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#29844 - 09/26/03 02:49 PM dimming lights
drgnz23 Offline
Member
Registered: 02/17/02
Posts: 56
Loc: los angeles
hey guys im new to this web page so go easy on me. Im also kind of new to the electrical field so i would apprecite your knowledge. I have a question? Is it normal for a home (built in the 50's) to have dimming lights when appliances get turned on. For example the washer and dryer will cause the light to dim or when the refrigerator kicks on.Is this a big problem? What causes this and can it be fixed?
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#29845 - 09/26/03 04:30 PM Re: dimming lights
ElectricAL Offline
Member
Registered: 10/10/01
Posts: 597
Loc: Minneapolis, MN USA
This is kind of like trying to count the horse's teeth while sitting at the kitchen table.

The only real way to get a good answer that will serve your immediate need is to have a qualified electrician witness the dimming lights and do some tests. The causes are varied. Some are benign, some are malign. . .so, because of the latter, don't put this off.

The benign cause is voltage drop caused by the resistance in the wires that supply the power and a change in current on those wires caused by the motor start currents, and the human eye's peripheral vision sensing this fluctuation of light.

The potentially disasterous cause is a failing, maybe burning, connection, or an open neutral.

Impossible to tell from here.
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Al Hildenbrand
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#29846 - 09/26/03 10:44 PM Re: dimming lights
Trumpy Offline


Member
Registered: 07/05/02
Posts: 8211
Loc: SI,New Zealand
drgnz23,
Welcome to ECN mate!.
It sounds to me like the mains to the panel are too small to supply the in-rush current of these appliances when they start up, causing the drop in voltage and hence the dimming lights.
I'd advise you to get the size of the service and the sub-circuit wiring checked.
Hope this helps.
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#29847 - 09/27/03 05:40 PM Re: dimming lights
DougW Offline
Member
Registered: 06/08/03
Posts: 1143
Loc: North Chicago, IL
Along the lines of what ElectricAL and Trumy have already said, you might want to investigate if the previous installer/owner "piggybacked" or tied together and neutrals from separate branch circuits.

(Easy way to tell - open the main panel board (breaker/fuse box) - if there are x # of circuits listed (with x# of corresponding fuses or breakers), there should be an equal number of neutrals tied into the neutral bus bar - not x# minus a few)

It's also possible that the newer appliances, while higher efficiency, are operating at a higher amperage than the equipment originally spec'd for the installation... maybe somebody switched a 50a dryer receptacle for the original 30a without re-wiring with larger conductors - that's a research and calculation call, to ensure your conductors are the right capacity.

Good luck!

[This message has been edited by DougW (edited 09-27-2003).]
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#29848 - 09/27/03 05:46 PM Re: dimming lights
iwire Offline
Moderator
Registered: 01/05/03
Posts: 4391
Loc: North Attleboro, MA USA
Doug what if he has a house with some multiwire branch circuits?

In this case he will be short neutrals.
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Bob Badger
Construction & Maintenance Electrician
Massachusetts
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#29849 - 09/28/03 08:42 PM Re: dimming lights
Big Jim Offline
Member
Registered: 07/18/03
Posts: 394
Loc: Denver, CO USA
My 2 cents worth: I'm living in a late 50's house with 125 amp service. Frige, W/D, dishwasher have no noticable effect on the lights but I know exactly when the compressor in the garage starts. Since it is a 7.5 HP, single phase, line start, well I should. I think that dimming under normal household loads is a sign of problems. That is in the vintage of 2 wire romex, no ground, and very moderate electrical loads. Among other things, it is a prime candidate to have a FPE panel which, in itself, could explain the problems. Probably a good idea to have it checked out by somebody familiar with that kind of problem. If you're in the trade, get one of the old hands to show you the basics.
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#29850 - 10/01/03 11:35 AM Re: dimming lights
drgnz23 Offline
Member
Registered: 02/17/02
Posts: 56
Loc: los angeles
thanks for all the info..I went out to the panel which had a 100a 2pole zinco breaker and noticed arcing marks where the breaker clips on to the buss bars could this have any affect on the lights?
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#29851 - 10/01/03 01:38 PM Re: dimming lights
iwire Offline
Moderator
Registered: 01/05/03
Posts: 4391
Loc: North Attleboro, MA USA
Yes it could
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Bob Badger
Construction & Maintenance Electrician
Massachusetts
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#29852 - 10/01/03 01:56 PM Re: dimming lights
DougW Offline
Member
Registered: 06/08/03
Posts: 1143
Loc: North Chicago, IL
Quote:
iwire Yes it could


Understatement of the year


Iwire - didn't go into detail in the interest of KISS - was figuring if there were 15 branch circuits and 5 neutrals it'd be obvious to him... unless he has a whole lot of 220 or >30a's on the board.

Mea culpa.
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#29853 - 10/01/03 02:14 PM Re: dimming lights
ElectricAL Offline
Member
Registered: 10/10/01
Posts: 597
Loc: Minneapolis, MN USA
Again, get some one that is a trained and qualified electrician to come to your location. Don't put this off.
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Al Hildenbrand
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