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Old 03-11-2018, 06:58 AM   #1
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Default Hot neutral?

Hello fellows. A couple of questions for you guys. Helping my friend out. He got some wiring issues in his kitchen. First, He has a 12-3 wire going from his panel box to a outlet box on his kitchen counter. The black and red wires are going to separate breakers. The red wire in the outlet box is connected to other wire going down to the dishwasher. The black wire from the panel box is feeding a receptacle and some under counter lights. Both circuits are sharing the white neutral from the panel box. This setup has been working for a while. We ran into a problem when trying to hook up a GFCI outlet in place of the regular receptacle. The GFCI did not like it and wouldn't work.

1) first puzzler. A Bosch high end Dishwasher. I turn the breaker on to the red wire which in turn sends power to the black wire for the dishwasher. With the neutral DISCONNECTED, I can read 120 volts to ground from the white neutral from the dishwasher! When I hook the neutral from the dish to the neutral from the panelbox, I DON'T read any voltage to ground on the neutrals. I don't understand this. Whats going on?

2 )Also, is there something you need to know about sharing neutrals when hooking up GFCI OUTLETS?

Any help and guidance would be greatly appreciated!
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Old 03-11-2018, 07:13 AM   #2
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1) Reeks of a switch leg

2) gfi's don't share noodles well



~CS~
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Old 03-11-2018, 07:20 AM   #3
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Originally Posted by bogart219 View Post

1) first puzzler. A Bosch high end Dishwasher. I turn the breaker on to the red wire which in turn sends power to the black wire for the dishwasher. With the neutral DISCONNECTED, I can read 120 volts to ground from the white neutral from the dishwasher! When I hook the neutral from the dish to the neutral from the panelbox, I DON'T read any voltage to ground on the neutrals. I don't understand this. Whats going on?
Not a puzzler. It's the way things work, because you shut one side of MWBC off, and left the other one turned on, and my guess is you are troubleshooting this with the under cabinets lights on.


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2 )Also, is there something you need to know about sharing neutrals when hooking up GFCI OUTLETS?

Any help and guidance would be greatly appreciated!
You probably hooked it up wrong.
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Old 03-11-2018, 07:40 AM   #4
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I've never had a problem w/ 12-3 MWBC for
kitchen counter top gfci circuits.
I usually do this for the required (2) small
appliance circuits in kitchen. Neutral is shared
on the line side of both gfci circuits.

If you are attempting to share the neutral
on the load side of the gfci , for a different
circuit ,it will trip off every time.

If you are on the load side of the gfci and
attempting to run the dishwasher , maybe
the dishwasher is tripping it off . I never gfci
protect dishwashers.

Last edited by lighterup; 03-11-2018 at 07:42 AM.
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Old 03-11-2018, 08:20 AM   #5
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Originally Posted by bogart219 View Post
1) first puzzler. A Bosch high end Dishwasher. I turn the breaker on to the red wire which in turn sends power to the black wire for the dishwasher. With the neutral DISCONNECTED, I can read 120 volts to ground from the white neutral from the dishwasher! When I hook the neutral from the dish to the neutral from the panelbox, I DON'T read any voltage to ground on the neutrals. I don't understand this. Whats going on?
I hope that high end Bosch dishwasher survives your troubleshooting methods.

Disconnecting a neutral in a MWBC creates a series circuit at 240V. If you have those counter lights running on the other circuit along with the D/W, there is a potential for very bad things to happen. Those counter lights will basically determine the voltage the D/W sees.

Quote:
2 )Also, is there something you need to know about sharing neutrals when hooking up GFCI OUTLETS?
If you share the neutral on the load side of a GFCI with another circuit, it will trip.
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Old 03-11-2018, 08:54 AM   #6
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And this is the reason why the NEC pushes against MWBC.
To keep it simple for the unskilled.
I say let em fry their GFI's and appliances trying to figure it out.
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Old 03-11-2018, 09:05 AM   #7
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Originally Posted by Helmut View Post
Not a puzzler. It's the way things work, because you shut one side of MWBC off, and left the other one turned on, and my guess is you are troubleshooting this with the under cabinets lights on.

You probably hooked it up wrong.
Good Answers
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Old 03-11-2018, 09:15 AM   #8
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First what do you guys mean by MWBC?
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Old 03-11-2018, 09:16 AM   #9
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Not a puzzler. It's the way things work, because you shut one side of MWBC off, and left the other one turned on, and my guess is you are troubleshooting this with the under cabinets lights on.

No


You probably hooked it up wrong.
Yes, that is why on here asking for help!
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Old 03-11-2018, 09:17 AM   #10
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First what do you guys mean by MWBC?
Multi
Wire
Branch
Circuit

That is what is feeding those two circuits.

