Question of the week

[Pegleg Smith]

One of the fast food chain stores I service underwent a remodel of their dining room and restrooms last month. This all was to bring the store into better ADA compliance. All work done by the Hack Masters construction company. The contractors haven't completed the punch list yet.
One day last week all the new flourescent lights that were installed (6) plus some of the existing lights went dim. Not completely out but looking as if one of the tubes had gone bad, just sort of glowing. The syrup pumps and the carbonator pumps started chattering when they tried to run. The trash compactor motor also chattered. The energy manament system burnt out the motherboard. All these system have run for years with no problems.
Hack Master sent their electrician out to find the problem. He replaced the tubes in the lights and all the lights came back on. He said since he hadn't touched the circuits to the pumps and such that it wasn't his problem.
Yesterday the exact same thing happened. The EMS motherboard was replaced in the morning ( it cost $500.00 ) and by 3PM the lights and pumps were doing the same thing and the board burnt out again and more of the new lights were dimming. Even the incandescent bulbs were rapidly shutting off then on again.
The store owner is really pissed and he calls his own electrical contractor. This guy is worse than Hack Masters, in my opinion. He goes to the same panel that the other electrician went to, says he found some loose connections and everything is fine again. I do not beleive him. He reminds me of those gas and go A/C guys.
My question is Do you think Something is wired wrong and a circuit is backfeeding causing these problems? And if that might be the case how would I go about looking for the source of the problem? The store owner wants me to intercede on his behalf.

[Breeze]

Well since I did a gas and go a few times this week and last week I can't help you on this matter.

My guess would be bad ground somewhere, oh but wait i am not an electrician, oops. Maybe wolfy will have some ideas.

[JohnnyB]

I can't believe that the system could be wired to cause that intermittently. I had a building loose a leg of power that burnt out compressors and melted contactors but lights were either on or off. It seemed as though only 240v stuff tried to run on 120v and the current draw melted the contactors or the compressors just burnt out. One time I accidentally popped a breaker in a panel that had a "high leg" and it killed all the exits and EMs and the fire panel CB. Funny too, I went back the next day and the guy was putting in a new CB and I tripped the breaker back and then I realized what I was doing, then I heard the guy freaking out with his boss,.."I don't know it just fried out again" OOOPPPsss.
I just kind of snuck out real quiet like.

[Breeze]

I agree, you have to have a major wire loose somewhere. An IR tmom works great to find things like that with out touching them.
LAst breaker I had that would trip when it wanted to measured 150 something deg. I was the 3rd tech out there.

[workinlate]

Sounds like you have a weak leg pegleg...But you knew this....Doh!!!

[JohnnyB]

lights dimming makes me think of neutrals,.loose or maybe when they re-did the place they kept wireing things to the neutral bundles in the boxes without running back to panel and now the neutral that runs to the panel is over loaded. Maybe it only does something when some big load kicks on or off, thats why its intermittent. Each circuit should have a neutral thats big enough to carry the current back to the panel,right.

[Pegleg Smith]

I agree with most of the replies. I am under the opinion that the original electrician didn't wire in new breakers or pull new nuetrals, he just jumped power out of one of the junction boxes in the attic.
Doesn't code state that only 6 devices can be installed on any circuit? If that is the case then he has way too many lights on any given circuit. Then there is a requirement that receptacles needed to be installed along the ceiling perimeter. They put in 8 receptacles. Nothing is using the power at this time and I really can't see a need for these receptacles. The builder said it was code and had to be done.
If one of the high voltage wires from a ballast grounds against the light, would this backfeed voltage to ground and maybe cause this condition?

[JohnnyB]

Well, if anything shorted to the fixture chassis it should trip the breaker or buzz inside the fixture and in any case the light or lights wouldn’t work at that time. I know that when old HID and florescent light near the end of life they will draw more power, but I would think it would take quite a lot of bad bulbs to make a difference like what you’re describing. I did a bunch of High bay fixtures in a warehouse where half of the lights went out and they were blowing breaker. I went through 14 light fixchrs on a genie lift and found a short in a box that I think pulled short circuit current through a couple of ballasts and smoked them too. I ended up re-ballasting and lamping all the lights and when I did that I threw in an in-line fuse in each light.

[JohnnyB]

have you tried here yet...?

http://electrical-contractor.net/ubb/Forum1/HTML/003388.html

I get help from these guys too....I want to post the question as to why electricians dont like HVAC guys.

[jmac00]

called the power company, maybe the x-former outside is starting to go.

anyone put an ampmeter on the incomeing lines????

Johnny maybe correct: if they wired all the lights to one or two neutral lines, instead of running individual neutrals back to the box, your going to have problems.

the thing to do here (it will cost them) is to start turning things on one at a time, and watch an ampmeter,

intermitant problems are the absolute worse things to deal with,

heres a thought: take the lights out of the circuit and turn on all the other stuff with high amp draws, see what happens ???

[Breeze]

So why do electricians hate HVAC people? I didn't know that, it could explain a few things.

Maybe wolfdog knows why he hates us :)

[wolfdog]

It sounds like a loose neutral connection in a branch circuit feed.

There is no code requirement for the number of receptacles on commercial jobs. There is on residential.
On commercial jobs the code requires that receptacle load be calculated at 180 va per receptacle for general use receptacles. This applies to the load calculation.
I don't know about the 6 devices thing. Lights have to be figured at continuous duty which means 80% loading of the breaker.

[Pegleg Smith]

The electrician came in after the store closed Thursday night and worked on the panels. He said he found evidence of the neutral in one panel having burned insulation. He cut off the stripped end of three wires and there right at the end of the insulation you could see it looked melted. But the rest of the insulation looks OK. He also left what looks like a contact from a circuit breaker that was all pitted and burnt. The lights hadn't flashed all day so I hope that he corrected the problem.
If I had done the electrical in that store I would have 1 panel for the lighting, 1 for the receptacles, 1 for the 208v single phase loads, and 1 for the 3 phase loads. I had done this in a plastics plant I worked at once. It sure makes trouble shooting easier. All the panels would be from the same manufacturer, too. This store has , Allen Bradley main panel, ITT General sub-panels, Square D QO sub-panels, and a Siemens sub-panel. The various circuits go to whatever panel and you really have to search for the right breaker when you need to shut a circuit down. The breakers aren't marked properly either.

[jmac00]

when an electrician does not mark his circuits, thats just lazy and unsafe.when you have 80 circuits in a building you may need to get to a breaker real fast,searching for the one you need can be a real PITA

[diceman]

or neutral. I have seen that cause some crazy shit and it can be hard to find too. Not sure why the lights were ok when first replaced though, weird.