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What's the problem? #1795
05/31/01 10:39 PM
05/31/01 10:39 PM
B
bhester  Offline OP
Member
Joined: May 2001
Posts: 38
I had a guy ask me what would cause all of his lights to dim whenever a motor would kick on. The house is around 2200 sq ft it has gas heat,water heater, and cooktop.He claime the electrician has changed the service disconnect and still no fix ,the checked the panel for loose connections the only solution was either the wire from the transformer was to small or the service entrance cable could have a nail or something in it.He said whenever the refrigerator kicks on the lights dim as the washer, and the A C any solutions?

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Re: What's the problem? #1796
05/31/01 10:58 PM
05/31/01 10:58 PM
sparky66wv  Offline
Member
Joined: Nov 2000
Posts: 2,236
West Virginia
It's pretty common for the inrush current of motors to dim lights; most residential Xformers are about 25KVa (Good for about 104 Amps at 240V) and split between 2 to 4 200A services. It's easy to imagine that even under diversified loads, peak times could test the Xformer's ability to provide steady voltage.

If #14 was predominantly used and used in long homeruns, then voltage drop would be aggravating a poor situation.

I think Scott35 refers to this phenomenon as Flicker factor .


[This message has been edited by sparky66wv (edited 05-31-2001).]


-Virgil
Residential/Commercial Inspector
5 Star Inspections
Member IAEI
Re: What's the problem? #1797
06/01/01 10:19 AM
06/01/01 10:19 AM
R
Redsy  Offline
Member
Joined: Mar 2001
Posts: 2,056
Bucks County PA
The voltage drop on a system that is a result of motor starting currents is probably most noticeable on incandescent lighting. This is due to the fact that the relationship between applied voltage and light output is not linear. For example, a 15% reduction in voltage could translate into a 40% reduction in light output.

It might pay to invest in a few compact fluorescent bulbs for the most annoying locations to see if they ride through the motor starts with less noticeable dimming.

[This message has been edited by Redsy (edited 06-01-2001).]

Re: What's the problem? #1798
06/01/01 01:09 PM
06/01/01 01:09 PM
sparky66wv  Offline
Member
Joined: Nov 2000
Posts: 2,236
West Virginia
Good Point and very well explained...

Man I love this forum!

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-Virgil
Residential/Commercial Inspector
5 Star Inspections
Member IAEI
Re: What's the problem? #1799
06/01/01 06:51 PM
06/01/01 06:51 PM
Tom  Offline
Member
Joined: Jan 2001
Posts: 1,044
Shinnston, WV USA
I think Redsy is on the right track, there is almost a 3 to 1 reduction in light output versus voltage drop.

Take a look at the pole & see how many services are connected to the transformer. If more than 3 or 4, could be too much load.

Another thing that can be tried by a qualified person with extreme caution is to measure the voltage drop at the weatherhead. if the VD is high, pretty well narrows it down to a power co. problem.

Tom


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Re: What's the problem? #1800
06/02/01 12:39 AM
06/02/01 12:39 AM
B
bhester  Offline OP
Member
Joined: May 2001
Posts: 38
Thanks for all the info,I'm unsure of what wire size was used but I think they used #12 for homeruns and #14 to the lights. I was told there was a vacant lot next to the above ground Xformer.It wouldn't suprise me if they didn't load the circuits with 12-13 lights on a 15 amp circuit in my opinion might be some of the problem and I know the next time I see him I'll probably be going over to investigate myself (aaaaaagh) I hate troubleshooting others mistakes.

Re: What's the problem? #1801
06/02/01 09:10 AM
06/02/01 09:10 AM
S
sparky  Offline
Member
Joined: Oct 2000
Posts: 5,360
ya,
especially when you have to 'wrong' the last guy.

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