Installation For 120v Generator Feed -- How To Split 3-Wire Romex Fed "Dual Circuits" - Electrical - DIY Chatroom Home Improvement Forum
Advertisement


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


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

Like Tree10Likes
Reply
 
Thread Tools Display Modes
Old 01-03-2017, 06:15 PM   #1
Newbie
 
Join Date: May 2010
Posts: 17
Rewards Points: 26
Default

Installation For 120v Generator Feed -- How To Split 3-Wire Romex Fed "Dual Circuits"


Hello.

I would like to install a 120 volt load center (I would use one hot lead to power both legs) and manual transfer switch (a 3 pole, double throw, non-fused device) to accommodate the use of a Honda 120v portable generator (an EU 2000i).

I am intending to power an oil burner and related hot water circulation pumps, one refrigerator and one deep freezer plus a few lights. I am hoping that the 2000 peak watts supplied by the Honda will be sufficient but will obviously stagger turning on the motor loads.

It looks like I'll have at total of 5 individual 120v circuits to transfer to the new 120v load center. That load center would be fed off only one of the hot legs of the main panel using a single 30 amp breaker (via the manual transfer switch).

I've got two questions. I see upon opening the main panel that the some of the 120v circuits were wired with 3-wire (red hot, black hot, white neutral and ground) romex in which the two hot leads (red and black) feed two different 120v circuits. I understand that this is legit assuming that the two hot leads are on different legs of the main panel (let's call 'em Hot 1 and Hot 2) so that the maximum current seen by the neutral would only be the difference between the red and black loads and not the sum (e.g. if the red was feeding in 20 amps and the black only 5, the white neutral would "see" only 15 amps). But I think this existing arrangement makes my plan difficult to execute.

For example, I see that there is one circuit I'd like to transfer to the new load center which is one-half one of these 3-wire arrangements. First issue is that I can only transfer one of these two circuits (otherwise I'd be doubling up on the white neutral). Assuming I do transfer one of these circuits, how to I physically separate the two circuits? Do I need to use a junction box where the red and black leads split off but where the white and ground are spliced such that two white wires and two ground wires leave the junction box with one going to the main panel and the other to the new load center? And wouldn't it be prudent to label each of the two breakers or wires connected to each of the respective breakers to ensure that it is clear that the two breakers need to be connected to separate hot legs?

Sorry if my terminology usage is not quite right, but hopefully I've been clear in describing the issue.

Advertisement

diycc2 is offline   Reply With Quote
Old 01-03-2017, 10:25 PM   #2
Newbie
 
Join Date: May 2010
Posts: 17
Rewards Points: 26
Default

Re: Installation For 120v Generator Feed -- How To Split 3-Wire Romex Fed "Dual Circu


I may have used wrong terminology above. What I would be trying to do is to separate the two breakers for two circuits which are currently wired using 3-wire romex with a shared neutral (and shared ground). I'm would be moving one breaker to a new generator fed load center and keeping the other breaker isn the main panel. I realize that two breakers would need to continue to draw off of different legs so as to avoid overloading the shared neutral (which would continue to be shared downstream of the panels).

Advertisement

diycc2 is offline   Reply With Quote
Old 01-04-2017, 12:14 AM   #3
Newbie
 
Join Date: May 2010
Posts: 17
Rewards Points: 26
Default

Re: Installation For 120v Generator Feed -- How To Split 3-Wire Romex Fed "Dual Circu


Thought about it some more. I don't think it can be done. Even if two breakers on shared neutral circuits are put into two different load centers (one stays in main panel and other goes into switched small load center such that they are fed by different hot legs), while no problem would occur if everything is on the mains, if small load center is switched to generator and mains power is restored the shared neutral will become overloaded (inasmuch as generator "leg" and utility leg are not going to be 180 degrees out of phase). Unless anyone sees solution other than re-doing home runs from shared neutral circuits, I'm gonna call the SOB "electrician" who initially wired this house and tell him off. Shared neutrals are stupid and dangerous and save virtually no cost.

