20A two pole breakers

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olly

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Location
Berthoud, Colorado
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Master Electrician
If I do a multiwire wire branch circuit 12-3 on a double pole gfci / afci breaker... Obviously one neutral, two separate 120v circuits, this breaker will operate correctly? Rookie question... I don't do a lot of residential work.
 
olly said:
If I do a multiwire wire branch circuit 12-3 on a double pole gfci / afci breaker... Obviously one neutral, two separate 120v circuits, this breaker will operate correctly? Rookie question... I don't do a lot of residential work.
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It will.
 
Welcome. To add, the circuit neutral must also land on the breaker, and its white wire connected to the panel neutral bus.
 
I would run 2 separate circuits. It is not worth the hassle to run a multiwire branch circuit and use a dp setup
 
I agree with Dennis; unless there is a compelling reason to do so, don't use MWBCs. It's no longer the cost saver it used to be.
 
olly said:
If I do a multiwire wire branch circuit 12-3 on a double pole gfci / afci breaker... Obviously one neutral, two separate 120v circuits, this breaker will operate correctly? Rookie question... I don't do a lot of residential work.
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Olly, with due deference to the answers you've been given by Larry and Dennis, the answer is really answers.
  1. Is the panel either a GE or Eaton BR? All AFCIs are not the same.
  2. Is the 12/3 branch circuit existing? Existing MWBC can be hard to change to two two-wire branch circuits.
Do you actually have to have the Ground Fault detection at the breaker?

A little more information about the hardware / branch circuits that you are considering will go a long way to improving the answers here.
 
al hildenbrand said:
Olly, with due deference to the answers you've been given by Larry and Dennis, the answer is really answers.
  1. Is the panel either a GE or Eaton BR? All AFCIs are not the same.
  2. Is the 12/3 branch circuit existing? Existing MWBC can be hard to change to two two-wire branch circuits.
Do you actually have to have the Ground Fault detection at the breaker?

A little more information about the hardware / branch circuits that you are considering will go a long way to improving the answers here.
Click to expand...

Its a new install and no it doesn't have to be AFCI. Just a regular 2 pole breaker, I have realized that through a previous question asked. So is a MWBC still a cost saver if you don't have to buy AFCI or CFGI?
 
olly said:
So is a MWBC still a cost saver if you don't have to buy AFCI or CFGI?
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The best way to know that is to price it both ways. Remember to consider labor involved with joints, especially where the MWBC becomes two 2-wire circuits.
 
olly said:
Its a new install and no it doesn't have to be AFCI. Just a regular 2 pole breaker, I have realized that through a previous question asked. So is a MWBC still a cost saver if you don't have to buy AFCI or CFGI?
Click to expand...

If the only measure is the dollars and cents for the labor of installation, and the multiwire branch circuit (MWBC) does not require either (or both) arc-fault detection or ground-fault detection, then, yes.

In new construction residential, the non-AF, non-GF branch circuit or outlets are getting to be rare, so, in my opinion, the "yes" answer is hard to put into practice.

I've always liked MWBCs, in part, because they help with voltage drop under normal operating conditions with loads running on both sides of the MWBC.

Besides the labor / material cost of installation, I also consider the occupant experience using the wiring, as well as the cost to the owner and the electrician for call-backs and / or troubleshooting over the life of the installation.

To me, the down side of ANY two-pole AF or GF breaker is that a greater area is shut off upon trip from a fault only on one side of the MWBC. The work of troubleshooting such a fault is more time consuming to isolate and identify. From the occupant's experience, the tripping behavior of ANY two-pole AF or GF breaker is much more likely to be confusing, leading to the expense of having to call in a good troubleshooter.
 
olly said:
Its a new install and no it doesn't have to be AFCI. Just a regular 2 pole breaker, I have realized that through a previous question asked. So is a MWBC still a cost saver if you don't have to buy AFCI or CFGI?
Click to expand...

If AFCI/GFCI is not needed, you save amount of copper needed if you run 1 neutral instead of 2, and 1 EGC instead of 2. If it is a short run, that savings may be somewhat negligible if it is a long run it can be significant.
 
kwired said:
If AFCI/GFCI is not needed, you save amount of copper needed if you run 1 neutral instead of 2, and 1 EGC instead of 2. If it is a short run, that savings may be somewhat negligible if it is a long run it can be significant.
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Strangely enough, look at the pricing of 2 lengths of 12-2 nm versus 1 length of 12-3 nm. The 12-3 (with 4 total conductors) costs almost as much as 2 pieces of 12-2 (with 6 total conductors). So even though you are saving the planet in terms of actual material used, you don't really save your wallet.

Though pricing can be funny. Last week I bought 12-3 stranded MC for less than 12-2 stranded....

-Jon
 
winnie said:
Strangely enough, look at the pricing of 2 lengths of 12-2 nm versus 1 length of 12-3 nm. The 12-3 (with 4 total conductors) costs almost as much as 2 pieces of 12-2 (with 6 total conductors). So even though you are saving the planet in terms of actual material used, you don't really save your wallet.

Though pricing can be funny. Last week I bought 12-3 stranded MC for less than 12-2 stranded....

-Jon
Click to expand...

There are labor differences, short run they may be minimal, long run may be significant enough. Really long run where you end up increasing conductor size because of VD, may definitely make a difference, might not be too common to run into this for a typical dwelling though.
 
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