Alternatives for AFCI for a 15/20 MWBC (Multi-wire Branch Circuit)

[brycenesbitt]

We've got a building with asymmetric MBWCs.
One leg is 15 amps, the other 20 amps.
They presently use a handle tied Federal Pioneer Electric company 240 volt breaker.

A local gas company's gas separation rule means we have to re-feed the branch circuits to a new location more than 6 wire feet away.

The NEC then triggers an AFCI (and GFCI) requirement.
But we can't find a tandem 15/20 AFCI breaker or combination breaker.
Needless to say, but with a shared neutral circuit on an AFCI that neutral is going to have to land on the breaker for sure.

What are the options here? Putting an AFCI at the first receptacle is the best we've got so far, and we're not sure the AHJ will approve that.

 

[wwhitney]

Needless to say, but with a shared neutral circuit on an AFCI that neutral is going to have to land on the breaker for sure.

With at least 3 brands, that is not the case any more. See

Multi-wire branch circuit

Existing kitchen has a 12-3 to the fridge and kitchen outlets. This county is on the 2023 code. Older GE panel. What if any options are there to bring it up to code. Nobody seems to make a dual function double pole and can’t put a gfci outlet behind the fridge. Is there a way to get arc and gfi...

forums.mikeholt.com

Cheers, Wayne

 

[ramsy]

With at least 3 brands, that is not the case any more.

No FAU in dedicated equipment space, in garage, attic, or outside, appears in 210.12(B).

 

[brycenesbitt]

No FAU in dedicated equipment space, in garage, attic, or outside, appears in 210.12(B).

This is not a dormitory, these are regular apartment homes. Just small ones (no AC, all gas appliances).

 

[Master Nater]

is there any reason you cannot simply take the 20a circuit down to 15, and put them both on a 15a 2p afci?

 

[ramsy]

This is not a dormitory, these are regular apartment homes. Just small ones (no AC, all gas appliances).

2023 NEC 210.12(B) is locations required, not dorms

 

[curt swartz]

is there any reason you cannot simply take the 20a circuit down to 15, and put them both on a 15a 2p afci?

But why reduce the circuit when they can use 2 single pole Siemens PON, Easton BR or GE/ABB THQL with handle ties?

 

[pipe_bender]

We've got a building with asymmetric MBWCs.
One leg is 15 amps, the other 20 amps.

I did not think a asymmetric MBWC was code is it? Is a MWBC one branch circuit, dont both OCPD's have to be the same size?

 

[brycenesbitt]

is there any reason you cannot simply take the 20a circuit down to 15, and put them both on a 15a 2p afci?

The entire apartments only have two circuits.
The 20A runs the Small Appliance Branch Circuits on the kitchen countertop.

Here's the only panel for each unit now. It does appear that's a field installed handle tie:

 

[Master Nater]

But why reduce the circuit when they can use 2 single pole Siemens PON, Easton BR or GE/ABB THQL with handle ties?

good luck doing that with shared neutrals.

 

[curt swartz]

good luck doing that with shared neutrals.

It will work fine. The breaker I listed don't monitor the neutral current.

See page 8 & 9

https://library.e.abb.com/public/80676c8e0c824256befaac27704aeb76/Residential%20Electronic%20Circuit%20Interrupters%201TQC1136E0002%20BR%20REV.B%20OCTOBER%20%202021.pdf?x-sign=2x3eaMHi5x7XG0eSstD0HgxQlnJ510IHax7tpu5creLaapqJsUQjzWssdu2N9oqA

 

[Master Nater]

The entire apartments only have two circuits.
The 20A runs the Small Appliance Branch Circuits on the kitchen countertop.

Here's the only panel for each unit now. It does appear that's a field installed handle tie:
View attachment 2582236

well, the NEC requirement for SMBC is two, 20a circuits. not just one.

there is also, another NEC required circuit for 20a just for the bathroom. and potentially another for laundry and garage, if applicable to the apartment. but if it's small enough to fit everything under a single 15a, it must not be a very large apartment.

 

[pipe_bender]

I still be concerned that the circuit pictured is an existing violation and needs to have a symmetric rating, they should both probably be 20's or both 15's. 225.30 Number of Supplies says in part "a multiwire branch circuit shall be considered a single circuit." 210.18 "Branch circuits recognized by this article shall be rated in accordance with the maximum permitted ampere rating or setting of the overcurrent device. The rating for other than individual branch circuits shall be 15, 20, 30, 40, and 50 amperes."

 

[LarryFine]

I would agree for a 2p breaker, but not two tied 1p breakers.

 

[curt swartz]

I still be concerned that the circuit pictured is an existing violation and needs to have a symmetric rating, they should both probably be 20's or both 15's. 225.30 Number of Supplies says in part "a multiwire branch circuit shall be considered a single circuit." 210.18 "Branch circuits recognized by this article shall be rated in accordance with the maximum permitted ampere rating or setting of the overcurrent device. The rating for other than individual branch circuits shall be 15, 20, 30, 40, and 50 amperes."

There is no requirement that all poles of a multi-wire circuit be the same size. As long a the grounded conductors is sized for the largest circuit you are good.

We used to frequently run multi-wire circuits to detached garages with 1 leg 15A for the lighting and 1 leg 20A for the receptacles.

 

[pipe_bender]

There is no requirement that all poles of a multi-wire circuit be the same size.

The way I read it 225.30 says a MWBC "shall be considered a single circuit."
then 210.18 says "The rating for other than individual branch circuits shall be 15, 20, 30, 40, and 50 amperes."
There is no language in 210.18 that says a combination of sizes is acceptable for a single circuit, like 15/20.

 

[hbiss]

There is no language in 210.18 that says a combination of sizes, like 15/20, its saying the MWBC needs to be 15 or 20.

Key words here are "there is no language in 210.18 that says a combination of sizes". That's how the NEC is written. If it doesn't prohibit something you can do it.

-Hal

 

[pipe_bender]

. If it doesn't prohibit something you can do it.

-Hal

It is prohibiting it, there is no 15/20 in the list, its 15 or 20 not both.

 

[curt swartz]

The way I read it 225.30 says a MWBC "shall be considered a single circuit."
then 210.18 says "The rating for other than individual branch circuits shall be 15, 20, 30, 40, and 50 amperes."
There is no language in 210.18 that says a combination of sizes is acceptable for a single circuit, like 15/20.

Not sure why you are bring up Article 225 since this post is not about the number of supplies feeding a building. It is just saying that if you do have a multi-wire branch circuit feeding a building you can consider it a single circuit.

These is nothing elsewhere in the code that states all overcurrent devices of a multi-wire circuit are required to be the same size.

 

[pipe_bender]

Not sure why you are bring up Article 225 since this post is not about the number of supplies feeding a building. It is just saying that if you do have a multi-wire branch circuit feeding a building you can consider it a single circuit.

These is nothing elsewhere in the code that states all overcurrent devices of a multi-wire circuit are required to be the same size.

I'd tend to agree if the MWBC originated inside. The OP said the breakers were located outside and supplied an apartment, the sole supply.

225.1 Scope. This article covers requirements for outside branch
circuits and feeders run on or between buildings, structures, or
poles on the premises; and electrical equipment and wiring for
the supply of utilization equipment that is located on or attached
to the outside of buildings, structures, or poles.