Anyone see a reasonable solution to this problem?
diycc2 is offline   Reply With Quote
Old 01-04-2017, 12:23 AM   #4
Member
 
joed's Avatar
 
Join Date: Mar 2005
Location: Welland, Ontario
Posts: 12,362
Rewards Points: 11,516
Blog Entries: 11
Default

Re: Installation For 120v Generator Feed -- How To Split 3-Wire Romex Fed "Dual Circu


Transfer switch should open the neutral.
joed is offline   Reply With Quote
Old 01-04-2017, 12:42 AM   #5
Member
 
Join Date: May 2015
Location: Canada
Posts: 3,317
Rewards Points: 42
Default

Re: Installation For 120v Generator Feed -- How To Split 3-Wire Romex Fed "Dual Circu


Get the bigger eu7000 so that you have 240v then you can still use your shared neutral run. I don't like them either....

Alternative: use a transformer to get your center tapped 240v instead. Probably about the same price in the end, I'd go with the bigger geny.

I *think* that I remember seeing some inverter type genys that are in the 3000w range with 240v. They weren't Honda, and I don't remember who made it, sorry.

As for all the code side of it, I won't be of much help.

Cheers!
supers05 is offline   Reply With Quote
Old 01-04-2017, 12:44 AM   #6
Newbie
 
Join Date: May 2010
Posts: 17
Rewards Points: 26
Default

Re: Installation For 120v Generator Feed -- How To Split 3-Wire Romex Fed "Dual Circu


Quote:
Originally Posted by joed View Post
Transfer switch should open the neutral.

Transfer switch will switch the neutral between generator and utility on one circuit only. The other circuit's neutral will remain connected to utility. This creates fatal problem when small load center is on generator and utility power comes on. At that point neutral is "returning" current from both utility and generator causing an overload on the shared portion of neutral. Helps to sketch it out perhaps.
diycc2 is offline   Reply With Quote
Old 01-04-2017, 12:52 AM   #7
Newbie
 
Join Date: May 2010
Posts: 17
Rewards Points: 26
Default

Re: Installation For 120v Generator Feed -- How To Split 3-Wire Romex Fed "Dual Circu


Quote:
Originally Posted by supers05 View Post
Get the bigger eu7000 so that you have 240v then you can still use your shared neutral run. I don't like them either....

Alternative: use a transformer to get your center tapped 240v instead. Probably about the same price in the end, I'd go with the bigger geny.

I *think* that I remember seeing some inverter type genys that are in the 3000w range with 240v. They weren't Honda, and I don't remember who made it, sorry.

As for all the code side of it, I won't be of much help.

Cheers!
Ha! I should solve the problem by avoiding the problem. Well, just so happens that I had a full house generator previously wired. That had to be abandoned after using it a few years for various reasons. I now intend to put in a natural gas-fueled fully standby generator but this will not be possible for a few years as the idiots at the gas utility company have a moratorium on new hook ups due to poor welds on their new natural gas pipeline. So I'm going to use a small portable Honda to run oil heat and a few other circuits. I'll get around this somehow even if I have to run a few new circuits myself. I'm going to kill ( ) that POS "professional" electrician though.
diycc2 is offline   Reply With Quote
Old 01-04-2017, 12:55 AM   #8
Member
 
Join Date: May 2015
Location: Canada
Posts: 3,317
Rewards Points: 42
Default

Re: Installation For 120v Generator Feed -- How To Split 3-Wire Romex Fed "Dual Circu


Quote:
Originally Posted by diycc2 View Post
Ha! I should solve the problem by avoiding the problem. Well, just so happens that I had a full house generator previously wired. That had to be abandoned after using it a few years for various reasons. I now intend to put in a natural gas-fueled fully standby generator but this will not be possible for a few years as the idiots at the gas utility company have a moratorium on new hook ups due to poor welds on their new natural gas pipeline. So I'm going to use a small portable Honda to run oil heat and a few other circuits. I'll get around this somehow even if I have to run a few new circuits myself. I'm going to kill ( ) that POS "professional" electrician though.
Do you already have gas to your house? If you did, I just wouldn't tell them. Lol

Many of the gas portables can be converted to NG with demand regulators. The eu7000 seems to be left out though... (fuel injection, no carb to make it easy for the retrofit. )

Cheers!