This is important stuff, and to be honest, you should know this before troubleshooting.
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Old 03-11-2018, 09:18 AM   #11
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First what do you guys mean by MWBC?
Multi-Wire Branch Circuit, two breakers sharing a neutral.
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Old 03-11-2018, 09:57 AM   #12
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First what do you guys mean by MWBC?
Multi Wire Branch Circuit.

That is a super common item on both single and three phase system with neutral conductor in the system.

Anytime you see the MWBC .,, you NEVER ever open the neutral conductor on purpose. you can damage anything on the MWBC.

The voltage will go up or down depending on the type of load it is hooked up on MWBC.
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Old 03-11-2018, 09:59 AM   #13
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Multi-Wire Branch Circuit, two breakers sharing a neutral.
Yup on single phase system and on three phase system you will find three breaker sharing a neutral.
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Old 03-11-2018, 10:24 AM   #14
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Multi-Wire Branch Circuit, two breakers sharing a neutral.
I've seen circuits sharing neutrals before but never seen this acronym before.

So to recap. took one hot and the neutral from the panel box to the dishwasher.
Hooked the black and ground wire to the dishwasher. Left the neutral to the dishwasher from the panel box UNHOOKED. Why am I reading 120 volts to ground on the neutral from the dishwasher?
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Old 03-11-2018, 10:30 AM   #15
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Default Hot neutral?

Quote:
Originally Posted by bogart219 View Post
I've seen circuits sharing neutrals before but never seen this acronym before.

So to recap. took one hot and the neutral from the panel box to the dishwasher.
Hooked the black and ground wire to the dishwasher. Left the neutral to the dishwasher from the panel box UNHOOKED. Why am I reading 120 volts to ground on the neutral from the dishwasher?

Because the neutral is the return path for the current of the dishwasher.

Because the neutral is disconnected, there is now potential (voltage) to complete the circuit.

If you test between the dishwasher neutral and the circuit neutral back to the panel, you should also read 120V.

The ground wire (albeit not correct) and the neutral are potential paths to complete the circuit.

If those counter lights are also on with the other circuit, that is another path. That is where things will start burning up.


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Last edited by Barjack; 03-11-2018 at 10:33 AM.
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Old 03-11-2018, 10:30 AM   #16
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Originally Posted by bogart219 View Post
I've seen circuits sharing neutrals before but never seen this acronym before.

So to recap. took one hot and the neutral from the panel box to the dishwasher.
Hooked the black and ground wire to the dishwasher. Left the neutral to the dishwasher from the panel box UNHOOKED. Why am I reading 120 volts to ground on the neutral from the dishwasher?
That is how electricity works. Your hot is going through something in the dishwasher and coming back on the neutral. You read voltage on the neutral because you disconnected it.

You’ve most likely fried the dishwasher by opening the neutral at the panel. If both circuits were on and if the neutral downstream was still connected to both the under cabinet lights and the dishwasher, opening the neutral at the panel turns your mwbc into a 240volt series circuit.
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Last edited by eddy current; 03-11-2018 at 10:39 AM.
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Old 03-11-2018, 11:20 AM   #17
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That is how electricity works. Your hot is going through something in the dishwasher and coming back on the neutral. You read voltage on the neutral because you disconnected it.

You’ve most likely fried the dishwasher by opening the neutral at the panel. If both circuits were on and if the neutral downstream was still connected to both the under cabinet lights and the dishwasher, opening the neutral at the panel turns your mwbc into a 240volt series circuit.
The dishwasher works fine. Never "opened" the neutral at the panel. Didn't connect it at the outlet box.
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Old 03-11-2018, 11:24 AM   #18
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That is how electricity works. Your hot is going through something in the dishwasher and coming back on the neutral. You read voltage on the neutral because you disconnected it.

You’ve most likely fried the dishwasher by opening the neutral at the panel. If both circuits were on and if the neutral downstream was still connected to both the under cabinet lights and the dishwasher, opening the neutral at the panel turns your mwbc into a 240volt series circuit.
This right here is what I'm trying to get at. Is this normal? How can this be?
Thanks!
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Old 03-11-2018, 11:33 AM   #19
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This right here is what I'm trying to get at. Is this normal? How can this be?
Thanks!
???? Of course it’s normal. Wire a light bulb with a hot and a neutral. Turn it on and then open the neutral. What voltage do you expect to read from the neutral leaving the light back to the source?
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Old 03-11-2018, 12:37 PM   #20
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STOP


Put everything you took apart, back together again, except for the GFI that was the initial problem.

You had to of hooked the GFI up wrong, or have a bad GFI, and now your chasing a dishwasher circuit????

Had did you disconnect the old recep, and how did you hook up the new GFI?
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