# Service Call of the Day



## Jupe Blue (Aug 18, 2008)

Customer called wanting saying that her vacuum wasn't working when plugged into 2 receptacles in her family room. It worked fine in any other receptacle in the house.

Sure enough, vacuum turned on and sort of hummed in these two receptacles. 



120v H-N, 120v H-gnd at each receptacle.
56v H-N when under load from the vacuum. 
Vacuum rated @ 11amp. Pulling 2.2 amps when plugged into the suspect receptacles.

Guess what I found to be the problem. It was an new one to me, but I'm sure others have seen it before.


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## HackWork (Oct 2, 2009)

Was it a loose neutral?


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## 480sparky (Sep 20, 2007)

It's on a dimmer.


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## HARRY304E (Sep 15, 2010)

Jupe Blue said:


> Customer called wanting saying that her vacuum wasn't working when plugged into 2 receptacles in her family room. It worked fine in any other receptacle in the house.
> 
> Sure enough, vacuum turned on and sort of hummed in these two receptacles.
> 
> ...


neutral was lose in the recptacle.

Or it was old BX and the white wire fell off and they took a white wire from the silver screw and bonded it to the box that will liven things up..:laughing:


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## Jupe Blue (Aug 18, 2008)

480sparky said:


> It's on a dimmer.


You've seen it before. 

I looked for about 20 minutes for loose wiring when I notice a dimmer way on the other side of the room. The customer says she has lived in the house for 5 years and has never known what that switch controlled. I guess my first clue should have been that there was no overhead light fixture. Sometimes you miss the obvious stuff.

The receptacles were wired with only a black and white, not wired for a half switched receptacle with a third conductor.


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## 3xdad (Jan 25, 2011)

Nice 480.:thumbsup:

New variable speed vacuum, for those times when you need it to suck less.


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## Big John (May 23, 2010)

A dimmer will put out full line voltage when there's no load on it...? :confused1: Didn't know that. 

-John


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## Jupe Blue (Aug 18, 2008)

Big John said:


> A dimmer will put out full line voltage when there's no load on it...? :confused1: Didn't know that.
> 
> -John


I think the dimmer was in the on position and fully on when I took the initial voltage reading at the receptacle. When I pulled the receptacle and turned on the vacuum, the readings dropped to the lower voltage.


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## millelec (Nov 20, 2010)

depending on the dimmer, no current flow thru the potentiometer means no voltage drop, so you'll read line voltage at no load.


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## electricmanscott (Feb 11, 2010)

Jupe Blue said:


> Customer called wanting saying that her vacuum wasn't working when plugged into 2 receptacles in her family room..


Did you let her say it? :laughing:


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## erics37 (May 7, 2009)

I had one a while back where the homeowner couldn't figure out why the top half of all the plugs in his living room worked but the bottom half didn't.

I'm sure you can guess what the problem was and how long it took me to figure it out.



One-hour minimum charge please!


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## kaboler (Dec 1, 2010)

erics37 said:


> I had one a while back where the homeowner couldn't figure out why the top half of all the plugs in his living room worked but the bottom half didn't.
> 
> I'm sure you can guess what the problem was and how long it took me to figure it out.
> 
> ...


Were all the receptacles split?


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## HackWork (Oct 2, 2009)

kaboler said:


> Were all the receptacles split?


Yes, but his point was that the light switch was turned off.


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## davis9 (Mar 21, 2009)

Something similar happened to me not too long ago. Swapping some Par Floods on the exterior of a rental property with some 120v 70w HPS fixtures. Turn circuit on and fixture lights momentarily and shuts off, took me 45 mins to locate the rotary dimmer on the side of a joist located in a basement full of garbage. Was reading a clean 120+-V no load.

Tom


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## kbsparky (Sep 20, 2007)

Big John said:


> A dimmer will put out full line voltage when there's no load on it...? :confused1: Didn't know that.
> 
> -John


Most dimmers cut out portions of the sine wave ... meaning the peak voltage is the same, while the average voltage drops. 

Measuring the output voltage with no load won't show much difference, since the peaks are still present.


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## Big John (May 23, 2010)

kbsparky said:


> Most dimmers cut out portions of the sine wave ... meaning the peak voltage is the same, while the average voltage drops.
> 
> Measuring the output voltage with no load won't show much difference, since the peaks are still present.


I guess I wouldn't expect the waveform to change shape when the load is connected.

