12/3 Romex to 2 20A Circuits

Reply

  #1  
Old 08-03-19, 08:57 AM
Member
Thread Starter
Join Date: Nov 2005
Location: usa
Posts: 83
Received 0 Votes on 0 Posts
12/3 Romex to 2 20A Circuits

I'd like to confirm that I need to use 2 separate "normal" size 20A circuit breakers and not a single "tandem" circuit breaker when creating 2 separate circuits with one 12/3 wire. I've attached a picture of the available space at the box.

Tks....Mike

Name:  bk1.jpg
Views: 106
Size:  87.2 KB
 

Last edited by PJmax; 08-03-19 at 09:17 AM. Reason: resized picture
Sponsored Links
  #2  
Old 08-03-19, 09:18 AM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 52,589
Received 337 Votes on 315 Posts
You need to use a 2P20A breaker.
That would be two twenty amp breakers in one case typically used for 240v circuits.
This is done so that both circuits that share a common neutral are shut off together.

Square D 2P20 breaker
 
  #3  
Old 08-03-19, 09:41 AM
Member
Thread Starter
Join Date: Nov 2005
Location: usa
Posts: 83
Received 0 Votes on 0 Posts
Thank you Pete. Only for sake of knowing better, I've attached another picture showing 2 different ones - I'm assuming you meant for me to use the top breaker? Not to question your suggestion, but what is the difference between that and the bottom breaker (price is not a factor)? Tks!
 
Attached Images  
  #4  
Old 08-03-19, 09:44 AM
Tolyn Ironhand's Avatar
Group Moderator
Join Date: Nov 2007
Location: Twin Cities, MN
Posts: 12,933
Received 54 Votes on 47 Posts
The top breaker is a Square D QO breaker. It will not fit your panel. The bottom picture is the correct breaker for your panel. (Square D Homeline)
 
  #5  
Old 08-03-19, 09:48 AM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 52,589
Received 337 Votes on 315 Posts
There are two different panels...... Homeline and QO. The breakers are not interchangeable.
Look on your existing breakers for the type.

Thanks T. I should have looked at the original picture closer.
 
  #6  
Old 08-03-19, 10:25 AM
Member
Thread Starter
Join Date: Nov 2005
Location: usa
Posts: 83
Received 0 Votes on 0 Posts
okay....sounds good. Tks! And the reason for using a double pole and not 2 single 20A is because it's sharing a common white wire? So when I cut the circuit for one, they both go off.
 
  #7  
Old 08-03-19, 11:08 AM
Member
Join Date: Sep 2002
Location: welland ontario
Posts: 6,670
Received 74 Votes on 68 Posts
Yes. Code requires both circuits to go off together on a shared neutral circuit.
You also need to be sure you install the breaker in a slot where you get 240 volts between the hots. The empty slot in your picture is fine.
 
  #8  
Old 08-03-19, 03:18 PM
Member
Join Date: Feb 2016
Location: United States, Virginia
Posts: 1,149
Received 21 Votes on 17 Posts
You can also use two single pole breakers with the approved handle tie. The advantage of two singles tied together is if one circuit trips due to a fault the second circuit will stay live. Using a two pole common trip breaker will trip on both legs regardless of which leg had the fault. The simultaneous disconnect of both circuits is required for servicing, not for faults.
 
  #9  
Old 08-04-19, 05:30 AM
Member
Join Date: Mar 2014
Posts: 440
Received 5 Votes on 5 Posts
The advantage of two singles tied together is if one circuit trips due to a fault the second circuit will stay live.




If two single pole breakers are used instead of one two pole breaker and the two single pole breakers have a tie-bar installed as per code requirements then if one trips the other will trip with it - thus the requirement for the tie-bar. One circuit should not stay live if the other one trips on a MWBC. If one does stay live then the tie-bar is not installed correctly or the wrong one is being used. Always best to use one two pole breaker.
 
  #10  
Old 08-04-19, 06:48 AM
Member
Join Date: Feb 2016
Location: United States, Virginia
Posts: 1,149
Received 21 Votes on 17 Posts
All I can say is you are wrong. Two single pole breakers with a handle tie does not provide common trip. Test it for yourself. The breaker trips internally and the handle relaxes to the center point and does not have the force to trip the second breaker. Handle ties are not designed to provide common trip. Common trip is only required when the MWBC is serving line-to-line loads. This is why there are common trip 2P breakers.

Edit: I should say that doesn't mean there are not single breaks out there where the handle tie will trip both single breakers on a fault. The only ones I can attest that I have used and don't are Square-D and Eaton.

See: https://www.schneider-electric.us/en/faqs/FA112337/
 
CasualJoe voted this post useful.

Last edited by pattenp; 08-04-19 at 08:24 AM. Reason: Added link
  #11  
Old 08-04-19, 02:55 PM
Tolyn Ironhand's Avatar
Group Moderator
Join Date: Nov 2007
Location: Twin Cities, MN
Posts: 12,933
Received 54 Votes on 47 Posts
One circuit should not stay live if the other one trips on a MWBC.
The purpose of the handle tie is for a common disconnect on a MWBC as required by code. A common trip is not required.
 
CasualJoe voted this post useful.
  #12  
Old 08-04-19, 03:30 PM
pcboss's Avatar
Forum Topic Moderator
Join Date: Jul 2002
Location: Maryland
Posts: 14,909
Received 24 Votes on 20 Posts
Depending on the code cycle enforced you may need afci protection for both circuits. Those breakers shown do not provide that protection. Many panels do not have afci protection in a two pole breaker.
 
Reply

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


Thread Tools
Search this Thread
Display Modes
 
Ask a Question
Question Title:
Description:
Your question will be posted in: