NEC code regarding gfci requirements

[roadrunner255]

Hello all,
Question about requiring gfci outlets in a detached metal building next to my residence.

I have a detached metal building with a 100amp subpanel.

All electrical is thhn 12 guage and 20amp breakers run in emt.

Does the NEC require gfci outlets inside the building and if so what is the code.

All external outlets are gfci and tamper proof.

My electrician said I have a commercial building if that makes a difference.

Cheers

 

[mm08822]

Yes, gfci protection must be provided for all 15/20A receptacles. Either a gfci cb or a gfci receptacle wired for inclusion of downstream recepts will work.

By NEC code, your shed is considered an accessory building as it is on a dwelling property, unless you have it clearly differentiated with the town as a commercial building.

Refer to NEC 210.8(A)(3).

You also need the interior 15/20a recepts tamper-proof. NEC 406.26(1).

 

[roadrunner255]

Thanks. forgot to add all my receptacles are duplex mwbc with a shared neutral (pigtails at the box).

Any code changes that would effect your post prior to 2015?

 

[dave*99]

Thanks. forgot to add all my receptacles are duplex mwbc with a shared neutral (pigtails at the box).

Any code changes that would effect your post prior to 2015?

This needs 2 pole GFCI breakers in the panel due to the shared neutral.

 

[mm08822]

Thanks. forgot to add all my receptacles are duplex mwbc with a shared neutral (pigtails at the box).

Any code changes that would effect your post prior to 2015?

You'll have to find out what code version you were on in your locale at the time of build. Then go to NFPA website and check relevant NEC 70 edition.

MWBC are going to require a gfci recept at each outlet location and not use the feed-through feature on each recept if the neutral is shared down to the last recept in the string.

 

[kngelv]

MWBC's are stupid IMHO. You save a few dollars and introduce more risk. You need either a two pole breaker or two side by side with a handle tie. They have to be on different phases. You need to pay a lot of attention to phasing and balancing loads. Also there are hazards if you drop a neutral to both humans and equipment. Plus it's easy to overload a neutral if you don't do a good job of balancing. Since you have conduit I'd just run another neutral and isolate the circuits. And... yes you need GFCI protection on all the outlets which are easiest to do with a breaker.

James

 

[dave*99]

Plus it's easy to overload a neutral if you don't do a good job of balancing.

Nope. If the MWBC is wired properly, meaning the 2 hots are on opposite legs, the neutral carries the difference current. Therefore it's impossible to overload it.

It's a requirement to pigtail the neutral to help avoid dropping the neutral.

 

[roadrunner255]

I understand MWBC, electrician recommended it and he enforced what happens when you loose a shared neutral, making sure the pigtails and all connections were securley connected and metal boxes grounded and bonded.

Aside note, I noticed Romex NM-B 12-3 is purple now.

Thanks all!

 

[kngelv]

Nope. If the MWBC is wired properly, meaning the 2 hots are on opposite legs, the neutral carries the difference current. Therefore it's impossible to overload it.

It's a requirement to pigtail the neutral to help avoid dropping the neutral.

These are mainly used to save money on wire and box size or maybe in a kitchen to split a receptacle for separate circuits. In a separate building shop it's just dumb. Too many risks and too little reward. I see crappy pigtails quite often and if you drop the neutral then you are looking at voltage bouncing between 0 and 240. Your equipment will love that. Also he is using THHN in conduit. why not just pull the extra neutral?

James

 

[dscheidt]

MWBC's are stupid IMHO. You save a few dollars and introduce more risk. You need either a two pole breaker or two side by side with a handle tie. They have to be on different phases. You need to pay a lot of attention to phasing and balancing loads. Also there are hazards if you drop a neutral to both humans and equipment. Plus it's easy to overload a neutral if you don't do a good job of balancing. Since you have conduit I'd just run another neutral and isolate the circuits. And... yes you need GFCI protection on all the outlets which are easiest to do with a breaker.

If you don't understand how MWBC work, and you clearly don't, you probably shouldn't be using them.

