Compressor rotation reversed, damages??
Was on vacation last week and got a panic call from work yesterday that the entire building had no A/C. The electrical contractor that was suposed to swap in the new service on Monday (when I would be there) did it on friday because thats when the utility co. was avaiable.
I had 1 of the maintenance guys check all the units for air flow by feeling the registers, he reported no or very little air flow. I told him to shut then all down as the it looks like the phase rotation to the entire building has been reversed.
The units are as follows
2 5 ton York packaged units (recip compressor)
1 8 ton York packaged unit (recip compressor)
1 Trane 14 ton packaged unit (with replacment copeland scroll compressors)
1 3 ton split (recip compressor)
1 1/2 horse copeland refrigeration split (recip compressor)
These units had run about 5 hours with reverse rotation. I had him swap 2 leads on the disconnect on the Trane and start it back up so the main area would have cooling, he said it's worling fine. Guess the scrolls lived.
Now the question that I am going to answer at a meeting on Tuesday, has anything been damaged. I say this will have shortened the life of the compressors for the followng reasons.
1 the Yorks and the 3 ton split are 8 years old and the crank bearings have a wear patern in 1 direction. They now have 5 hours of run time in reverse, most likely sluging liquid the entire time because the evap air flow was non existant as the 3 phase fans where runing backwards. The condensor fans are single phase so they ran in the proper direction
2 the Tranes with the 6 month old Copeland scrolls do not pump while runing in reverse so they must have been cycling on internal overload due to over temprature of the motor. The 3 phase evap fan was runing backwards but since scrolls do not pump runing backwards no slugging
3 the copeland refrigeration (semi herm) is a 4 month old replacment compressor so I do not feel there is to much of a bearing wear patern there and it had normal air flow as the evap fan is single phase. I am not woried about this one
I also need to contact the Elevator company to ask if the hydralic pump can be damaged by reversing rotation, anyone know the answer to this one.
Opinions and addtions to my list please, I want to have all bases covered.
Your right about bearing wear being highly directional on journals, and liquid slugging so look for at least weakened capacity results. On the elevator pump if it is the old style impeller type I would say look for same bearing direction wear problem to be an issue maybe. 5 hrs on elevator pump not likely except for the high heat gain at the bell housing is not good.
you know with future damage possible/probable, you may not be able to place blame,
but its a good idea to get the owners of the equipment ready for damages to occur!
this kind of thing would make me real upset if it was one of my jobs
but the damage has been done, look at the bright side (job security)
Why did Mr. Sparky change phases...??Mark em and wire back the same....
I would blame him.....Not that that helps now...
I don't know the whole story either...
Life goes on long after the thrill of living is gone.
The plot unfolds, Mr. Sparky arrived on the job without a phase rotation tester. He was loaned 1 by our mantenance staff and used it to check that the utility co. connected the new service with the same rotation as the old service. He then returned the tester.
He then went on to extending and moving all the building feeders from the old service to the new one that had been built 20 feet away from the old one. This service replacment also included a new 400 amp transfer switch and 125kw generator, guess what. We found out that the phasing between the utility and generator is also reversed. Sure glad the transfer switch is smart and reported a "Phase mismatch" when put into test mode. Would have hated to see what could have happened if this thing had transfered with reversed phase rotation.
These are all small units and did not have Phase Rotation Monitors, I have been told that the Elevator does have one so hopefully no damage was done there. Will confrm that with the elevator service co. on Monday.
So much for a stressless return from vacation, on Monday I get to go thru all the 3 phase loads (A/C, fans, Pumps, Commercial Dishwasher, air compressor and even the siren on top of the firehouse) and check rotations and damages. Then I get to write a report listing possiable damages.
My boss was asked by the sparky's boss on friday night while they where swaping rotation on the critical things (while I was on the phone telling them what to look for) "do you want me to send a guy on Monday". He was told that Kevin (me) works better alone. He's right I may just want to hurt this guy.
Hope you had a good vacation.....
Ya might need another one soon....
Life goes on long after the thrill of living is gone.
God Bless our Veterans
God Bless the USA
had a call where 2 new 3PH RTU's were installed on a roof that only had 1 RTU .. electrician had to run wires from panel for these ... these were installed in the winter ... electrician was there on next day & i get to go there for the first time in the spring .. found bad contactor, scroll shorted to ground .. pretty bad burnout as well .. i do not know how long in time span this thing was operating backwards but it couldnt have been too long as these people called right when they noticed there was no cooling
Your are absolutely right about concerning oil. That's the only thing to fear about, those compressors the reciprocants and scroll (basically the last one are equiped w/reverse rotation disconecting for a short period- the recip no problem).
I recomend you that take all the amps, check with the nameplate and if some bearing have problem will show, other wise be calm. Check the refrigerant pressure because if the pump to much oil, the valves are usually damages.
Got out there today and checked out all units, all the recips appear to be runing fine, the scroll must have run real hot as the copeland label (data plate) is all curled up and has shrunken about 1 1/2 inches. It is located at the bottom of the compressor shell mostly below the oil level, that oil must have gotten real hot.
I ran it for a while and gave it a quick sniff test, it does not smell burnt it is drawing normal amps and has normal pressures. Will do an acid test in the morning and a follow up in a month.
Also found several exaust fans, a commercial dishwasher and the firehouse siren running backwards. The only thing that was right was the Elevitor hydralic pump.
It apears that the utility feed was reversed when they made thier connection and the sparky never checked it as he did not have a rotation tester. He had borrowed ours early in the day but returned it and said he did not need it anymore. The bad thing is that the phase rotation between the utility and the emergency generator was also mismatched. The transfer switch electronic controls caught this and would not allow a live transfer. Good thing, I bet you could break some crankshafts that way.
Sparky will be put on notice that he owns the A/C compressors for the rest of the cooling season. I am more worried about the dammage to the recips from flood back than I am about bearing wear. The scroll, guess we will see how that plays out.
i have seen a scroll run backwords for almost two weeks. you can't kill a scroll there tough as hell. 5 hours would do very little damage if any at all.
that was 7 or 8 years ago
you can kill a scroll. trane scrolls are not very forgiving. copelands seem to not have any problem. i am not sure about other designs.
Originally Posted by desroches
i can not tell you the number of times that i have run into a COMMERCIAL/INDUSTRIAL eletrician, and he does not have a phase rotation meter. he might as well not have an electrical meter either, since it seems that they do not know much about electricity. i know that i am generalising...but how much hell would we get if we borrowed the only set of manifold guages that our shop owned...i am down off of my soap box now. thank you.
Someday, I hope to be just as brave as Harry Stamper.
This brings up a question I've had for a long time, that has never been satisfactorily answered by an electrician. A few years ago, I worked at a hotel that was in an area subject to a lot of electrical storms. Whenever the substation went down, they would swap legs before bringing it back online. I didn't have many three phase machines, but I did have a couple scrolls that would be extremely hot and making awful noises by time I got to work and heard about it. I would swap legs on the machines and they were still running last time I heard. I called the local electric utility and asked why they routinely swapped legs, and everyone I spoke to told me that that is just the way they do things. No other explaination. I've asked several master electricians why this is so, and they said the same thing. It seems to me that there has to be some reasoning behind this beyond "That's just the way it's done". Is there some logic to this that I'm missing?
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