The compressor exploded today.Why?

[Dad]

Originally posted by danvashon
My opinion: You had air in the system. causing dead short that ignighted oil gas mixture and boom.

that is the second time that air in the system has come up. this is not a common event for me. is it for anyone? which field, commercial or residential?

[RoBoTeq]

The compressor is grounded which makes the refrigerant lines directly grounded.

[resolutetech]

More then likely the compressor went into a vacuum arching internally causing the oil to combust.

are you saying air was in system to combust with oil or oil got very hot with short to ground and pressure caused blow out

[Edited by lusker on 05-15-2005 at 09:46 AM]

[Dad]

That is what is sounds like could be the culprit. Really glad it is not common.

[tinknocker service tech]

chances are with the compressor that hot the windings were on the way out and the overload was the only reason they didnt go before you got there. sooner or later it would have failed and boom anyway. if people would just relize when the house starts to get hot and they make the call turn the unit off then. but they dont and just let it run hopeing it starts to work by some act of god. had one once the coust called at 10pm and his wife could not breath assma. he said he kept turning it down since noon time and it just wouldnt get cold. the compressor was hot as ever when i got there and on over load. hosed it down till it was cool. found run cap was bad exploded. replaced cap checked the windings fired it up. was checking the unit over and the terminals let loose. what a fire works show it was. it would seem to me only that the matereil used to hold the terminals get to hot and break down to a point it can no longer hold up to the presure and let go. have seen a lot of blown terminals but that was the only time i was there when it happened. hope never to see it again iether

[Milk man]

External overload, was this an old unit?

I think the compressor was DOA when you got there. You just confirmed it. .

Could the discharge line been energized? Was the hot actualy being zapped?

My guess was grounded windings.

I've only seen ice machines with blow terminals. When the managers stand on the breakers because the snap in their fingers.

[RoBoTeq]

The way it has been explained to me by a Copeland engineer is that the unit either loses charge or due to a restriction the compressor goes into a vacuum. This causes high internal temperatures and electrical arching that happen faster then the safety shutoffs can react.

Air can either enter the system due to a leak in the low side of the system or directly after a compressor terminal has burned through. Either way it is correct that oxygen must be present before an explosion can take place.

I have most likely seen this more often then others due to my position of having to investigate this sort of failure. The company I repped for allowed me to take affirmative actions to get a new system installed as fast as possible with no cost to the consumer and as little cost to the contractor as possible no matter what the circumstances were that could have caused the problem. When this occurs, it is always a mess. If a homeowner was present when it occured, there is a need to make that homeowner feel comfortable with a replacement unit.

[Dad]

Thanks for the explanation Robo... I think that hits the spot.

[airamedic]

I finally understand why they call it a JUMPER wire!

You were the unlucky one that day. Glad you arent hurt. I dont think many others would have handled it differently. Your experience helps others remember to be a little more careful in our work.

[tim fox]

As I read Robo's reply to this post, I was reminded of a repair I did last year on A Trane Intellipak. I pumped the charge into the condenser as I've done on other units many times. And to get as much refrigerant in to the high side as I could, I let the low side go into a slight vac. Two days later at a copeland seminar, I found out that your not suposed to do that with a scroll for the reason Robo stated about the arcing in a vac. I was lucky nothing happened.this site is a great source of info!I consider it continuing education. Thank You Robo and many others here for sharing.

[RoBoTeq]

I used to pump refrigerant into the can myself, till it cost me a compressor replacement. That was on a recip which isn't as quick to happen as on a scroll. Live and learn.

[mark beiser]

Originally posted by RoBoTeq
I guess how well those dust/moisture covers stay on depends more on the holding clip. I know there are a lot of things we are supposed to do for safety, but how many of them do we really do? I can't ever remember seeing any tech put that cover back on until he was ready to button things up.

When I was in school, we got shown a safety film about the importance of never powering up a compressor without the terminal cover in place. The film was kinda gruesome and over the top, but I took it seriously.

My very first summer doing service work I had a service call on an old Lennox HS9 condensor that "keeps tripping breaker".
I didn't find any shorts to ground and the winding to winding resistances looked ok, but the compressor kept making a wierd sound for a few seconds before tripping the breaker.
Having seen a bad potential relay cause problems that seemed similar, I removed the wiring to it and tried starting the compressor again.

The compressor made a "chuchunk" noise and then the terminal block blew out. I was about 18" from it with it pointing directly at me. I was holding my Amprobe ACD-10 that was clamped around the start leed about 2 inches below the terminals.
I didn't suffer any injury because I put the plastic terminal cover back on after ohming the compressor out and it stayed in place and directed everythng out the bottom of the cover. It did blow one of the jaws off my meter though.

Actually, I did suffer some injury. I probably broke the world record for the backwards broad jump, and bruised my arse on a rock when I landed.

Never power up a compressor with the terminal cover off, especially if you are diagnosing a suspected electrical problem with the compressor.



[Edited by mark beiser on 05-16-2005 at 11:13 AM]

[RoBoTeq]

I hear ya Mark, and you are right. Don't mean I'll do it though

I just learned what to keep out of the way of when working.

[MikeJ]

Originally posted by mark beiser

[BNever power up a compressor without the terminal cover off, especially if you are diagnosing a suspected electrical problem with the compressor.

[Edited by mark beiser on 05-16-2005 at 02:15 AM] [/B]

Drop the out. For safety

[RoBoTeq]

Good catch Mike...we all knew what he meant but no one caught the typo.

[Shophound]

Originally posted by RoBoTeq
Good catch Mike...we all knew what he meant but no one caught the typo.

I did...but I'm just now reading this.

[mark beiser]

Woah, thanks for catching my typo, fixed it.
I'm real bad about typos because I'm usually thinking way ahead of what I'm typing and sometimes don't reread things.

[Edited by mark beiser on 05-16-2005 at 11:16 AM]

[RoBoTeq]

Well, ya know Mark, you are the only one on this forum that makes typo mistakes

[HVAC Pro]

Okay, something that has puzzled me a little. I have heard about the arcing of a scroll in a vacuum. But how do so many of them survive with a system restriction that has the scroll operating in a vacuum for days or weeks before someone gets there to check it? This one has always perplexed me. Seems like this condition would mimic a pumpdown.

[Milk man]

So the terminals won't blow out without oxygen? If you try to arc two wires together in a vacuum will it spark?

I've seen terminal blow out while someone holds the breaker. I doubt there was any air in the system.