Multi wire circuit question

Reply

  #1  
Old 07-24-07, 12:47 PM
Member
Thread Starter
Join Date: Mar 2007
Posts: 175
I'm planning a mulitwire circuit dedicated to the disposal/dishwasher. I don't need to hard wire a wall switch for the disposal, as I will be using a countertop pushbutton that plugs into the receptacle. I'll be using a two pole tandem 20A breaker with a common trip. The receptacle under the sink will have the breakout removed on the hot side, with the red wire going to one half and the black wire going to the other half. Both the top and bottom of the receptacle will share the neutral. Is all this OK?
 
Sponsored Links
  #2  
Old 07-24-07, 12:53 PM
Member
Join Date: Sep 2003
Location: Central New York State
Posts: 13,973
Please start a separate thread for a new question.

A tandem breaker is no good. You need a full size (double width) breaker. Tandem implies a mini-breaker which won't work.

I suggest that you wire in a switch, even if you are using something else. Sometime you will want a switch.
 
  #3  
Old 07-24-07, 01:13 PM
Member
Thread Starter
Join Date: Mar 2007
Posts: 175
Sorry about that, thanks for separating this from the old thread.

Oh, that's right, the tandem breaker won't work, because it would only be connected to one of the hots, not both. That's why I check here first! :-)

But if I'm worried about space in the breaker, then I could get a double width breaker that has four breakers on it: either 2-1-1, or 2-2 if I want to share with the 240V A/C, right?
 
  #4  
Old 07-24-07, 01:38 PM
Member
Join Date: Sep 2003
Location: Central New York State
Posts: 13,973
You can certainly buy a quad breaker if you wish.

However, to use a single receptacle for the disposal and the dishwasher you must use a common trip device.

Why not just run two lines of 12-2 or a single line of 12-2-2 and use the tandem breaker?
 
  #5  
Old 07-24-07, 04:06 PM
Member
Thread Starter
Join Date: Mar 2007
Posts: 175
I could run two 12-2 or one 12-2-2. But my panel is starting to get crowded and I figure one less neutral would be helpful. I could just put the disposal and dishwasher on one circuit, but the AHJ likes them on separate circuits.

I'm thinking about your switch idea. The wife is saying she won't do anything but a sinktop pushbutton. On the other hand there's always the chance I may want a switch later, and I'd hate to have to deal with the wiring after the remodel. But I'd hate to have a blank cover plate where a future switch would be. Any thoughts?

BTW, how do the pros feel about DIYers using multiwire circuits? I know that there are additional concerns, especially if you get an open neutral or if you don't use a common trip device. But I figure the risk is minimal if the circuit only goes to one receptacle.
 
  #6  
Old 07-24-07, 08:44 PM
Member
Join Date: Mar 2006
Location: NE Wis / Paris France{ In France for now }
Posts: 4,808
Brian :

I am master electrician and i will fill you in few details with the multiwire branch circuits {MWBC }

it nice for home runs it use little less wires

but only one thing you have to becarefull with the MWBC is that you have two hot on correct sequince like red wire on one hotleg or phase and black on other leg or phase the reason why because this way you can balanced the netural load this way

anytime you get the first junction box for MWBC you must pigtail the netural wire the reason why do this because if you remove the repectale for anyreason you dont break open the netural circuit which it can raise the voltage up to 240 volts and destory any thing is plugged in

the MWBC is very common used in commercal / industrail area dont have much issue with it but have to becarefull with netural loading on both single and three phase system

if you have more question please do post it on the forum thanks


Merci , Marc
 
  #7  
Old 07-25-07, 08:08 AM
Forum Topic Moderator
Join Date: Feb 2005
Location: Near Lansing, Michigan
Posts: 10,342
> But I'd hate to have a blank cover plate where a future switch would be.
> Any thoughts?

Install the switch, but don't hook it up to any wiring; it's a switch that does nothing instead of a blank plate. Some inspectors will gripe about things like that, because they think you're trying to sneak future wiring by them without inspection. Most probably wouldn't mind so long as you explain why you did it. I would definitely make the future provisions for a switch even if you don't intend to use it.

> BTW, how do the pros feel about DIYers using multiwire circuits?

Go for it; you understand the requirements, and you'll use 33% less copper. I don't mind DIYers using multiwire circuits except that there are only a few applications in residential wiring where multiwire circuits are appropriate. Most of the time it's an issue of proper design rather than DIYer skill. A dishwasher/disposal is one of the situations where an MWC is appropriate.
 
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
'