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Old 01-29-2010, 11:48 PM   #1
koz
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What is the easiest way to find the start of a circuit?


Hi Folks,

I want to add GFCI protection to several rooms of my house so that I can add three prong outlets (I have ungrounded wiring in my home).

What is the easiest way to find the start of a circuit in a room? My plan is to assume that the rooms are all wired in such a way that the first outlet in the room would be the one closest to the panel.

I then intend to turn off the breaker, remove that outlet, turn the breaker back on, and then see if the rest of the outlets in the room are dead. If they aren't then I plan on going to the next outlet and repeating.

This feels like it's going to take a very long time, anyone have any tricks for doing this faster?

Thanks!

Jon

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Old 01-30-2010, 06:01 AM   #2
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What is the easiest way to find the start of a circuit?


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Originally Posted by koz View Post
Hi Folks,

I want to add GFCI protection to several rooms of my house so that I can add three prong outlets (I have ungrounded wiring in my home).

What is the easiest way to find the start of a circuit in a room? My plan is to assume that the rooms are all wired in such a way that the first outlet in the room would be the one closest to the panel.

I then intend to turn off the breaker, remove that outlet, turn the breaker back on, and then see if the rest of the outlets in the room are dead. If they aren't then I plan on going to the next outlet and repeating.

This feels like it's going to take a very long time, anyone have any tricks for doing this faster?

Thanks!

Jon
Use GFCI breakers.
As well as being much faster, it can be difficult to get a GFCI receptacle into those undersized boxes.

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Old 01-30-2010, 08:35 AM   #3
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What is the easiest way to find the start of a circuit?


As long as they are not multiwire branch circuits(2 hots shareing a neutral) put your first GFI plug at the panel.

If it is a multiwire branch circuit then you will have to trace out the circuit and see whats on it and do as you were saying. If you can follow the wires from the panel you can usually get a good guess on your first one.
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Old 01-30-2010, 12:03 PM   #4
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What is the easiest way to find the start of a circuit?


Your plan to try to find the head of the circuit may work, or work in some cases. Worth a try. Typically i don't care for GFCI circuit breakers, however this senario may be a candidate for them.
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Old 01-30-2010, 12:11 PM   #5
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What is the easiest way to find the start of a circuit?


You sort of need to be a "detective" and look for "clues"!

One way is to think like the construction worker who ran the wires. Usually they will run the first wire from the breaker panel to the closest outlet. Then from there to the next. So how would the wires be run from the panel to those outlets? And which would be closest in that line to the breaker panel?

Another is to look in the attic and see how wires are run.

Or to look in the basement / crawl space and see how wires are run.

Or test using your method at the extreme ends of walls.

Another way is that wiring has "resistance". This can be measured with a "ohm meter" (Multimeter). You could unplug everything from the circuit. Turn off all light switches. Then turn off the breaker for the circuit. Connect a long wire (cheap speaker wire or whatever) to a ground on the breaker panel. (Screw or whatever). Run the other end of that wire into the room. Then measure the ohms at various outlets at the ground connections to the end of the wire. The lowest ohms reading will be closest to the panel.

There are exceptions to all the above. The wiring might not be in a straight line, but more like a "T" and connected in the middle. Or there may be a ground loop - a junction box which has splices to other grounds (try the neutral wire in this case).
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Old 01-30-2010, 12:19 PM   #6
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What is the easiest way to find the start of a circuit?


P.S. If your name is Bill Gates and money is no object, you could use a Time-domain reflectometer. (Fancy wire length testing tool which costs a young fortune.)

http://en.wikipedia.org/wiki/Time-domain_reflectometer

Megger CFL501F Time Domain Reflectometer,Range 10,000Ft...
http://www.grainger.com/Grainger/items/2WCE3?Pid=search
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Old 01-30-2010, 12:59 PM   #7
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What is the easiest way to find the start of a circuit?


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Originally Posted by Billy_Bob View Post
You sort of need to be a "detective" and look for "clues"!

One way is to think like the construction worker who ran the wires. Usually they will run the first wire from the breaker panel to the closest outlet. Then from there to the next. So how would the wires be run from the panel to those outlets? And which would be closest in that line to the breaker panel?

Another is to look in the attic and see how wires are run.

Or to look in the basement / crawl space and see how wires are run.

Or test using your method at the extreme ends of walls.

Another way is that wiring has "resistance". This can be measured with a "ohm meter" (Multimeter). You could unplug everything from the circuit. Turn off all light switches. Then turn off the breaker for the circuit. Connect a long wire (cheap speaker wire or whatever) to a ground on the breaker panel. (Screw or whatever). Run the other end of that wire into the room. Then measure the ohms at various outlets at the ground connections to the end of the wire. The lowest ohms reading will be closest to the panel.

There are exceptions to all the above. The wiring might not be in a straight line, but more like a "T" and connected in the middle. Or there may be a ground loop - a junction box which has splices to other grounds (try the neutral wire in this case).

Yeah this is a good way. Once you suspect you found a potential outlet remove the plate and see if it has 2 sets of wires, then shut off the breaker and then test the plug to make sure it is in fact the right breaker, then remove the wires and just let them loose, not touching anything. If you have kids or pets that might go there then cap them off and reinsert in the box, then turn the breaker back on and all the other outlets should not work. If some outlets work but some don't then you only broke part of the chain, so try the same thing on one of the working outlets.

Once you found the outlet now you need to make sure you know which two wires are the load and which are the actual power from the panel, you could just leave them loose turn the breaker back on then test to see which two have power.

Some circuits sometimes have other stuff like lights mixed on them which might make this a bit more interesting.

I was looking at GFCI breakers and they are ridiculously expensive, so it's best to just use a receptacle.
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Old 01-31-2010, 07:40 AM   #8
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What is the easiest way to find the start of a circuit?


Quote:
Originally Posted by vsheetz View Post
Typically i don't care for GFCI circuit breakers, however this senario may be a candidate for them.
Quote:
Originally Posted by Red Squirrel View Post
I was looking at GFCI breakers and they are ridiculously expensive, so it's best to just use a receptacle.
GFCI breakers are typically only available as (1") full-size, so they will fill a load center faster than (1/2") half-size breakers. Aside from size and cost, any other reasons to use a GFCI receptacle rather than a breaker?
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Old 01-31-2010, 11:03 AM   #9
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What is the easiest way to find the start of a circuit?


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...Aside from size and cost, any other reasons to use a GFCI receptacle rather than a breaker?
Yes. For something like a garage, people typically never park a car in there, but instead fill it to the rafters with junk!

So the GFCI pops, and it's behind a box somewhere. Might be easier to find a GFCI breaker!

Same with outside outlets. The GFCI might be at the front of the house, but you are using an outlet at the rear of the house, then need to go "hunting" for the GFCI if it trips. I installed separate GFCIs at each outside outlet in my case. These tend to pop quite a bit, so I can reset it there where I am working. And I don't use the "load" connections on these to go to the next outlet. Rather the line sides are all in parallel with pig tails or with the use of junction boxes in the attic.

But with a kitchen and bathroom, the outlets are right there, so easy to find and more convenient to reset the outlet in that case than hunting for the breaker panel.
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Old 02-05-2010, 12:04 AM   #10
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What is the easiest way to find the start of a circuit?


Just to follow up. I found the easiest way to do it is to turn off the breaker then unscrew every outlet on the circuit so I have the wires dangling. Then, turn the circuit back on. I then used a non-contact votage detector to see which wires were still powered. Once I find the hot wire, I put the GFCI on that.

Thanks for all of the help everyone!

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