Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Electrical

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Search this Thread Display Modes
Old 09-29-2011, 09:51 AM   #1
Newbie
 
Join Date: Jan 2007
Location: NJ
Posts: 24
Share |
Default

MWBC's - 2006, Do I need to make any changes?


Hi guys,
I am in the process of hooking up a Manual Transfer switch for use with a portable generator. While doing my homework and identifying which circuits do what in my panel, I learned something besides do not always go by what the breaker is labeled! I see I have 4 MWBC's. It took a little bit to identify the matching breaker for each as none of them are handle-tied together. My home was built new in 2006, so I am not sure if it was required then, but from I have read online these should really be tied together. The circuit breakers in question are all on the left side and 3 of the 4 pairs are not next to each other (stacked above each other).

Since I am in the box anyway should I move a couple of them so they are then stacked above each other and then handle tie each of them together? For example - if you go down the left side of my box: 1,3,5,7,9,11,13,15,17,19,21

Of which:
5 & 13 are a MWBC
7 & 11 are a MWBC
9 & 15 are a MWBC

and 19 and 21 are as well, but they are already stacked above each other - just not tied.

So if I were to switch the wires from #5 with #15 and then #7 with #9, that would put me as 5 & 7 stacked and 9 & 11 stacked and 13 & 15 stacked. Then I could handle tie them together (assuming they sell the ties at the HD or L).

Is this something I should do or is it not necessary - I appreciate any feedback.

Thanks!

tbone2004 is offline   Reply With Quote
Old 09-29-2011, 09:58 AM   #2
I=E/R
 
a7ecorsair's Avatar
 
Join Date: May 2010
Location: Minnesota
Posts: 2,052
Default

MWBC's - 2006, Do I need to make any changes?


Is your wiring done with romex cable so each cable that supports a MWBC has a red and black wire?

a7ecorsair is offline   Reply With Quote
Old 09-29-2011, 10:09 AM   #3
Newbie
 
Join Date: Jan 2007
Location: NJ
Posts: 24
Default

MWBC's - 2006, Do I need to make any changes?


Quote:
Originally Posted by a7ecorsair View Post
Is your wiring done with romex cable so each cable that supports a MWBC has a red and black wire?
Yes, the four feeds in question are 4-wire: red, black, white, grd
tbone2004 is offline   Reply With Quote
Old 09-29-2011, 10:21 AM   #4
I=E/R
 
a7ecorsair's Avatar
 
Join Date: May 2010
Location: Minnesota
Posts: 2,052
Default

MWBC's - 2006, Do I need to make any changes?


Quote:
Originally Posted by tbone2004 View Post
Yes, the four feeds in question are 4-wire: red, black, white, grd
Not to challenge your work but is seems strange that the MWBC breakers aren't next to each other already. Moving the wires so the red and black from each romex cable connects to adjacent breakers makes sense to me. Just double check your work...
a7ecorsair is offline   Reply With Quote
Old 09-29-2011, 10:24 AM   #5
Just call me Andrew
 
Join Date: Mar 2009
Location: Albany, NY
Posts: 2,252
Default

MWBC's - 2006, Do I need to make any changes?


MWBC breakers must be 2-pole or adjacent single-pole with handle ties.

I have a friend who had a MWBC on breakers nowhere near each other in the panel....so it can happen.
__________________
Andrew

secutanudu is offline   Reply With Quote
Old 09-29-2011, 10:28 AM   #6
Newbie
 
Join Date: Jan 2007
Location: NJ
Posts: 24
Default

MWBC's - 2006, Do I need to make any changes?


Quote:
Originally Posted by a7ecorsair View Post
Not to challenge your work but is seems strange that the MWBC breakers aren't next to each other already. Moving the wires so the red and black from each romex cable connects to adjacent breakers makes sense to me. Just double check your work...
I agree about the strangeness - so part of me is saying leave well enough alone and I could make a note on the box that says hey, if you are working on circuit#5, you should switch off BOTH #5 AND #13 to be safe.

The other part of me is saying, since I am going to be in there anyway maybe I should tidy up a little, cause maybe an inspector missed it in 2006.