These are mainly used to save money on wire and box size or maybe in a kitchen to split a receptacle for separate circuits. In a separate building shop it's just dumb. Too many risks and too little reward. I see crappy pigtails quite often and if you drop the neutral then you are looking at voltage bouncing between 0 and 240. Your equipment will love that. Also he is using THHN in conduit. why not just pull the extra neutral?

James

Because it increases the wire needed, increases voltage drop, and increases the not just the number of conductors in the conduit, but the number of current carrying conductors, which can require a second conduit run? What’s the downside? Morons can’t work on it?

 

[wyliesdiesels]

MWBC's are stupid IMHO. You save a few dollars and introduce more risk. You need either a two pole breaker or two side by side with a handle tie. They have to be on different phases. You need to pay a lot of attention to phasing and balancing loads. Also there are hazards if you drop a neutral to both humans and equipment. Plus it's easy to overload a neutral if you don't do a good job of balancing. Since you have conduit I'd just run another neutral and isolate the circuits. And... yes you need GFCI protection on all the outlets which are easiest to do with a breaker.

James

since the feeding breaker is double pole, you dont need to pay attention to phasing as you will have both phases. dont have to worry about load balance or overloading the neutral because the neutral only carries the difference in current.

 

[Codyboy]

MWBC's are stupid IMHO. You save a few dollars and introduce more risk. You need either a two pole breaker or two side by side with a handle tie. They have to be on different phases. You need to pay a lot of attention to phasing and balancing loads. Also there are hazards if you drop a neutral to both humans and equipment. Plus it's easy to overload a neutral if you don't do a good job of balancing. Since you have conduit I'd just run another neutral and isolate the circuits. And... yes you need GFCI protection on all the outlets which are easiest to do with a breaker.

James

Lol.
No way to overload the neutral unless you aren't actually making a MWBC and use the same leg. In that case you shouldn't be wiring anything and call an electrician.
I think they're great!
I can wire in a 240v receptacle if I want or need to.
You do realize that the 240v feed coming to your home is a multiwire circuit right?
So basically a MWBC is just an extension of that with a breaker in between.

 

[roadrunner255]

It's looks like the 2020 nec added gfci protection for MWBC. Correct me should I be wrong.

Does the NEC allow in a mwbc to use gfci outlets for protecting outlets down the line using a shared neutral?

For a future project using a mwbr in a duplex outlet,a 2 pole 20a gfci breaker cost of over $100, seems cost effective to use gfci outlets.

Or go back to using 1 pole gfci breaker.

I really like the duplex outlets that use 2 different legs when in the shop using 2 power tools.

 

[dave*99]

Does the NEC allow in a mwbc to use gfci outlets for protecting outlets down the line using a shared neutral?

NEC is irrelevant in this case. You can put GFCI receptacles in every junction box with nothing connected to their load terminals in a MWBC.

You can not connect downstream receptacles that share neutrals to the load terminals. The GFCI receptacle(s) will trip due to the shared neutral connection on their load side.

 

[dave*99]

Or go back to using 1 pole gfci breaker.

How was that connected? If you tie the 2 hot legs together, that works - as it's no longer a MWBC.

 

[roadrunner255]

How was that connected? If you tie the 2 hot legs together, that works - as it's no longer a MWBC.

Sorry I wasn't clear, instead of using a mwbc for quad outlets, use 2, 1 pole gfci circuits for the quad outlets.

What are folks using today for 20a 2 circuit quad outlets?

Looking for a cost effective solution for a future project.

 

[dave*99]

Sorry I wasn't clear, instead of using a mwbc for duplex outlets, use 2, 1 pole gfci circuits for the duplex outlets.

What are folks using today for 20a 2 circuit duplex outlets?

It only works if you use a 2 pole GFCI breaker. That type can deal with the shared neutral. Two single pole units will not work.
Or you have to move away from MWBC and have separate neutrals on your pair of single GFCI breakers.

 

[roadrunner255]

Thanks, I was using duplex when I should have used quad.

 

[mm08822]

If there is no wiring done yet, I would run two separate 12-2's and forget the mwbc. Otherwise, either circuit could trip the 2 pole cb and it may double the places to look for issues. Mute point if all outlets are quads with the 2 same circuits as the outlets are all in the same location.