Is there a simple way to figure out which is the first recepticle on a
circuit? I have an older house - the two upstairs rooms are on the same
circuit and are not grouned. Id like to add a GFCI plug on the first
recepticle on that circuit, so every recepticle downstream is
The brute force method would be to guess which recepticle is the first,
remove the outgoing wires, and test every other outlet for power -
rinse (hook back up the wires), repeat, until ive found the recepticle
that has power and all the others that dont. :) However this will take
awhile - most arent easily accessible - behind furnitire, beds etc.
I have at my disposal the standard home repair tools - volt meter, etc.
I don't know exactly how to do it in practice, but in theory
Unplug everything on the circuit.
At the circuit breaker box, with the breaker off, connect what would
have been the hot wire of the circuit to the neutral. Leave the neutral
Measure between one slot and the other at each receptacle.
At each receptacle, the measurement of the resistance and inductance
will be different. They will be lowest at the first, and highest at the
14 gauge wire only has a resistance of 2.6 ohms per 1,000 feet, so the
difference in resistance will be difficult to measure. But the
inductance should be substantially different at each receptacle. At
higher frequencies, the measurement should be easy.
Get something that detects AC _current_ in a wire without electrically
connecting to the wire. Perhaps a pick-up coil attached to an amplifier
or perhaps a large coil simply connected to an earphone. I'm not used to
the commercial non-contact detectors, but one of them would work. You
want something that makes a different indication for a current flowing
wire and just a hot wire. After you have your detection tool, experiment
with it. Learn to detect a current-carrying wire.
With the circuit breaker on, plug-in a high-wattage lamp in what you
suspect to be the first receptacle. You should not be able to detect
current moving through the wires at any other receptacle. If you detect
current at a receptacle, it's at a position before the lamp receptacle.
Unplug the lamp and plug it in what you suspect to be the last
receptacle. You should be able to detect current at every receptacle.
Note I'm making a distinction between a receptacle with current going
through the wires connected to it and a receptacle that's just hot. All
of them should be hot. The electromagnetic field will be much stronger
around a current carrying wire.
Get a really high-wattage load, perhaps a big electric heater, something
with a high enough wattage to heat its supply wires detectably - but not
dangerously. Use the same system as the current detector. Plug in the
load at the (believed) last receptacle. Check the earlier receptacles
for warm wires. You get the idea.
Fire the circuit up with DC (use a rectifier by the circuit breaker
box). Put a low-resistance load on the circuit at some receptacle. With
a sensitive voltmeter, measure between a hot slot of one receptacle and
the hot slot of another. The existence and the polarity of this tiny
voltage drop will show the relative position of the receptacles. If you
draw a diagram, you'll understand.
You could do this with the regular AC too, but you wouldn't get the
polarity info. You still could figure out which receptacle is first.
You're testing for a voltage drop across a load, which in this case is
just a piece of wire between receptacles. The voltage drop will not be
from google on GFCI circuit breaker
For broad protection, GFCI circuit breakers may be added in many panels
of older homes to replace ordinary circuit breaker. For homes protected
by fuses, ...
Yea, ive read that page before.
afaik, those breakers are pretty expensive. But ill check today and
possibly pick one up.
Thanks for the comments all. Nehmo - your post alluded to a method I
had considered, but im not skilled enough to know exactly what to do :)
What you say makes sense, but I think ill either go with a breaker, or
the method I talked abut.
Thanks all for comments.
Is there a posibility of sticking a new outlet near the breaker panel?
I've thought about gfci-ing some circuits by doing this:
Install the box/outlet near the main panel.
Unhook the wire from the breaker.
Add a new wire that goes from the breaker to the new (gfci) outlet.
Take the old wire, and feed it from the gfci outlet.
Does anyone know if this is acceptable by NEC code?
I cannot think of a reason that it wouldn't be, but then, I'm no
expert. There might be some "exposed wiring" issues.
If it is allowed, perhaps you could have an electrician do that for
May no harm befall you,
Ich habe keine Ahnung was das bedeutet, oder vielleicht doch?
Yes, it's acceptable, and in fact, it's exactly what many electrical
contractors do to save the customer money when it looks like it will
take a lot of time to find the first outlet, as in this case. In most
cases one only needs to try to visualize what the quickest, easiest,
and most practical way to run the circuit; usually yields a clue as to
where the first outlet is located.
Great idea guys re GFCI right at the panel..
I think I might have to go this route anyway.
Ive done about half the recepticles - Im confused because each
recepticle is at the end of the line - ie wire comes in, but not out.
Becasue of this im guessing that there is a central junction box (es)
in the attic or ceiling with drops down to each recepticle.
As an fyi - there are hardwired ceiling lights on the circuit as well,
although none of the recepticles are switched (they are always live).
Many people have suggested getting in the attic. I'm going to try this,
but its not going to be that easy. My house is a 1.5 story and the
attic is very small - only a couple feet in the best of places, with
lots of fiberglass - so mucking around in there will not be pleasent.
1) If I do as suggested and put the GFCI by the panel - will each
recepticle be covered if its like I describe above? I can visualize
quite easily a series of recepticles with the first being a GFCI and
how they would all be covered. However in my case it seems a bit more
complicated - ie lights, a junction box spreading to each recepticle,
etc. Would this till be ok? Is there any situation where putting a GFCI
as the first recpeticle on a circuit would NOT protect ones downstream?
