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#24599 - 04/16/03 02:06 PM Pulsing Lights
spyder Offline
Member

Registered: 10/14/02
Posts: 211
Loc: Massachusetts
Went on a service call for intermitent flickering lights today at a large residence. My first thought was loose neutral or connection. All connections checkout okay.

Of course the power quality showed not signs of trouble until I was ready to leave and the lights began to evenly pulse (not really what I would call flicker for about 30 seconds).

The house is feed underground from a pad mount vault type transfromer. This transformer feeds no other houses. My feeling is the problem lies with the transformer.

Has anyone ever encountered a similar problem or pulsing lights (not flickering or brown out)?

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#24600 - 04/16/03 04:03 PM Re: Pulsing Lights
Bjarney Offline
Moderator

Registered: 04/10/02
Posts: 2561
Loc: West-Southern Inner-Northeast ...
Many utilities have a loading gizmo that they can temporarily attach at a meter socket to flush out problems in their equipment and cables. It’s primary use is to show open neutrals, but it can also show other “hot-lead” problems.

On the customer’s side, sometimes rapping a rubber-handled screwdriver on electrical boxes containing splices or terminations may expose the problem. The trouble spot may show up as a noticeable temperature rise with a “back-of-the-knuckles test.”

Intermittent electrical problems can be hardest to locate. If you’ve spent a lot of time on one day snooping, tell the customer that you need to come back later when you’ve had a chance to thoroughly visualize, conceptually map and mentally explore all of the many components in their electrical system. ;-) Maybe the place was once a haunted disco, or needs some new Feng Shui.

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#24601 - 04/16/03 05:52 PM Re: Pulsing Lights
Electric Eagle Offline
Member

Registered: 04/20/02
Posts: 928
Loc: Alpharetta, GA
Was the house 15+ years old with an ITE/Gould panel? If so check the buss connection with the breaker and I'll bet some are burnt. It doesn't have to be ITE, but that's what I've seen most. I've also seen the same symptoms with a bad main breaker and a bad meter base.

Do you have an infrared thermometer? If so this can easily find loose connections because they will be much hotter than others.

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#24602 - 04/16/03 08:00 PM Re: Pulsing Lights
spyder Offline
Member

Registered: 10/14/02
Posts: 211
Loc: Massachusetts
New house, less than 5 years. All Squared D QO series. The distribuiton panel is Square D, NQOD. All connections/terminations seemed fine. Its a very large home with a 600 amp service, parrallel 350s, all copper, CT metering.

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#24603 - 04/16/03 09:23 PM Re: Pulsing Lights
Bjarney Offline
Moderator

Registered: 04/10/02
Posts: 2561
Loc: West-Southern Inner-Northeast ...
No dimmer in the circuit?

It possible, you may try temporarily putting much larger lamps in the fixtures to see if that affects the pulsing complaint. Clearly they could not be left in the fixture—only in your immediate presence during the test.

Sometimes the only solution is a methodical process of elimination.

{Is the 600A service single or three phase?}

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#24604 - 04/16/03 09:58 PM Re: Pulsing Lights
spyder Offline
Member

Registered: 10/14/02
Posts: 211
Loc: Massachusetts
Its a Single Phase Service. Yes, virtually all fixtures are on dimmers. The problem seemed to effect the whole house not just one circuit.

I just found out that they have been having trouble with a well pump. I wonder if when the well pump going bad kicks on that it effects the house voltage...I am going to check it out tommorow.

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#24605 - 04/17/03 10:03 AM Re: Pulsing Lights
Bjarney Offline
Moderator

Registered: 04/10/02
Posts: 2561
Loc: West-Southern Inner-Northeast ...
The dimmer question relates to the sensitivity of some lamp-dimmer combinations at a particular dimmer position...casuing more noticeable flicker.

Motor inrush is a likely cause of light flicker, but if it's the pump causing the problem--with respect to the "30 seconds", then it sounds like 'short-cycling' or some other starting-circuit problem.

Time for a clip-on ammeter and min/max voltmeter? Probably best if you can see the problem lights from the circuit-breaker panel. Watch starting current with lights on…maybe at night?

Be careful—it will soon be finger-pointing time.




[This message has been edited by Bjarney (edited 04-17-2003).]

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#24606 - 04/17/03 01:48 PM Re: Pulsing Lights
zapped208 Offline
Member

Registered: 02/18/03
Posts: 201
Loc: Somewhere in USA
spyder,- It could also be a short cycling compressor on a freezer or refrigerator.What is the time between pulses, any pattern?
_________________________
Shoot first, apologize later.....maybe

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#24607 - 04/17/03 02:10 PM Re: Pulsing Lights
spyder Offline
Member

Registered: 10/14/02
Posts: 211
Loc: Massachusetts
From what the owners say it happens at least once or twice a day. The pulsing I witnessed lasted about 20 to 30 seconds. Not super rapid, maybe two pulses per second at the most, but defintetly a very even pattern.

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#24608 - 04/17/03 02:25 PM Re: Pulsing Lights
Fred Offline
Member

Registered: 04/30/01
Posts: 461
Loc: Straughn, IN 47387
I had a similar situation a couple of years ago. It turned out that the well pressure tank was water-logged and the pump was kicking on/off several times in a row causing the lights to pulse. If they are having well problems, I'd look here first.

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