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Discussion Starter · #1 · (Edited)
Good day,

I am doing some wiring as a homeowner and have a question about sharing neutral lines.

I have attached a diagram for more information.

I would like to put in GFCI breakers to service the exterior outlets of my home and one kitchen outlet. As it is currently wired, the single phase 15A circuit on my panel is run to my kitchen to power one outlet, through the exterior wall to power another outlet, then run to the garage to provide power to the outlets and lights there. From the garage there is also a run of direct burial 14/2 black wire to the septic system. As it is, the circuit is overloaded and I would like to separate the load into two different circuits. The total run is ~100 ft, with ~60 being outdoors.

Proposal:
First circuit 15A GFCI/AFCI breaker -> 14/2 house wire inside -> kitchen outlet -> Exterior house outlet -> junction box -> Shared 12/3 NMWU in conduit -> Garage lights & Septic Pump
Second circuit 20A GFCI/AFCI breaker -> 12/2 house wire inside -> Junction box -> Shared 12/3 NMWU in conduit -> garage outlets.

Sharing the neutral wire across the two circuits for the outside run of 12/3 is the question I really need answered here. Since unlike a normal circuit where all neutrals are fed back to the panel bus bar, the neutrals in these two GFCI circuits are fed back to the breakers and then back to the bus bar. Will the two neutrals on the circuit being tied together for the underground run create a load return imbalance across the two breakers causing them to trip?

If so, do I need to buy two runs of direct burial wire to run through the conduit instead? Or is there another way around this issue?


imgur.com/a/vav3K
 

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NO.
1. You can't share a neutral with a 20 amp and 15 amp circuit. If you share a neutral you must use a double pole GFCI breaker.
2. If you are redoing the kitchen circuit the receptacle has to be separated to current code. Current code is a spit wired 15 amp receptacle or a 20 amp T slot receptacle. Only needs to be GFCI if within 1.5m of sink.
3. Current codes also requires exterior receptacle to be on their own dedicated circuit.
 

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Discussion Starter · #3 ·
NO.
1. You can't share a neutral with a 20 amp and 15 amp circuit. If you share a neutral you must use a double pole GFCI breaker.
2. If you are redoing the kitchen circuit the receptacle has to be separated to current code. Current code is a spit wired 15 amp receptacle or a 20 amp T slot receptacle. Only needs to be GFCI if within 1.5m of sink.
3. Current codes also requires exterior receptacle to be on their own dedicated circuit.
Thank you for the reply, could you expand on some things for me?

What is the problem sharing a 15 and 20A neutral? I am assuming that is the issue is in line as they all get connected to the bus bar on the panel.
What are your suggestions for getting around that? Should I string another 14guage wire through the conduit to serve as a neutral for that circuit? Suggestions appreciated.
The kitchen outlet is within 1.5m and is required to be gfi, but what do you mean by separated? Do you have a code reference that I can read up on? On the diagram I attached it shows that the kitchen receptacle is only a 15A receptacle wI'll be on a 15A gfci circuit. What is the issue there?
What is the code reference for exterior receptacles being on their own circuit? Is that to just isolate for gfi purposes?
Suggestions or more information required please.

Cheers!
 

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What is the problem sharing a 15 and 20A neutral?
You never find a 15/20 double breaker. It is just never done.

Kitchen receptacle need to be on a circuit that only serves the kitchen.

Kitchen counter codes. Rules 26-700, 26-712, 26-722.

26-726 Branch circuits for single dwellings
This Rule applies to branch circuits for single dwellings only as follows:
(a) outdoor receptacles readily accessible from ground level and installed in accordance with Rule 26-714(a) shall be supplied from at least one branch circuit dedicated for those outdoor receptacles


Kitchen receptacle can two type. They can be 15 amp split wired or 20 not split wired. Your existing 15amp receptacle does not meet any of those requirements. Since you are changing it you must bring it up to current code.
 

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Very Stable Genius
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At a glance I saw 3 code violations in that drawing.
Why not do this?
-regular 20A breaker for kitchen GFI using 12/2
-AFCI 15A breaker for outside GFI using 14/2
-regular 15A breaker for remaining loads in out building using 14/2
Keep it simple.
 

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Ever Learning
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At a glance I saw 3 code violations in that drawing.
Why not do this?
-regular 20A breaker for kitchen GFI using 12/2
-AFCI 15A breaker for outside GFI using 14/2
-regular 15A breaker for remaining loads in out building using 14/2
Keep it simple.
I like this - I like simple - it is easier to figure out later should the need arise. I just looked, and you mention you have direct burial cable for the 14/2 run to the garage ... our Canadian experts will have to tell you whether that is allowed ... it isn't allowed here any more.

The way our inspectors work, I'd keep the "regular 15A breaker for remaining loads in out building using 14/2" portion on the existing circuit, as our inspectors allow usage of 'legacy' systems in various ways which I doubt you are allowed.
 

