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#29844 - 09/26/03 05:49 PM dimming lights  
drgnz23  Offline
Member
Joined: Feb 2002
Posts: 56
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?


Work Gear for Electricians and the Trades

#29845 - 09/26/03 07:30 PM Re: dimming lights  
ElectricAL  Offline
Member
Joined: Oct 2001
Posts: 597
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.


Al Hildenbrand

#29846 - 09/27/03 01:44 AM Re: dimming lights  
Trumpy  Offline


Member
Joined: Jul 2002
Posts: 8,211
SI,New Zealand
drgnz23,
Welcome to ECN mate!. [Linked Image]
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. [Linked Image]


Let's face it, these days if you're not young, you're old - Red Green grin

#29847 - 09/27/03 08:40 PM Re: dimming lights  
DougW  Offline
Member
Joined: Jun 2003
Posts: 1,143
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).]


#29848 - 09/27/03 08:46 PM Re: dimming lights  
iwire  Offline
Moderator
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
Doug what if he has a house with some multiwire branch circuits?

In this case he will be short neutrals.


Bob Badger
Construction & Maintenance Electrician
Massachusetts

#29849 - 09/28/03 11:42 PM Re: dimming lights  
Big Jim  Offline
Member
Joined: Jul 2003
Posts: 394
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.


#29850 - 10/01/03 02:35 PM Re: dimming lights  
drgnz23  Offline
Member
Joined: Feb 2002
Posts: 56
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?


#29851 - 10/01/03 04:38 PM Re: dimming lights  
iwire  Offline
Moderator
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
Yes it could


Bob Badger
Construction & Maintenance Electrician
Massachusetts

#29852 - 10/01/03 04:56 PM Re: dimming lights  
DougW  Offline
Member
Joined: Jun 2003
Posts: 1,143
North Chicago, IL
Quote
iwire Yes it could


Understatement of the year [Linked Image]


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.


#29853 - 10/01/03 05:14 PM Re: dimming lights  
ElectricAL  Offline
Member
Joined: Oct 2001
Posts: 597
Minneapolis, MN USA
Again, get some one that is a trained and qualified electrician to come to your location. Don't put this off.


Al Hildenbrand

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