hp oil cut out! need big help please

[klobber]

hi folks, in need of despearate help, working on carrier semi hermetic compressor, flooded evaporator, cutting out at hp on oil switch at 8 bar..... what is it?, there has been a power cut..... starts straight away from panel however cuts out staright away.......please help

[install monkey]

oil pressure switch has a heater to act as a timer to delay the cut out of low oil pressure,normally this is 90-120 seconds,oil pressure switches only cut out on low oil pressure,is there a loose connection on the motor master or oil pressure switch.so when the compressor jolts on start up it breaks a connection??

[klobber]

im not onboard the rig im actin on behalf of somebody, he says it runs for 1min, oil pressure rises then cuts out when oil rises to 8 bar....... there is no hp lp switches...... he starts it from panel then above happens.... it is needed as temp is very high

[chemi-cool]

Make sure no liquid is coming back to the sump, it can drive the oil presure contlol crazy.

[klobber]

how do you mean crazy, what would your guess be?? no hp or lp switch.... water supply was recently off then back on 3 x the ususal flow rate when they started it....... they said the oil went cream.... then its now less movment???? please help....

[install monkey]

need oil,is the oil warm? crankcase heaters on carrier 06e's are 120watt. the bulls eye on compressor should be 3/8 to 3/4 full,if its been off for a while and been reset with a high demand the tev could be causing liquid to wash the oil from the sump into the system,best way to get it going without damaging the comp is shut the suction valve so it pumps down to about 3psi,manually pump in more oil.open suction valve,run it and moniter the oil level for the next 12hrs or so because when the oil returns back to the comp it will need draining

[chillerman2006]

they said the oil went cream...

do you mean the oil went white and creamy or was it just cloudy

white & creamy = water in oil

just cloudy would probaly be liquid refrigerant in the oil

crankcase heaters working ?? was the oil heated sufficiently before start up ??

[cadwaladr]

is the oil pressure switch mounted near compressor it sounds like its operating like an lp switch,what is the suction pressure are liquid line valves open,it sounds like it going into vacuum and oil switch is tripping if the water was off heat exchanger prob frozen?

[klobber]

The oil switch is next to compressor, when it starts it runs for 40 seconds, the suction stabilises at 60 psi, discharge rises to 165(cuts out at this point) oil rises to 9 bar then drops to 8bar(cuts out at this point)..... it is not going into a vaccuum...it is not cutting out on low oil...the oil is trying to rise in pressure!....they say its drawing alot of amps, well over what it should run at....... when they checked it this morning whilst it was off all night it had half oil level in sight glass... ran it few times (for 40 seconds) now when its sitting stable it has no oil level in sightglass..... could it be when they started up after power cut (they say the water supply was flowing double the pressure it should be) it has over condensed and liquid has went to compressor and the compressor is now not able to compress the liquid? still dont know what is cutting it out???? please advise.....

[Grizzly]

There are at least 3 forum members that have mentioned liquid contamination of the oil and it's consequences.
please read their advice again it is sound.
Grizzly

[chemi-cool]

Another thing that worth checking is the time.
An oil presure control has a resistor that acts as a heater for 90 seconds and then if the HP is not high enough, a bi metal cuts the control circuit off.

Your time is 40 seconds. Looks too short to me and might indicates that the oil presure control is faulty.

What type And make is your oil presure control?

[Gary]

What refrigerant is in the system?

Is the oil pressure control manual reset?

[Gary]

I'm not familiar with any oil pressure switches that trip on high oil pressure. Is there such a thing? They generally trip on low oil pressure.

[Gary]

they say its drawing alot of amps, well over what it should run at.......

This raises another possibility: The compressor trips on internal overload, the oil pressure control continues to time out and then trips, the compressor overload resets but the oil pressure control does not. Everyone thinks it tripped on oil pressure, when in fact it tripped on compressor internal overload.

[Gary]

If this is a three phase compressor, it is possible that one of the legs is out. The other two will run the compressor single phase, drawing very high amps. Turn off the power. Disconnect the leads at the compressor. Turn the power back on. Check the voltage on all three leads. If the voltage is okay, connect back up and check the running voltage on all three leads. If one leg has low running voltage, there is resistance in that leg (burnt contacts, burnt wiring, loose connections, etc.). A voltage drop across a contact tells you it is burnt.

[Royal241]

Very good advice. I had same problem for a few weeks. Customer kept on pressing the oil reset button. I changed the oil, cleaned the screen, pressure increased and thought I got it right. Well, after a few hours it tripped again, after defrost. Had a bad breaker. 3 phase, with a bad leg.