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Electrician
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NO.
1. You can't share a neutral with a 20 amp and 15 amp circuit. If you share a neutral you must use a double pole GFCI breaker.
You have a code reference for that. I do it often in the commercial world, granted everything is at least #12 so no worries of overloading.

I would never do it in a residential setting but am curious if this is against code.
 

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Very Stable Genius
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I like this - I like simple - it is easier to figure out later should the need arise. I just looked, and you mention you have direct burial cable for the 14/2 run to the garage ... our Canadian experts will have to tell you whether that is allowed ... it isn't allowed here any more.

The way our inspectors work, I'd keep the "regular 15A breaker for remaining loads in out building using 14/2" portion on the existing circuit, as our inspectors allow usage of 'legacy' systems in various ways which I doubt you are allowed.
Hey BM,
The op mentioned "14/2 black wire". This is most likely NMWU - non
metallic wet underground. This is allowed to be direct buried. Still a good
idea to reuse this if possible/:thumbsup:
 

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Ever Learning
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Hey BM,
The op mentioned "14/2 black wire". This is most likely NMWU - non
metallic wet underground. This is allowed to be direct buried. Still a good
idea to reuse this if possible/:thumbsup:
I would! just don't have any realistic idea what those of you north of the border are allowed to reuse. They no longer let us install direct buried, nor overhead feeds. So when our legacy systems need repair we are looking at trenches and conduits and conduit fill volumes and run lengths and number of bends to next pull point.

so long as it's still good, I'd reuse it in a heartbeat! qualifies as a legacy system here.

I'm really emphatic about taking stuff that isn't good out of service : I rewired an out-building, and found several bad things: nearly 80% of the outlets had visible over-current damage, the idiot who installed the romex stapled too tight & the wire was pinned beneath the staples rusted to the wall ... I took cable cutters around the bldg and chopped every bit of it into lengths of about 2 feet. I don't want ANYONE for any reason thinking it "looks like a wire" and trying to use it. My inspector just stared at me - probably not used to homeowners having a grasp of the problem and acting on it. LOL Replaced the feed, the panel, and all the wiring except I left the ceiling lights' wires (for the load only - otherwise new 3-way switching replacing old single switch from new panel).
 

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You have a code reference for that. I do it often in the commercial world, granted everything is at least #12 so no worries of overloading.

I would never do it in a residential setting but am curious if this is against code.
I guess you only need double pole breaker if connect to a split receptacle. If you only use one hot and neutral then you are not required to have a simultaneous disconnect. 14-010

However bringing a 14/2 and 12/2 together into one 12/3 I think would violate the parallel conductor rule as you would have 2 neutrals.
 

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Discussion Starter · #11 · (Edited)
You have a code reference for that. I do it often in the commercial world, granted everything is at least #12 so no worries of overloading.

I would never do it in a residential setting but am curious if this is against code.
I guess you only need double pole breaker if connect to a split receptacle. If you only use one hot and neutral then you are not required to have a simultaneous disconnect. 14-010

However bringing a 14/2 and 12/2 together into one 12/3 I think would violate the parallel conductor rule as you would have 2 neutrals.
What is the parallel conductor rule? Was thinking if the problem here is stringing two neutrals, then is there a rule about stringing another neutral wire through the conduit along with the 12/3 wire?

Also ref the 14/2 wire going to the septic from the garage I can't really mess with that as it has to be on all the time running my system.

For the service that is currently installed, there is only a regular 15A circuit breaker feeding 14/2 to the outlet by the sink.
From what you folks have been saying if I swap the outlet for a gfci (does this have to be 20A? And if so why do they sell 15A gfci outlets anymore?), then I can just leave the breaker and wire intact and disconnect the run going to the exterior outlet on the other side of the wall.
If I then run a new 14/2 inside the house to the junction box mounted outside, then I can connect backwards to the exterior outlet (mounted 2.5m above grade) from the junction and forwards to the garage lights and septic pump through the conduit going out to the garage.
The question is though, is it OK to run an additional neutral wire through the conduit beside the 12/3 wire I already have, or do I need to return the 12/3 wire and get 12/2 and 14/2 for the two circuits?


Also I forgot to mention that garage needs to be 20A as table saw draws 15A and overloads 15A circuit (80% of it anyways).
 

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What is the parallel conductor rule?
You are not permitted to parallel conductors of less than 1/0.
By taking the 14/2 and 12/2 and joining them into a multiwire circuit you have paralleled the neutral which is less than 1/0.

12-108 Conductors in parallel (see Appendix B)
(1) Ungrounded and grounded circuit conductors of similar conductivity in sizes No. 1/0 AWG and larger, copper or aluminum, shall be permitted to be installed in parallel
 

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Discussion Starter · #15 ·
Crap... really wish I knew an electrician in Kingston that could stop by the house for a case of beer and walk me/talk me through all the stuff I want to do... or better yet trade me for computer work haha.
 
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