Last edited by supers05; 01-04-2017 at 12:58 AM.
supers05 is offline   Reply With Quote
Old 01-04-2017, 01:09 AM   #9
Member
 
Join Date: Jul 2016
Posts: 139
Rewards Points: 278
Default

Re: Installation For 120v Generator Feed -- How To Split 3-Wire Romex Fed "Dual Circu


I thought your description was fine. The technical term is a multiwire branch circuit (MWBC) and your understanding of it is correct.

That unfortunately also means you understand why your plans won't work with your current circuit. Besides the technical problem of the 120V generator, you also have code issues you cannot resolve. The MWBC circuit must be fed with a common trip circuit breaker or one with direct handle ties. Thus you cannot separate the hot feeds between the two panels.

Quote:
Shared neutrals are stupid and dangerous and save virtually no cost.
In a residential setting you are absolutely right. It's mainly laziness that gets them installed inside a home. The only good use of a MWBC in a residence is to feed a detached garage or outbuilding without the cost and hassle of setting up a full panel.
Fishbulb28 is online now   Reply With Quote
Old 01-04-2017, 05:29 AM   #10
A "Handy Husband"
 
rjniles's Avatar
 
Join Date: Feb 2007
Location: South Carolina Low Country
Posts: 7,221
Rewards Points: 4,032
Default

Re: Installation For 120v Generator Feed -- How To Split 3-Wire Romex Fed "Dual Circu


Your rants about the electrician are misplaced. MWBC are common practice, if you didn't want the house wired that way you should have told him so.

Sent from my RCT6203W46 using Tapatalk
__________________
Location:
Coastal South Carolina
rjniles is online now   Reply With Quote
The Following User Says Thank You to rjniles For This Useful Post:
Jim Port (01-05-2017)
Old 01-04-2017, 08:44 AM   #11
Member
 
Join Date: May 2015
Location: Canada
Posts: 3,317
Rewards Points: 42
Default

Re: Installation For 120v Generator Feed -- How To Split 3-Wire Romex Fed "Dual Circu


Quote:
Originally Posted by rjniles View Post
Your rants about the electrician are misplaced. MWBC are common practice, if you didn't want the house wired that way you should have told him so.

Sent from my RCT6203W46 using Tapatalk
While your assertions may(or may not) be correct about the OPs case, I actually found one in my house the other day. While doing some work in the panel, I saw a MWBC, which at the time I assumed was a 240v line, so I shut it off. (been removing most of my 240v loads as electricity is too expensive here, so at this time of year I have no 240v loads.) Of course in this old house, nothing is labeled, and it ended up being an outlet instead. Now I just have to go find a breaker tie for it......

The things i find out about this old house...

Cheers!

Last edited by supers05; 01-04-2017 at 08:51 AM.
supers05 is offline   Reply With Quote
Old 01-04-2017, 01:01 PM   #12
Electrical Contractor
 
jbfan's Avatar
 
Join Date: Jun 2004
Location: Newnan GA
Posts: 6,772
Rewards Points: 138
Default

Re: Installation For 120v Generator Feed -- How To Split 3-Wire Romex Fed "Dual Circu


For those bashing MWBC's, remember that your house is fed by one.
Unless you have a 120v service.
beenthere, Oso954 and clw1963 like this.
__________________
"The problem isn't that Hillary Clinton lies. We all know she lies. The problem is that her supporters don't seem to care"
jbfan is offline   Reply With Quote
The Following 2 Users Say Thank You to jbfan For This Useful Post:
Jim Port (01-05-2017), rjniles (01-04-2017)
Old 01-04-2017, 07:03 PM   #13
Member
 
Join Date: May 2015
Location: Canada
Posts: 3,317
Rewards Points: 42
Default

Re: Installation For 120v Generator Feed -- How To Split 3-Wire Romex Fed "Dual Circu


Quote:
Originally Posted by jbfan View Post
For those bashing MWBC's, remember that your house is fed by one.
Unless you have a 120v service.
Legacy persistence.... I'd prefer 3 phase personally. Anyways, my problem isn't the wiring, my problem is my lack of labeling. Not an electricians problem

Cheers!
jbfan likes this.

