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Fpbaum 04-26-2012 11:49 PM

Replacing kitchen gfci with gfci breakers-something's not right
 
Hi all, this is my first post, so...my kitchen was just renovated and the electrical outlets are on the walls and I wanted them in plugmold under the cabinet. Why didn't it happen? Long story, but I'm doing it myself now. The electrical receptacles are on 2 separate circuits with a gfci receptacle on each and neither circuit has a receptacle outside the kitchen where I can put the gfci's, so I'm putting gfci breakers in the panel instead. I've run into a different problem on each circuit that'd like some advice on.

Circuit 1: this is a 20 amp circuit. I have to plug this circuit's neutral wire into the gfci breaker, but I couldn't see which neutral wire matched the hot wire (buried in mess of wires) and I don't have a continuity tester so I just pulled one neutral at a time (tedious) until the circuit failed, but it never failed. So I did this again for every neutral...same result. This circuit shares a few boxes with other circuits so I'm wondering if the neutrals on different circuits are tied together somewhere, and if so I'm pretty sure, but not completely, that that's not going to work with the gfci breaker. So I didn't install that gfci breaker since I'm not confident it would actually gfci (yep i verbified gfci). What do you think?

Circuit 2: this is a 20 amp circuit. This circuit currently has the refrigerator, gas stove and range hood, and then a gfci in front of 3 electrical receptacles, which already sounds bad since I thought the kitchen receptacles required 2 dedicated circuits. I replaced that breaker with no problem, but it tripped after a few minutes and continued to trip every few minutes. I haven't changed anything else on that circuit yet and it's never tripped before, but now it is, so I put the old breaker back for now. The current gfci receptacle is only protecting the 3 outlets since the appliances are ahead of it. I know you wouldn't normally want the appliances gfci protected, so do you think the refrigerator motor may be a problem? Do I need the appliances on a separate circuit? What would you suggest I do?

Thanks, and if you're wondering "why all the effort?", it's partly because I'm meddlesome, partly because I'm bored, and partly because the backsplash tile is to be on showcase, not the electrical receptacles.

darren 04-27-2012 12:01 AM

Quote:

Originally Posted by Fpbaum (Post 908574)
Circuit 1: this is a 20 amp circuit. I have to plug this circuit's neutral wire into the gfci breaker, but I couldn't see which neutral wire matched the hot wire (buried in mess of wires) and I don't have a continuity tester so I just pulled one neutral at a time (tedious) until the circuit failed, but it never failed.

Are you saying you went into your panel while it was hot and started pulling random neutrals off the neutral bar? If so you have no clue about electrical and should get someone in there to help you. Obviously your computer did not get fried, hopefully nothing else got fried.

Not to get to technical, but when you have a neutral that is shared between two hots and you disconnect that neutral you turn your circuit into a series circuit. In a series circuit the voltage is divided over the loads to equal 240. Depending on the resistance of the loads one thing could see 190V and the item will see 50V. if you were to put 190V to your tv, you would kill your tv.

Never pull a neutral off the neutral bar unless you are positive the hots associate with it are turned off..

k_buz 04-27-2012 12:06 AM

What do you mean that you want the recepts under the cabinet and what do you plan to do with the existing wall recepts/wiring?

joecaption 04-27-2012 12:08 AM

Where do you live. I see no way your trying to do this is going to meet code.
May be why when they were redoing everything it did not get done your way.
http://www.ask-the-electrician.com/k...electrical.htm

k_buz 04-27-2012 12:13 AM

It can very well meet code, but I'm waiting on seeing his plan before making any suggestions.

Fpbaum 04-27-2012 01:02 AM

Wow thanks for the fast responses! I'm humble so if I'm being unsafe or generally an idiot, let me have it.

Darren, I switched the panel off before pulling and testing each, but your warning is still interesting to me. This is a question, not a retort...isn't pulling the neutral functionally the same as turning off the light switch since it opens the circuit? If pulling the neutral created a series 240v circuit, mustn't that neutral have been between the two 120v sources without another voltage drop between them, which sounds like it would have already been a problem?

K_buz, I want the receptacles in plugmold mounted under the cabinets. I'd be moving the receptacles up essentially, each replaced by a 2 or 3 outlets strip, and since the wires are dropped from the attic I should have enough length and I'd just remove the existing receptacles and patch the wall. Because I can't put a gfci into the plugmold and I don't have another place to move the gfci upstream, I figure I need the gfci breaker.

Joecaption, I'm in Houston. While I'm fairly certain that what I want can be code compliant since the electrician and contractor said it was ok, it may take more work than they wanted to do to make it so. Though maybe there's more to it since its not like I was offering glass beads for this request.