Does it matter between the two breakers of a MWBC which gets the red and which gets the black? Probably a dumb question - but was always taught no question is dumb.

thanks
tbone2004 is offline   Reply With Quote
Old 09-29-2011, 10:33 AM   #7
Just call me Andrew
 
Join Date: Mar 2009
Location: Albany, NY
Posts: 2,252
Default

MWBC's - 2006, Do I need to make any changes?


Quote:
Originally Posted by tbone2004 View Post
part of me is saying leave well enough alone and I could make a note on the box that says hey, if you are working on circuit#5, you should switch off BOTH #5 AND #13 to be safe.

This is not good enough in my (and the NEC's) opinion. The breakers must turn on and off simultaneously (Either 2-pole or handle ties).


The colors of the wires don't matter.
__________________
Andrew

secutanudu is offline   Reply With Quote
Old 09-29-2011, 10:43 AM   #8
Newbie
 
Join Date: Jan 2007
Location: NJ
Posts: 24
Default

MWBC's - 2006, Do I need to make any changes?


Quote:
Originally Posted by secutanudu View Post
This is not good enough in my (and the NEC's) opinion. The breakers must turn on and off simultaneously (Either 2-pole or handle ties).


The colors of the wires don't matter.
I am with you. Was it maybe not code in 2006?
Either way - with the move of a couple wires I can then handle tie the breakers - and I think that is safer for everyone..me and the next owner of the home years from now.

thank you for the immediate replies.
tbone2004 is offline   Reply With Quote
Old 09-29-2011, 10:55 AM   #9
Licensed electrician
 
Join Date: Sep 2007
Location: Maryland
Posts: 7,410
Default

MWBC's - 2006, Do I need to make any changes?


If both of the hots are on the same leg of the panel you risk overloading the neutral as the current will be additive instead of the difference between the two legs. The neutral could overheat and cause a fire and could potentially carry 2x the current it should. The breaker would not trip to prevent a fire.

Common trips were only required if the 2 hots landed on the same device yoke. Now the code has changed to require both hots to turn off together regardless.
__________________
Answers based on the National Electrical Code. Local amendments may apply. Check with your local building officials.
Jim Port is offline   Reply With Quote
The Following User Says Thank You to Jim Port For This Useful Post:
secutanudu (09-29-2011)
Old 09-29-2011, 11:25 AM   #10
Newbie
 
Join Date: Jan 2007
Location: NJ
Posts: 24
Default

MWBC's - 2006, Do I need to make any changes?


Quote:
Originally Posted by Jim Port View Post
If both of the hots are on the same leg of the panel you risk overloading the neutral as the current will be additive instead of the difference between the two legs. The neutral could overheat and cause a fire and could potentially carry 2x the current it should. The breaker would not trip to prevent a fire.

Common trips were only required if the 2 hots landed on the same device yoke. Now the code has changed to require both hots to turn off together regardless.
Hey Jim - I have read a little about that and have wondered how would I know which leg it is on? How can I tell. I was concerned initially as all mine run down the left side - but someone said somehwere in my reading that may be fine because some panels are ababababab.... if that makes snese. Is there a way for me to be sure I am on diff legs?
tbone2004 is offline   Reply With Quote
Old 09-29-2011, 11:27 AM   #11
Just call me Andrew
 
Join Date: Mar 2009
Location: Albany, NY
Posts: 2,252
Default

MWBC's - 2006, Do I need to make any changes?


Use a multimeter and check voltage between the screws on the two breakers in question. It'll be 240 if you are on different legs.
__________________
Andrew

secutanudu is offline   Reply With Quote
The Following User Says Thank You to secutanudu For This Useful Post:
tbone2004 (09-29-2011)
Old 09-29-2011, 11:41 AM   #12
Member
 
joed's Avatar
 
Join Date: Mar 2005
Location: Welland, Ontario
Posts: 7,393
Default

MWBC's - 2006, Do I need to make any changes?


If your panel is full of half size, mini, tandem breakers, what ever name you call them, you need to be very careful. You can easily get two brekers side by side that are on the same leg.

Use a volt meter to measure the voltage between the two breakers. It must be 240 volts. You can do this even before you move any wires around.
__________________
Do not PM with questions that can be asked in a forum. I will not respond.
joed is offline   Reply With Quote
Old 09-29-2011, 04:56 PM   #13
Newbie
 
Join Date: Jan 2007
Location: NJ
Posts: 24
Default

MWBC's - 2006, Do I need to make any changes?