Last edited by supers05; 01-04-2017 at 07:05 PM.
supers05 is offline   Reply With Quote
Old 01-04-2017, 08:44 PM   #14
Newbie
 
Join Date: May 2010
Posts: 17
Rewards Points: 26
Default

Re: Installation For 120v Generator Feed -- How To Split 3-Wire Romex Fed "Dual Circu


Quote:
Originally Posted by rjniles View Post
Your rants about the electrician are misplaced. MWBC are common practice, if you didn't want the house wired that way you should have told him so.

Sent from my RCT6203W46 using Tapatalk
Really? I think not.

First of all, the electrician was told that we would, in the future, be installing a generator. Of course if this "electrician" had an IQ north of 100, he would not have inextricable tied a number of circuits together knowing that there was at least a possibility of the installation of a mini-load center with segregated circuits. Secondly, it is both stupid and dangerous to use a shared neutral -- do you know why? Thirdly, this lazy dimwit used standard breakers just to make sure he put some innocent party at risk (do you know why that's a risk -- hint it relates to turning off one breaker while the other breaker feeds the shared neutral?).

Finally, this brain surgeon made other lazy-azz blunders like attaching the recirculating pump controller box (electronics) to the sheet metal covering of the hot water boiler -- this would not only fry the electronics over time, it also prevented removal of the cover in order to clean the furnace.

Yea, quite a piece of work, this professional electrician. But you keep on defending him so we get a good idea of the quality of your work and your professional standards.

Last edited by diycc2; 01-04-2017 at 08:48 PM.
diycc2 is offline   Reply With Quote
Old 01-04-2017, 09:04 PM   #15
Electrical Contractor
 
jbfan's Avatar
 
Join Date: Jun 2004
Location: Newnan GA
Posts: 6,772
Rewards Points: 138
Default

Re: Installation For 120v Generator Feed -- How To Split 3-Wire Romex Fed "Dual Circu


Quote:
Originally Posted by diycc2 View Post
Really? I think not.

First of all, the electrician was told that we would, in the future, be installing a generator. Of course if this "electrician" had an IQ north of 100, he would not have inextricable tied a number of circuits together knowing that there was at least a possibility of the installation of a mini-load center with segregated circuits. Secondly, it is both stupid and dangerous to use a shared neutral -- do you know why? Thirdly, this lazy dimwit used standard breakers just to make sure he put some innocent party at risk (do you know why that's a risk -- hint it relates to turning off one breaker while the other breaker feeds the shared neutral?).

Finally, this brain surgeon made other lazy-azz blunders like attaching the recirculating pump controller box (electronics) to the sheet metal covering of the hot water boiler -- this would not only fry the electronics over time, it also prevented removal of the cover in order to clean the furnace.

Yea, quite a piece of work, this professional electrician. But you keep on defending him so we get a good idea of the quality of your work and your professional standards.
Can't help you made a poor decision in picking your electrician.

Advertisement

__________________
"The problem isn't that Hillary Clinton lies. We all know she lies. The problem is that her supporters don't seem to care"
jbfan is offline   Reply With Quote
Reply


Thread Tools
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
romex with thin grounding wire dogbone Electrical 16 01-10-2009 09:40 PM
Neutral Wire? 4x15mph Electrical 8 11-24-2008 02:00 PM
hooking up dryer....bronx ny code SURFBUG Appliances 6 10-14-2008 10:41 PM
Dimmer Installation rjl24 Electrical 4 02-20-2008 08:43 PM
Bonding (bond wire) & Spa Installation on existing concrete pad crusius2 Electrical 1 11-14-2007 01:00 PM




Top of Page | View New Posts

 

Search Engine Friendly URLs by vBSEO 3.6.1