Frequent compressor burn outs

[askannan]

Dear guys,
Best Wishes for all of you.
For the past 5 years i am facing the frequent compressor failures kindly suggest me to over come this failures.

[nike123]

What are the conditions with power supply. Burn out are in lot of cases connected with bad power supply.

[askannan]

The power supply is stable. ie 400V (+/- 5 v of variation) and the power failures is twice a week only.

[powell]

and the power failures is twice a week only.

Twice a week is a lot! Do these compressors have any sort of phase line monitors or surge protection devices installed?

[Pooh]

Are you cleaning the system after the burn out, have you checked for acid in the system?
If not there is your problem.

Ian

[nike123]

The power supply is stable. ie 400V (+/- 5 v of variation) and the power failures is twice a week only.

Twice a week! You certainly need good under voltage and phase loss/rotation protection.
Also, after change of compressor, did you fitted acid filters and controlled oil acidity, and change them in to normal filter after you assured that there is no acid in oil any more?
Did you checked and changed contactor when you changed compressor?

[Brian_UK]

Word .doc from Askanan

One of my customer having 300TR x 6nos of Screw chiller. The chiller package consists of 2 Nos vertical hermetic screw compressor. It has to maintain the chilled water temperature of 44 deg. F at ambient temperature of 105deg.F (max). One chiller package having two independent refrigerant circuit (case cade system). This is a flooded type chiller with air-cooled condenser (with fan staging control).

I am maintaining the discharge super heat below 50deg.F by using the liquid injection. The compressor dose not reach it’s RLA at any circumstances even though these compressors are failing frequently.

If any one came across this kind of problem kindly tell me what could be the problem. Kindly suggest me what kind of precaution to be taken to avoid this kind of problems.

[US Iceman]

Repeated burnouts on the same system is either due to one or two things.

Either system is not being cleaned out good or the electrical power is terrible. This sounds like a Dunham-Bush screw chiller and it should have phase loss/reversal protection already.

As nike123 pointed out you should also check the contactor. I have seen some where the power supply was OK on the line side of the contactor, but when energized the load side voltage variation was not good (contacts were burnt from arcing).

The power supply is stable. ie 400V (+/- 5 v of variation) and the power failures is twice a week only.

Is this the total variation or only between two phases?

[askannan]

Twice a week is a lot! Do these compressors have any sort of phase line monitors or surge protection devices installed?

There is Power Control Relay in the circuit which is taking care of phase reversal/ unbalance, phase failures and over /under voltage. Ther is no surge protection device in the system.

[askannan]

Twice a week is a lot! Do these compressors have any sort of phase line monitors or surge protection devices installed?

There is Power Control Relay in the circuit which is taking care of phase reversal/ unbalance, phase failures and over /under voltage.

[askannan]

Repeated burnouts on the same system is either due to one or two things.

Either system is not being cleaned out good or the electrical power is terrible. This sounds like a Dunham-Bush screw chiller and it should have phase loss/reversal protection already.

As nike123 pointed out you should also check the contactor. I have seen some where the power supply was OK on the line side of the contactor, but when energized the load side voltage variation was not good (contacts were burnt from arcing).



Is this the total variation or only between two phases?

It is the total variation

[askannan]

Twice a week! You certainly need good under voltage and phase loss/rotation protection.
Also, after change of compressor, did you fitted acid filters and controlled oil acidity, and change them in to normal filter after you assured that there is no acid in oil any more?
Did you checked and changed contactor when you changed compressor?

Before fix the new compressor into the burnout system we do throuh clean of the system by usig Trichloro ethylene. after that flush out the system with dry nitrogen. De-hydrate the system during vaccumizing by using strip heaters on the condenser coils. We replace the catch all drier in the oil return line with high acid / burnout core. After re commissioning the compressor we run the compressore for 12 hours and we do replace the compressor oil and catch all drier core. we use fresh refrigerant for this system

[nike123]

Did you checked first oil for acidity after replacing it with new one.
Did you checked new oil after some time for acidity?
Did you changed/checked contactor?

[nike123]

There is Power Control Relay in the circuit which is taking care of phase reversal/ unbalance, phase failures and over /under voltage.

What make and model is that power control relay?

[cmorris69]

Don't rule out intermittant flood-back with resulting spikes in amp draw. Those packages had literally no provisions for suction superheat and it was VERY common to experience slugging. Hard to beliveve, but early versions (without automated liquid metering valving) were critically charged and if you over-charged them just a bit, slug they would.

[kbrohit]

I have gone thru your problem statement.
In the same you have mentioned that you are maintaining superheat less than 50 Deg F which is quite higher.
Standard superheat setting will be from 15 to 20 Deg F.
For getting 44degF water temp what is your evap temp or suction pressure? And your discharge pressure?.
Have you checked the location and operation of TXV bulb for proper superheat?

Just let me know what are the operating parameters?

[750 Valve]

In the same you have mentioned that you are maintaining superheat less than 50 Deg F which is quite higher.
Standard superheat setting will be from 15 to 20 Deg F.

He means 50k DISCHARGE superheat - that is the discharge temps are maximum 50K above the saturated condensing temp and he is controlling them with liquid injection.

Like previously mentioned - have you changed the contactors on any of the comp changes?

[WINJA]

Are you sure you are putting compressors for the correct voltage rating back in , or are they wired for the correct voltage , some are star for high voltage and delta for low voltage , I worked on a york chiller a few years ago with dual voltage compressors it had 9 terminals on the compressor and some one got it very wrong .
also if its part winding start are you getting the sequence right and are both contactors staying in and drawing even amps?