2) Once Ive hooked up the GFCI, is there any way to CONFIRM each
recepticle is covered? Ie something i can safely do to try and trip the
GFCI (and something safe incase its not on the same circuit as the
GFCI). Hopefully what ive said here makes sense.
Thanks for the responses all, very helfull.
Then you won't be able to install a GFCI receptacle at the first
outlet. Go with the GFCI receptacle at the panel.
Possibly, or you may have knob and tube wiring.
Yes, it will be OK.
Yes if you install the GFCI at the panel.
Yes. The way your house is wired as you described. There's not a
Yes, trip the GFCI and verify that all outlets on that circuit go dead.
You also want to make sure that you do _not_ have a ground connection
between any of the downstream outlets. It's possible that the ground
is hidden or that BX cable was used.
" You also want to make sure that you do _not_ have a ground connection
between any of the downstream outlets. It's possible that the ground
is hidden or that BX cable was used. "
Thanks for your responses Volts500.
It is NOT knob and tube from everything Ive seen so far.
Can you elaborate a little on what you mean by " make sure you do not
have a ground connection between any downstream outlets ".
About half of the outlets have NO ground (not even to the box).
The other half use a newer cable and are grounded to the box. That
ground is connected to the outgoing ground as well which I presume
leads to the next outlet.
However when I test the outlets with a tester, it reads "open ground" -
ie not grounded back to the panel.
Are you saying:
1) Remove the outlet to ground connection for each outlet? Ie dont
hookup a ground to the outlet? If so, what should I do with that ground
wire? Cap it off? Should it be hooked to the junction box?
2) Or something else?
Could you explain why I _dont_ want a ground connection between any of
the downstream outlets?
I think Tom Horne did a good job of explaining the reasons for not
connecting the ground on downstream outlets in a previous thread. In
your case in may be best to use isolated ground receptacles as he
suggested in the "replacing older electrical outlets" thread. You
should be able to find that thread a few pages back in this newsgroup,
or google it. Also, the non-grounded three prong receptacles need to be
marked "no ground" with the stickers that come with the GFCI
receptacle. Also, the instructions that come with the GFCI receptacle
should help a lot.
A GFCI doesn't use ground. It responds to unintended ground
connections (indicated by a difference brethren hot and neutral
currents), like when you touch a defective power tool and become part
of the circuit.
The problem with connecting grounds (when no connection to earth
exists) is not specific to GFCIs. If you have 2 receptacles connected
this way, and an appliance plugged into one has a short from hot to
ground (one that's not quite enough to trip the breaker), the ground
connection at the other receptacle is now hot. You can get
electrocuted by touching what was supposed to be a safety ground.
On 12 Feb 2006 11:55:55 -0800, canadian firstname.lastname@example.org wrote:
Mine are like that. In most cases, wires to each receptacle and switch
come from a junction box at the ceiling light fixture. The whole thing
would look something like a giant octopus on top of the room with
tentacles hanging down all over. In that case, maybe you could put a
GFCI in a box next to the existing ceiling one. The other rooms use
pigtails so each receptacle has it's own connection (no others depend
My attic looks like that.
Something that won't work on shared neutral circuits.
Ground each hot connection, through a resistor (just like the test
buttons do). The resistor limits current in case the GFCI doesn't
[crossposted, s.e.d dropped from followups]
On Sun, 12 Feb 2006 07:38:58 -0800, canadian_woodworker wrote:
Well, as long as I have your attention, it makes absolutely no difference
whatsoever which outlet on a main line has a GFCI - each one only protects
itself and what's plugged into it, and couldn't care less what's happening
[view in fixed font, with wrap off]
. Mains Hot -------+-------------+-------------+
. Mains Neut. -----|--+----------|--+----------|--+
. | | | | | |
. ------ ------ ------
. | GFCI | | GFCI | | GFCI |
. ------ ------ ------
. P.C P.C P.C
Where "P.C" means "Protected Circuit".
What has been suggested, (sorry, don't remember by whom - jalegris?) is to
use a GFCI circuit breaker, which goes on the left:
. Mains Hot --| GFCI |----+-------------+-------------+
. Mains Neut.--| C.B. |----|--+----------|--+----------|--+
. ------- | | | | | |
. Ordinary Ordinary Ordinary
. Outlet Outlet Outlet
That's "on the left" in my attempt at a diagram - in real life, it goes in
the breaker panel.
Or, of course, you could upgrade your wiring - it will increase the resale
value of the house considerably! :-)
Not true. GFCI outlets have a gazinta and a gazouta. Anything
attached to the gazouta side is also protected by the GFCI. The
feed-through is usually rated at 20A, which is likely the same as
the branch circuit. If he can find the first outlet he can protect
the whole circuit with a $10 GFCI outlet, rather than a $25 GFCI
breaker. He won't have to go into the basement (or outside, in my
case) to reset the GFCI either.
It could be a GFCI in the first outlet on the circuit, as well.
In Canada, at least, it CAN make a difference depending on where you
put the GFCI outlet - it has input and output terminals. By connecting
it as the first in a chain you can protect all the other downstream
outlets. That's what the OP is trying to do. Of course, you could put
GFCI's on every outlet, but it's overkill. Or should I say underkill?
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