# Bad Phase?



## Greg (Aug 1, 2007)

Did you check for a loose or arcing neutral? That sure looks like a symptom.


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## McClary’s Electrical (Feb 21, 2009)

sparky25 said:


> Has anyone seen or have insight into this issue:
> 
> Our building is fed by a 3-phase wye shared neutral and sent to individual units as 120/208. On one of the phases the voltage will, about once a month, show individual issues such as:
> 
> ...


 


I've seen a 750 padmount xfmr with a loose connection on the fuseholder for "c" phase. It caused the exact symptom you're describing, It took a long time to find, as you're seeing now. People point fingers back and forth and it really didn't get fixed until it started blowing the c phase fuse once a month and they eventually changed the xfmr


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## 220/221 (Sep 25, 2007)

> The other 3 phases in the building do not reflect this


The other *2 *phases or the other 3 phase panels in th ebuilding?

You need to move your test equipment up the line and see where it stops, if it does.


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## RIVETER (Sep 26, 2009)

I have no reason why the once a month scenario but I have had a loose utility splice at the transformer pole and when the wind would blow it would do as you described.


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## sparky25 (Sep 28, 2009)

*tried it all*

An electrical engineering company went through the building and checked all the main lugs, transformers, etc. to make sure nothing was out of the ordinary physically. They issues a report stating is was most likely the power utility.

That got us no where quick.


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## varmit (Apr 19, 2009)

Possibilities:
Faulty breaker somewhere in system. Try infrared scan.

Panel bussbar connection loose.

Is service wire aluminum? Possible bad connection could heat up under load.

Loose fuse holder anywhere - POCO high voltage line, service, or local panel.

Loose or corroded terminations.

Transformer winding bad.

Is service underground? A conductor could be damaged and either be partially burnt in two, or causing a high resistance fault that does not trip a breaker. ( The UG conduit will be full of water.)

Just some ideas. Good luck.


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## Electric_Light (Apr 6, 2010)

Does it have an elevator? If one of the lines was dropping, the elevator would single phase and it would certainly get pissed since a three phase motor can not start on single phase. If the elevator doesn't act up, then I would think its neutral related or something downstream of service entry.


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