Quote:
Originally Posted by secutanudu View Post
Use a multimeter and check voltage between the screws on the two breakers in question. It'll be 240 if you are on different legs.
OK, I went home and did some testing/measuring with my meter as recommended.

1) Voltage across existing MWBC 9 and 15 is @248
2) Voltage across existing MWBC 19 and 21 is @248

So for these two - although not being adjacent to one another and therefore not tied, they are at least on diff legs - so no issue other than not tied together. I also saw that voltage across ckt 9 and 11 is 248, so I could make my move I described earlier to get them so they can be adjacent and therefore tied. 19 and 21 are already adjacent to one another - just not tied (yet)

3) Voltage across existing MWBC 5 and 13 is 0
4) Voltage across existing MWBC 7 and 11 is 0

So according to what I have read here and other boards, this is bad - correct?

If it makes any difference -

Bkr#5 is my 2nd floor furnace and bkr#13 is the foyer light, 2nd floor hallway high-hats, some 2nd floor bedroom high-hats

Bkr#11 is my first floor furnace and bkr#7 is the light going down to the basement and a GCFI outlet in the basement.

(Not sure if this makes any difference as far as getting a 0 reading for each of these two MWBC's but just wanted to provide as many facts as I can.)

I also saw that across breaker #13 and breaker #15 I get @248 and across bkr #5 & bkr #7 I get @248 --- so I should also be able to make my moves I mentioned earlier to end up with my MWBC's being located as:

bkrs 5&7 - tied
bkrs 9&11 - tied
bkrs 13&15 - tied
bkrs 19&21 - tied

Does this sound valid?
Is there a reason that any of you guys, (who know a lot more than me) can think of why I would get 0 voltage across the two MWBCs I indicated other then they are simply wired wrong? (yes, I triple checked that the wires are going to the indicated breakers)

I also did a test where I shut off bkr #7 but bkr #11 was still on - no voltage at the outlet connected to #7. Not sure if I was expecting there to be voltage - or is it just there lies the possibility to be voltage??

Please let me know what you think. Not sure if I want to go back to the electrician - it has been 5 years now like this - or just clean it up myself.

Thanks all for any replies.
tbone2004 is offline   Reply With Quote
Old 09-29-2011, 05:06 PM   #14
Electrical Contractor
 
jbfan's Avatar
 
Join Date: Jun 2004
Location: Newnan GA
Posts: 5,696
Default

MWBC's - 2006, Do I need to make any changes?


As you found out, 0 volts across 2 breakers indicated they are on the same leg.

As long as you are sure they are indeed MWBC, then I would make the changes you have talked about.

You don't list the make of the panel, but HD and Lowes carry handle ties for most.
__________________
Yes I am a Pirate, 200 years too late. "Jimmy Buffett"
jbfan is offline   Reply With Quote
Old 09-29-2011, 05:54 PM   #15
Newbie
 
Join Date: Jan 2007
Location: NJ
Posts: 24
Default

MWBC's - 2006, Do I need to make any changes?


Quote:
Originally Posted by jbfan View Post
As you found out, 0 volts across 2 breakers indicated they are on the same leg.

As long as you are sure they are indeed MWBC, then I would make the changes you have talked about.

You don't list the make of the panel, but HD and Lowes carry handle ties for most.
Oops - sorry, I even wrote it down before I came upstairs...

It is a GE Powermark Gold Load Center
Type 1 Indoor Enclosure
Front Cat No. TM40BCD

Use with GE Load Center Enclosure TM4020 CCU Mod 6

(not sure if that helps - I guess "GE" would probably be the quicker answer )

tbone2004 is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Commenting on Behr Paints athanman Painting 657 02-12-2012 04:21 PM
MWBC's for Dedicated Circuits? mysterylectric Electrical 37 07-09-2011 10:36 PM
IRC 2006 Effective Date? EWen Building & Construction 0 01-23-2011 02:57 PM
FREE plans/instructions for easy to make Magic Box! DangerMouse General DIY Discussions 5 07-23-2009 04:14 PM
Want to make cuts in cabinet walls to put in shelfs humberguy Carpentry 3 07-09-2009 09:07 PM




Top of Page | View New Posts

Copyright © 2003-2014 Escalate Media. All Rights Reserved.