Fpbaum 04-27-2012 01:13 AM

Darren, maybe his is what you are warning about?
http://ecmweb.com/mag/electric_multi...anch_circuits/

I hadn't thought about that, still noodling on it.

AllanJ 04-27-2012 06:44 AM

Quote:

Originally Posted by Fpbaum (Post 908603)
Darren, I switched the panel off before pulling and testing each, but your warning is still interesting to me. This is a question, not a retort...isn't pulling the neutral functionally the same as turning off the light switch since it opens the circuit? If pulling the neutral created a series 240v circuit, mustn't that neutral have been between the two 120v sources without another voltage drop between them, which sounds like it would have already been a problem?

request.

For a neutral that serves just one hot wire, unhitching the neutral is functionally the same as turning off a light switch.

When the neutral serves two circuits (typically in a cable with a red and a black hots), then the two circuits (referred to as one multiwire branch circuit) perform properly with 120 volts between either hot and the neutral. For each circuit the current from the hot wire goes through the lights and appliances and returns via the neutral. Assuming the MWBC was connected in the breaker box correctly the return current for one half circuit more or less cancels out the return current for the other half circuit with the net current in the neutral being equal to the difference between the two.

You can think of that portion of the total load equal to the smaller of the total loads on each half circuit is in a 240 volt series circuit. Then the excess load on one side is thought of as served by hot and neutral.

If you unhitch the neutral and it served two circuits then current continues to flow through any lights or appliances still turned on if there is at least one thing turned on for each of the two circuits. The voltage will become unbalanced depending on the resistance of the various lights and appliances on each side. In other words, bad things happen if you disconnect the neutral expecting the difference in return currents for the two half circuits of the MWBC to be absorbed by just the two hot wires. Specifically the number of amperes for the red wire will become the same as the number of amperes for the black hot wire and in addition the red to midpoint (formerly neutral) voltage will become unequal to the black to midpoint voltage depending on the amount of the loads on each side in terms of resistance. At all times between any two points in a circuit voltage equals resistance between those points times amperes flowing between those points.

In addition, if you unhitch the neutral while the breaker is still on, and lights or appliances are still turned on for that circuit, then the neutral wire end you hold in your hand will be hot. You could be electrocuted if the difference in current between the two half circuits of the MWBC was more than a few hundredths of one ampere.

joed 04-27-2012 08:31 AM

#1. You are correct sounds like a neutral cross connection that will need to be fixed for the breaker to work.
#2. One of your appliances that is plugged into the GFCI circuit is faulty. Refrigerator is the likely cause. Try plugging each device into a different circuit with an extension cord until you find the faulty one. Then have it repaired.

AllanJ 04-27-2012 09:19 AM

Do you still have portable lights such as table lamps with incandescent bulbs? Plug a few into different receptacles including the refrigerator receptacle. If you notice unusual dimming or brightening (not just for a second) as the refrigerator kicks on or if you operate a hair dryer from one of those receptacles or a receptacle in the next room then you have a problem or created a problem with the neutral wires.

When you use a GFCI receptacle's load terminals to protect additional receptacles further on, the white (neutral) wire attached to the load side terminal must not be bonded to (interconnected with using any combination of intermediate wires) the neutral connected to the line side terminal.

Fpbaum 04-27-2012 09:18 PM

Allanj and joed, thanks for the suggestions on #2.

Joed, do you have a suggestion for how to track down the neutral cross connection? Initially I took a bad approach.

k_buz 04-27-2012 09:33 PM

There might not be a cross connection...those kitchen circuits...are they on a 3-wire network? If so, you would need to install a 2P GFI breaker.

Fpbaum 04-28-2012 07:59 PM

K_buz, doesn't look like there are any 3 wire cables in the box other than for the AC, heater and dryer circuits. Though there's a white wire taped black on a 15A single pole breaker so maybe someone created their own 3 wire circuit.

a7ecorsair 04-28-2012 09:23 PM

Quote:

Originally Posted by Fpbaum (Post 909753)
K_buz, doesn't look like there are any 3 wire cables in the box other than for the AC, heater and dryer circuits. Though there's a white wire taped black on a 15A single pole breaker so maybe someone created their own 3 wire circuit.

This would indicate one leg of a 240 v circuit. You need to locate the black wire that is paired with this white and understand why it is this way.

Fpbaum 05-01-2012 09:43 AM

Thanks ae7corsair, and thanks all for your help. This weekend I'll be investigating all of this using your suggestions so will likely post back any findings if they don't leave me with a clear path forward.


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