What did i do wrong? - Outlet install trips breaker

nymex · 10-11-2008, 03:51 PM

Hi there

i'm hoping someone can give me some insight as to what i did wrong when i tried to install a new outlet in my condo. The current outlets are dated so i went to HD and grabbed some new ones: 2-pole 3-wire Grounding Outlet
Rated: 15A - 125V

When i pulled out the old outlet (which according to the stamping is also rated 15a - 125v) I noted the current configuration:
On the hot side: Red in the top, Black on the bottom
White side: 1 White Wire
Grounded with bare copper.

This outlet was backwired.

At first i used the side screws to install the new outlet. After installing it i plugged in a lamp and flipped the breaker. Well the light turned on but so too did sparks fly (it was actually moderately impressive - probably a sign that i over stepped my electrical ambtions) and the main breaker flipped. The unfortunate matter of the situation is that our main breaker is in an electrical room to which only a few have keys.. making it extremely difficult to gain access and reset it (we actually spent a night without power).

Anyways, i removed the outlet that i had initially installed - stripped the wire to about 5/8" and back wired a new outlet flipped the breaker again and it died.

I pulled out another outlet in the same location to verify the wiring and it was done the same..

Can anyone provide any insight as to what went wrong? i though perhaps it was the wrong guage or whatnot but having confirmed the previous rating of the old outlets i dont know what to do - short of calling someone and paying them a couple hundred dollars to laugh at me.

Any ideas will be appreaciated and rewarded with a

EDIT: I was just looking at the old outlet and it looks like the breakoff fin was removed from the hotside - Could this be what was giving me the trouble?

InPhase277 · 10-11-2008, 04:07 PM

Quote:

Originally Posted by nymex

EDIT: I was just looking at the old outlet and it looks like the breakoff fin was removed from the hotside - Could this be what was giving me the trouble?

Yes, it is likely that each half of the receptacle is on a different circuit. The tab separates the two. Break the tab off of the hot side, but leave it in place of the white side. It would be nice if you could get both these circuits on one double pole breaker too...

joed · 10-11-2008, 06:45 PM

Is the receptacle protected by a double pole breaker? That would confirm the split receptacle.
The problem could also be a bunch of half switched receptacles and you have a miswired a switch loop. Were the previous receptacles partially controlled by a switch?

rgsgww · 10-12-2008, 01:09 AM

Basically, there's a tab in between the two brass terminals, break it off and you should be good.

If you break the white one...

This must be what we call a "multiwire circuit" where you have 2 hots (black&red) in the system sharing a neutral (white), if the hots somehow touch each other, then theres a short circuit.

dc4nomore · 10-12-2008, 01:28 AM

I know a split circuit is normal but is it possible for the two hot screws to arc to each other? I mean, they are pretty darn close...

InPhase277 · 10-12-2008, 02:18 AM

Quote:

Originally Posted by dc4nomore

I know a split circuit is normal but is it possible for the two hot screws to arc to each other? I mean, they are pretty darn close...

Not at that 240 V. A higher voltage pulse could get the arc started, but I doubt it would maintain itself once the voltage returned to normal. Air just has too much resistance.

rgsgww · 10-12-2008, 03:01 AM

Quote:

Originally Posted by dc4nomore

I know a split circuit is normal but is it possible for the two hot screws to arc to each other? I mean, they are pretty darn close...

No, not close, you would need alot of voltage, air has alot of resistance, depending on the current, you may need a few kvs to get it started.

dc4nomore · 10-12-2008, 11:17 AM

Quote:

Originally Posted by InPhase277

Not at that 240 V. A higher voltage pulse could get the arc started, but I doubt it would maintain itself once the voltage returned to normal. Air just has too much resistance.

Wait, 240v? Is this because you are using a double pole breaker? So then how is it possible to wire a separate 15 or 20 amp circuit for each screw on the receptacle when they are getting 240v? I thought those are supposed to be 120v circuits...Am I seeing this correctly?

InPhase277 · 10-12-2008, 11:39 AM

Quote:

Originally Posted by dc4nomore

Wait, 240v? Is this because you are using a double pole breaker? So then how is it possible to wire a separate 15 or 20 amp circuit for each screw on the receptacle when they are getting 240v? I thought those are supposed to be 120v circuits...Am I seeing this correctly?

It is two 120 V circuits, sharing a neutral. Between the two hots will be 240 V. If you break the tab off the hot side of the receptacle, then you can wire each half of thye receptacle to a different circuit.

dc4nomore · 10-12-2008, 12:07 PM

Quote:

Originally Posted by InPhase277

It is two 120 V circuits, sharing a neutral. Between the two hots will be 240 V. If you break the tab off the hot side of the receptacle, then you can wire each half of the receptacle to a different circuit.

Oh ok, so if you left the tab on, you would have a 240v circuit. You can have that for some 20A circuits, right?

InPhase277 · 10-12-2008, 01:04 PM

Quote:

Originally Posted by dc4nomore

Oh ok, so if you left the tab on, you would have a 240v circuit. You can have that for some 20A circuits, right?

Not exactly. If you left the tab on, you'd have a 240 V short, which is probably what the OP had. What you have with a split wired receptacle is two 120 V circuits, and we call it a "multiwire branch circuit".

And 240 V circuits come in flavors of 15 A and up, depending on the equipment that needs the power.

dc4nomore · 10-12-2008, 06:27 PM

Quote:

Originally Posted by InPhase277

Not exactly. If you left the tab on, you'd have a 240 V short. And 240 V circuits come in flavors of 15 A and up, depending on the equipment that needs the power.

So then how would you wire up a 240v 15 or 20A circuit? Do you need a special receptacle designed to take two hots, kind of like a range or dryer receptacle?

skymaster · 10-12-2008, 06:47 PM

Yes. Different plugs and recepts

dc4nomore · 10-12-2008, 07:31 PM

Quote:

Originally Posted by skymaster

Yes. Different plugs and recepts

Ok, thanks!

InPhase277 · 10-12-2008, 08:26 PM

Quote:

Originally Posted by dc4nomore

So then how would you wire up a 240v 15 or 20A circuit? Do you need a special receptacle designed to take two hots, kind of like a range or dryer receptacle?

Take a look at this.