch connections on the shell with phase connecrtings...compressor runs for a while however not 100%... could it be the high volts/frequencey when looking for more duty that makes thermo open....all conditions i said at the start still apply another words every thing seems to be good however slight grounding..

[taz24]

..

It's not a klixon is it?
Klixons will activate if the running amps go up not just temp.

taz.

[old gas bottle]

there fitted for two things,over current and overheat,or on three phase machines ,mainley over temp,unless its something like a star point protector[old stuff now] witch does both on most machines ,over about 1 horspower most have contactors and overload units for overcurrent protection/phase loss and if the compressor is stressed and getting hot the current should go up anyway and trip,no expert on inverter yet as not had many breakdown, there are inverter checkers available now but make sure the systems good first. could be a long thread this as theres to much to say in one go !

[monkey spanners]

It could be due to high discharge superheat if it is mounted on the compressor body. In many ac compressors the body is open to discharge pressure and temperature, this is why they often run very hot to the touch, this is done to use the compressor body as a discharge muffler to keep the noise down.
The manufacturer should be able to tell you what temperature it should switch at, you can then check this with an infra red thermometer. Maybe the thermal overload is faulty.

Cheers Jon

[philjd26]

thanks for the comments... was also wondering what is the name for the waxy stuff that motors are wound in,and any ideas what makes this stuff break down apart from moisture and heat,........

cheers