Repeated Compressor Terminal Blowout

[Husky250]

Hi All,

I have encountered multiple systems lately that have experienced very similar problems. I have found several compressor terminals blown right out of the rotary compressors. All refrigerant gone obviously from the compressor terminals blown out. Can you guys give me all the most probable causes of the compressor blowout? I have a couple in mind, but would like to hear all possiblities from you guys. Thank you in advance!

Husky

[Gary]

Single phase or three phase?

[brunstar]

my gosh, not good, are these systems on 410A refrigerant?
what make of unit?

What the cause is some of the time is compressor failure down to earth which allows the fault current to heat the pressed metal plate out that holds the terminals away from the steel compressor casing.
it is a combination of the fault current and high pressure within.
what brand of unit is it?

[Husky250]

Single phase....PSC compressor.....Sorry I should have listed that information

[brunstar]

if you test it you will probably find it will be down to earth.

[Husky250]

my gosh, not good, are these systems on 410A refrigerant?
what make of unit?

What the cause is some of the time is compressor failure down to earth which allows the fault current to heat the pressed metal plate out that holds the terminals away from the steel compressor casing.
it is a combination of the fault current and high pressure within.
what brand of unit is it?

The systems are 410A and the make of the unit is LG. The LG units I have checked have the dual compressors. Compressor A (the largest capacity) seems to be the most common one to blow the terminals.

I wanted to know all possible situations that could cause such an occurance.

Thank you!!!

[Husky250]

if you test it you will probably find it will be down to earth.

That was one possible situation I thought of as well. Are there any other possiblities?

Thank you

[brunstar]

bearings going in the compressor which could then short out the windings

[Gary]

Are these units at the same location?

[Husky250]

Are these units at the same location?

No...they are at different locations. The grand total of systems I have encountered was three all at different locations.

I bet you are thinking voltage drop...I too suspected that, but voltage was OK at the locations at the time of service.

[Gary]

Yes, I was thinking voltage drop.

It seems doubtful that all three would ground out, but that's not impossible.

All they seem to have in common is the brand name and rotary type compressors.

Are these systems self contained?

[Gary]

In the thread title you said "repeated". Did you mean repeated or multiple?

[Husky250]

Yes, I was thinking voltage drop.

It seems doubtful that all three would ground out, but that's not impossible.

All they seem to have in common is the brand name and rotary type compressors.

Are these systems self contained?

Yes...they are self contained.

[Husky250]

In the thread title you said "repeated". Did you mean repeated or multiple?

Sorry....The proper word should have been multiple.

Since compressor A is the first to start (so it seems) I wonder about liquid slugging. Could liquid slugging cause the compressor terminals blow out?

I dont think the rotary compressor contains a relief valve. The compressor terminals are on the top side of the compressor. I suspect the compressor terminals are on the high side of the system. I may be wrong, but I wonder if liquid is either on the top of the compressor or returning to the compressor, could it be possible to blow the compressor terminals to blow out?

Thank you,

[Husky250]

Yes...they are self contained.

I just read the original post more closely. The systems in questions are LG Mini Splits...Split systems and not package units.

[Gary]

Rotary compressors come with an accumulator on the side of the compressor... for a reason. The inlet gas goes straight to the pump section. The rest of the compressor is on the high side. (That's why the body of the compressor is hot)

If the systems are self-contained, then I would suspect they are factory charged and the accumulator is sized to handle a floodback. But if the charge was increased in the field, then all bets are off.

Yes, a liquid slug could overload the compressor and the heavy amp draw could blow the terminal.

[Gary]

I just read the original post more closely. The systems in questions are LG Mini Splits...Split systems and not package units.

If the evap(s) are higher than the condensing unit, then during the off cycle liquid can gather in the evaporator, drain into the suction line and accumulator... and then flood back into the compressor on startup, especially if the refrigerant charge exceeds the capacity of the accumulator.

[Magoo]

For crying out loud. The terminals are tracking with moisture. If terminals are blowing out, insulate them with non-corrosive silicon, the natural cure stuff, or at least that putty compound.
magoo

[Gary]

I'm not sure what crying out loud has to do with it, but moisture is another possibility.

[Yuri B.]

Blown terminals may be only a consequence of combination of high temp and high current which become critical at some point. The more so if the terminals are not screws but those blade snap-on connections. At first something is happening to the system and refrigerant charge. (Lack of maintenance - such as dirty condensers, their not very good disposition, too much load on evaps, etc)

[Yuri B.]

And dozens and dozens of other causes - you ref engineers know them better than me. I mean, you should not have accentuated on the blown out terminals at all (the first post).

Those snap-on connectors become very very loose indeed with time, due to thermal expansion.

[Yuri B.]

Guys, I did not understand what was meant by "compressor terminals blown out". Refrigerant left here "obviously," or there were actual holes near the teminals with some marks of oil beneath the compressors?
Husky, I would ask the clients about who and when installed the units, I surmise the units are of one and the same batch, "obviously", a defective one (probably it might be useful to look at the plates on the units). I heard LGs are not the best ACs on the planet.

[Husky250]

If the evap(s) are higher than the condensing unit, then during the off cycle liquid can gather in the evaporator, drain into the suction line and accumulator... and then flood back into the compressor on startup, especially if the refrigerant charge exceeds the capacity of the accumulator.

Gary,

I think your idea is probably what is going on. I was not involved in the installations. Judging from the looks of the installation I think a gross over charge is very possible. The accumulator looks small, so I guess factory data plate amount is about all the accumulator will hold. I will continue to investigate for any additional clues.

You have sparked my mind on rotary compressors. Do you know where I can obtain any breakdown documents or sequence of operation for the rotary compressors?

Thank you and all for the assistance!!!

[nike123]

You have sparked my mind on rotary compressors. Do you know where I can obtain any breakdown documents or sequence of operation for the rotary compressors?




http://www.lge.com/DownloadJsp.jsp?filePath=/download/product/component/&fileName=CompressorTechnicalGuide_eng.zip

[lowcool]

could be inferior metal or porosity in connector or terminals themselves creating hot spot etc.they should be able to withstand locked rotor amps no matter what ever else is going on in the system.castings have been known to go porous too.are they blowing inside of compressor? or external.whats the sealant around terminal legs,is it a fusite type,sounds like crap manufacturing to me

[gwynn jones]

SNIP..... Are there any other possiblities?
Thank you

I had this happen a few times on compressors in a supermarket - I believe it turned out to be overly high superheats

[Magoo]

Hi Gary, to explain the term "for crying out load "is a simple exclamation statement, OK localized.
But here with a/c and general refrig systems compressor sweating is a problem at certain times of the year.
magoo

[Gary]

Hi Gary, to explain the term "for crying out loud "is a simple exclamation statement, OK localized.


Hi Magoo

Yes, I'm familiar with the term. I was just joking with you about it having nothing to do with crying. Just a little play on words there.