# new light/switch off existing circuit



## gadus (Sep 21, 2012)

I want to wire a light for new basement bathroom, with switch. Utilizing existing circuits, is it simply a matter of jumping a wire from the closest junction box, first to a switch and then to the (new) light?

Also, to wire an outlet for the vanity, can I simply find a close outlet and run a wire from it? 

Thanks much.


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## kok328 (Sep 21, 2012)

for the light, yes it is pretty straight forward.
for the outlet, you will want to pay attention to current load of the circuit you tap into and be sure to install a GFIC outlet.
Better if you can run a dedicated circuit for the outlet as bathroom outlets tend to be used with hair dryers, curling irons and other high wattage items.


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## JoeD (Sep 21, 2012)

You didn't post a location. In the USA under NEC a receptacle in a bathroom MUST be on a 20 amp circuit dedicated to the bathroom only. You can not tap off a nearby circuit for the receptacle. Tapping a nearby circuit is fine for the light fixture is fine or it can be added to the 20 amp bathroom circuit.

In Canada you would be fine tapping any circuit for the light and receptacle as long as the count of outlets(lights, receptacles, fans, etc.) does not go over 12. Only 12 outlets are permitted per circuit.


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## CallMeVilla (Sep 22, 2012)

Practically speaking, what you want to do will "work."  However, if you run a new receptacle it MUST have a GFCI on it AND there cannot be another GFCI on the same circuit or you will get a conflict.  Make sure the circuit is 20A.  Laso make sure the total number of devices on that circuit does not exceed the maximum.   Do not tie a bathroom receptacle to your lighting circuit because your blowdryer will dim the lights.


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## Wuzzat? (Sep 22, 2012)

CallMeVilla said:


> . . .your blowdryer will dim the lights.


So will a laser printer on the same circuit.  It causes a 5v to 8v drop in your nominal line voltage.


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## JoeD (Sep 23, 2012)

CallMeVilla said:


> Practically speaking, what you want to do will "work."  However, if you run a new receptacle it MUST have a GFCI on it AND there cannot be another GFCI on the same circuit or you will get a conflict.



Where did you get this idea? It not true.


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## CallMeVilla (Sep 24, 2012)

Maybe my phrasing was not clear.  You MUST have GFCI protection for bathroom receptacles.  I have seen GFCI's in-line and at the termination point  . . .  but two GFCIs on the same circuit run will cause conflicting trips.

Does that make my point better?  Hope so.


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## nealtw (Sep 24, 2012)

I tiled a backspash and all outlets in the kitchen were on the same cercuit and all had a gfi. I asked why as one would do. He had something faulting sometimes and couldn't figure what or why. He said they did not interfer with each other.


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## gadus (Sep 24, 2012)

Wondering if you guys can help me again...

I home-runned the line for the toilet pump as well as the light in the bathroom. The existing 20 amp breaker (Siemens) was badly corroded so I replaced it but still got some sparking after replacing. The poles (?) are badly pitted and it looks like someone sprayed gray Rustoleum on that area maybe to stave off corrosion. Honestly I looked at the other poles (not all) and there doesn't seem to be anywhere near  the corrosion that there is on the upper two poles (powering 4 breakers in total). I sanded both poles with some 220 I found lying around and it seemed to help a bit but ultimately the sparking on the one breaker returned so I secured it. How should I proceed from here, short of replacing the whole panel? Can I replace just the strip? Thanks again...G.


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## JoeD (Sep 24, 2012)

Are there still empty slots in the panel? Move those breakers to the empty slots if there are and put blanks over the holes. Replace the panel when you can because the bus bars once damaged can not be repaired. 
I doubt you could find the bus bars to replace them unless the panel is still made. Then it would probably be cheaper to buy a new panel and pull the bars out for your panel.


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## Wuzzat? (Sep 24, 2012)

CallMeVilla said:


> two GFCIs on the same circuit run will cause conflicting trips.


The one with the more sensitive trip curve at the value of the leakage current will trip first and make troubleshooting confusing.
That is, which one trips first may depend on how many mAs of leakage you have.

BTW, the trip curve given by UL's 943 standard is a max value and seems to say that almost everyone can stand 20 mA through their body for one second without harm.


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## nealtw (Sep 24, 2012)

GfI are great if you short power to ground but if you touch white and black you are getting plenty and the gfi does not trip. Bin there done that


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## Wuzzat? (Sep 24, 2012)

Building a GFCI that can tell when a person is across the line may be more difficult than building a reliable AFCI.


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## nealtw (Sep 24, 2012)

The part I don't understand is you can still buy things with a two prong plug and with plastic plumbing the sink is not grounded so if you drop that aplience in the sink, it will trip the breaker but not as fast as gfi but the gfi will not trip.


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## Wuzzat? (Sep 25, 2012)

nealtw said:


> The part I don't understand is you can still buy things with a two prong plug and with plastic plumbing the sink is not grounded so if you drop that aplience in the sink, it will trip the breaker but not as fast as gfi but the gfi will not trip.


When I put a hand mixer held by the cord into the water in a grounded concrete basement sink it didn't trip the breaker.  The mixer just slowed way down because the motor cooling propeller now had to push water around instead of air so the current draw must have gone up to almost a stall current value but not enough to trip the breaker.

If that mixer were on a GFCI circuit I guess it would have tripped it, *but not if* all the current coming in the hot line went back out the neutral line.  The closer the mixer is to the sink drain, the more current the drain would divert from the neutral line.
A GFCI is looking for an imbalance in what goes out and what comes back and it assumes the difference it sees is due to somebody being grounded and getting a shock.
It's a differential milliammeter with a go/no-go, trip/no-trip, time-delay output, with a higher differential current giving a shorter trip time.


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## nealtw (Sep 25, 2012)

That could have been a shocking experience.


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## Wuzzat? (Sep 26, 2012)

Yeah, I should have hired a stunt double to do it.  Or an ex-wife.

The best shock I ever got was while standing barefoot on a concrete floor trying to force a four prong auto radio vibrator into a four prong tube socket from an ancient radio set.  It was probably hundreds of DC volts and many mA.  

And the kid standing next to me couldn't imagine what all the fuss was about.


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## nealtw (Sep 26, 2012)

Don't drop a concrete vibrator in the water and then think you can go pick it up.


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## Wuzzat? (Sep 27, 2012)

nealtw said:


> Don't drop a concrete vibrator in the water and then think you can go pick it up.


I guess grabbing it is the easy part.


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