If dimmers are PWM type, then the amount the dimmer clips off the sine wave is going to be missing regardless of whether it's hooked to anything, right? :confused1:

Unless like _millelec _said, it has something to do with the voltage drop, I can't figure it.

-John


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## nrp3 (Jan 24, 2009)

Would you notice a difference testing with a wiggy vs multimeter at no load?


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## HugoStiglitz (Apr 11, 2011)

nrp3 said:


> Would you notice a difference testing with a wiggy vs multimeter at no load?


I'm going to go out on a limb and say yes since a wiggy would put 'some' load on the circuit.


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## davis9 (Mar 21, 2009)

If the "load" of the wiggy is less than the ampacity/rating of the dimmer would probably be fine. vacuum would cause havoc. Or in my case 2 70w HPS and a few par 90W floods.

Tom


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## nrp3 (Jan 24, 2009)

I have had people ask for a dimmer for a receptacle and always said no for this reason. Thanks for sharing this.


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## davis9 (Mar 21, 2009)

nrp3 said:


> I have had people ask for a dimmer for a receptacle and always said no for this reason. Thanks for sharing this.


It is against code as well.

2011 NEC 404.14(E)

Tom:thumbsup:


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## nrp3 (Jan 24, 2009)

Has it always been against code or is that a new thing?


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## davis9 (Mar 21, 2009)

Not new for 2011, I seem to recall it in the '99 version as well. Could be wrong though.

Tom


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## nrp3 (Jan 24, 2009)

Found it in the 05, same number.


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## crosport (Apr 4, 2010)

If it wasn't for dumbasses putting a dimmer on a receptacle to begin with we would'nt need some stupid rule telling us not to.Imagine what it would do to your flatscreen or other electronics whem dimmer is on part way.


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## GDK 13 (Oct 6, 2009)

nrp3 said:


> I have had people ask for a dimmer for a receptacle and always said no for this reason. Thanks for sharing this.


Sell them this product:

http://files.lutron.com/hwi/TRG/366-963h_components_dimming_receptacles.pdf


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## frenchelectrican (Mar 15, 2007)

davis9 said:


> Not new for 2011, I seem to recall it in the '99 version as well. Could be wrong though.
> 
> Tom


It do go back further than '99 verison I know I did recall it did mention in '84 NEC.

Merci,
Marc


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## HARRY304E (Sep 15, 2010)

davis9 said:


> It is against code as well.
> 
> 2011 NEC 404.14(E)
> 
> Tom:thumbsup:


*Here it is...:thumbsup:*



> *2011 NEC 404.14(E)*
> 
> *(E) Dimmer Switches. *
> 
> ...


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## frenchelectrican (Mar 15, 2007)

Harry and 480.,

I know you been in the trade little longer than I am however do you recall how far did the NEC mention on the dimmer not allowed to be used on the standard receptale ?

I know in ECF { French electrical code } it was written way back 1964. { I have to ask one of my frenid that one. }

Merci,
Marc


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## davis9 (Mar 21, 2009)

HARRY304E said:


> *Here it is...:thumbsup:*


Thanks for posting the whole thing. I had to do it the old way and open a book.

Tom:thumbup:


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## Chris1971 (Dec 27, 2010)

kaboler said:


> Were all the receptacles split?


I'll tell you but, it's a one hour minimum.:thumbsup:


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## Mr Rewire (Jan 15, 2011)

frenchelectrican said:


> Harry and 480.,
> 
> I know you been in the trade little longer than I am however do you recall how far did the NEC mention on the dimmer not allowed to be used on the standard receptale ?
> 
> ...


 I have an old 93 book and i see no mention in it. 380.14


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## DCAC (Feb 11, 2011)

I think lutron sells a outlet dimmer combo that is permited. The outlet has a hump between the H & N, the set comes with a plug that matches the outlet. It prevents anything other than the matching plug from being pluged into those outlets


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## retiredsparktech (Mar 8, 2011)

crosport said:


> If it wasn't for dumbasses putting a dimmer on a receptacle to begin with we would'nt need some stupid rule telling us not to.Imagine what it would do to your flatscreen or other electronics whem dimmer is on part way.


 It wouldn't hurt the newer electronics, as they have switching power supplies in them.


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## crosport (Apr 4, 2010)

retiredsparktech said:


> It wouldn't hurt the newer electronics, as they have switching power supplies in them.


 Yeah that is true,but new stuff or old,things still are prone to damage from dirty or insufficient power sources.Would you hook up your electronics to a dimmer?


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