Holy Ghost in the machine!

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WesWalker

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We have been providing service to a church that was built seven years ago. Every motor on every piece of equipment has been replaced at least twice. Now I have two Sq D LXG lighting contactors - one for parking lot lights and one for building exterior lighting - that have stopped functioning (in the closed position) at the same time. The lights can be turned on/off with the CBs at the panel.

POCO has been out and hung a meter on the XFMR for a few days on two seperate occassions. They say there are no PQ issues on their side of the meter.

I have checked every terminal lug, verified all of the wire sizes that I could eyeball, verified all load calcs, voltage drop, etc. and everything in the system seems to be correctly designed and installed.

Any SWAGs or suggestions?:-?
 
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petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
EVERY motor? Single phase or three phase?

I have heard of bad batches of lighting contactors, where the latching mechanism fails, usually in the on position. Maybe check the Sq D website and see if there is a recall on these units.
 
beanland

beanland

Senior Member
Location
Vancouver, WA
Neutral Problems

Neutral Problems

I would look for bad neutral connections someplace. Have you checked voltage at devices & receptacles? Overvoltage will kill motors.

Did the welded contactors feed any failed ballasts? Did the OCPD operate?

Undervoltage also will kill motors from heat. Same thought. Check voltage at motor terminals operating and not.

Unbalance, if 3-phase could also occur. Do you have a few 3-phase motors and the rest single-phase lighting? Is the load balanced? Maybe the voltage unbalance is so bad that it is causing the 3-phase motors to overheat and fail.

Grab a good meter and go to work. No miracles today!
 
mdshunk

mdshunk

Senior Member
Location
Right here.
WesWalker said:
We have been providing service to a church that was built seven years ago. Every motor on every piece of equipment has been replaced at least twice.
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That makes no sense to me. When things don't make sense to me, that means the information provided is bad or there's missing information.

If I was on this job, my first order of business would be to install a recording power quality analyzer (volts, amps, disturbances, etc) on the main lugs of the MDP for a month or so, and go from there. The description of the problem is super crazy, in my experience.
 
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