Page 1 of 4 123 ... LastLast
Results 1 to 10 of 40

Thread: mwbc residential

  1. #1
    Join Date
    Jul 2007
    Posts
    16

    mwbc residential

    OK, I never install mwbc in residential applications but I see it frequently. I do mostly service and remodeling work and some of the homes in CA are wired almost exclusively with mwbc. I'm going to start an addition / remodel jub that has been going on for 3 years and I'll be cleaning up from some previous electricians. The last one installed 3 12/3 home runs to the new kitchen with the intent of using 1 for sm. app / disposal another for sm. app / dishwasher and the 3rd for refer / microwave. Since the permit is 3 yrs old, we're dealing with 2005 code. What is the real issue with using these existing home runs? I've never had a problem on small remodels using the original mwbc in kitchens. I see lots of posts where it's said to "stay away from mwbc in residential", Would it be worthwhile to pull these out and re-run. I think one of the reasons he used them is that the neutral bat is getting full in the panel, but I can deal with that issue.

  2. #2
    Join Date
    Dec 2004
    Location
    Fort Collins, CO NEC: 2014
    Posts
    15,429
    No problem. Watch your box fill.

  3. #3
    Join Date
    Jul 2007
    Posts
    16
    Box fill is no problem. Only the refer / micro goes to a sgl gang and it's 20 cu in. The other 2 go into a 2 and 3 gang box.

  4. #4
    Join Date
    Jan 2012
    Location
    Philly Pa burbs
    Posts
    636
    MWBCs shorten the length of the circuits and thereby reduce I^2R heating.
    Proverbs 31;10


  5. #5
    Join Date
    Feb 2009
    Location
    Durango, CO
    Posts
    3,386
    Tear them out, quickly and decisively . Now. Slay this dragon before it can rise up. The MWBC is the worst thing in the electrical world right after Thomas Edison. Not really.

    I don't see a problem either. I use MWBC in resi work.
    If Billy Idol or John Denver is on your Ipod go and re-evaluate your life.

  6. #6
    Join Date
    Jan 2012
    Location
    Philly Pa burbs
    Posts
    636
    I have heard that MWBCs are the work of the devil

    Name:  185px-Flandersdevil.gif
Views: 893
Size:  7.2 KB
    Proverbs 31;10


  7. #7
    Join Date
    Feb 2009
    Location
    Durango, CO
    Posts
    3,386
    Oh, they are. And those that practice the use of them are his hands.
    If Billy Idol or John Denver is on your Ipod go and re-evaluate your life.

  8. #8
    Join Date
    May 2005
    Location
    Tacoma, WA
    Posts
    165
    Instead of 'mwbc', please refer to it as the 'circuit that shall not be named'. It's better luck.

    Actually, the only real issue is that you can't use GFI or AFCI breakers. And if the (proper) two-pole breaker is turned off, BOTH circuits get turned off.

  9. #9
    Join Date
    Jul 2007
    Posts
    16
    If I'm working on a 3 year old permit, I should be working on 2005 code (CA just started using 2008 in 2011) and I shouldn't need to use handle ties or 2-pole breakers. None of the circuits will be arc fault and the sm app will use GFCI receptacles.

  10. #10
    Join Date
    Feb 2007
    Location
    USA
    Posts
    3,796
    Okay you might not need to use 2 pole breakers however is good practice in a residential situation as it breaks both circuits.
    Also you need to pigtail your nuetral as you cannot be able to remove a device that in turn breaks the nuetral connection. No 3 wires downstream of a GFCI either. Follow this and the DEvil will stay away

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •