[JonCiccarone]

Hi there,

I had a new question come up regarding a project mentioned in a previous post.

I'm looking to install a generator setup at my in-law's. The goal is to power the main house panel and also the panel on the rental cottage on the property. The two houses are on two separate services from the electrical company.

I've worked out all the kinks regarding sizing of generator/circuits, voltage drop, etc. But the one question I can't wrap my mind around is: How do I split the neutral coming from the generator?

The initial generator switch box (with a 30 amp main breaker from the generator, and a double-pole breaker to each house panel) currently has 2 different neutrals coming in from the two respective houses. How would I wire this so that I’m not connecting the 2 different services’ neutral bus bars together? Because I’m aware that violates code. The generator feed only has one neutral coming from it - how do I split that to go to both houses? Or, if I can't, am I risking anything by having the rental cottage not connected to the generators' neutral? I believe both houses have shared neutral/ground bus bars.

TIA,
JC

 

[seharper]

I certainly hope you are providing the mandatory generator interlock, especially given that at least one of the houses are for people not you, who are unlikely to follow any written procedures in a crisis. You really don't want to be connected with a lineman fatality.

You are correct; you have identified the fatal flaw in your design.

There are a couple ways to do this. One involves the generator feeding a transformer to one of the subpanels. The reason I suggest this one is that it's cheap; a common 5 KVA transformer sometimes seen on Craigslist for as little as $100. Wire the 240/480 side for 240V (which you feed from the main house panel) and the 120/240V side for split-phase which goes into the cottage's interlock. If it's a 5 KVA transformer, protect it with a 20A breaker at the interlock.

The other way is to go upscale on transfer switches, and get one that switches the neutral. This would need to be one that switches the full utility load on one side, so it'll be a biggie. You could smuggle a couple of neutral-switching generator panels from Canada; they basically do the breakers-across-from-each-other interlock trick, with a 3-pole breaker at the top position, and the 3rd pole clips onto a special bus stab that is for neutral. Slick as a whistle, but UL and CSA will only put a "C" (Canada) endorsement, not "US".

 

[JonCiccarone]

I certainly hope you are providing the mandatory generator interlock, especially given that at least one of the houses are for people not you, who are unlikely to follow any written procedures in a crisis. You really don't want to be connected with a lineman fatality.

Thanks for the reply. Both the panels will have standard generator interlock setups. The rental is a short-term (airBnb) and in the event of a power outage, my father-in-law would be dealing with the switchover, so no risk there.

What would happen if the cottage panel wasn’t tied to the generator’s neutral and only was fed hot wires from the generator? Would it still work safely if it was only relying on it’s regular neutral/ground bus bar? Not quite sure how that works.

Asking because this transformer idea seems a bit outside my pay grade. And smuggling a panel from Canada isn’t an option, especially while the border is still closed.

JC

 

[dmxtothemax]

You say the power feed for both propertys are seperate ?
How far apart physically are they ?
Are they close together at any point ?

 

[AllanJ]

Do not run just the generator hots someplace and omit an accompanying neutral.

As a point of information, at each service panel a combined neutral and ground which is often a messenger (support) wire for the hot feed conductors as well goes back to the utility pole where it is connected to the utility pole pole-to-pole ground and pole transformer neutrals.

 

[oldelectricguy]

>>What would happen if the cottage panel wasn’t tied to the generator’s neutral and only was fed hot wires from the generator? Would it still work safely if it was only relying on it’s regular neutral/ground bus bar? Not quite sure how that works.<<

It doesn't work. Please hire a competent electrician before you injure or kill someone. What you want to do is NOT a good idea.

 

[JonCiccarone]

Well, looks like I'll have to go back to the drawing board on this one. Thanks to all for the feedback.

 

[rjniles]

I do not believe there is a safe compliant way to use 1 generator to power 2 services.

 

[JonCiccarone]

The other way is to go upscale on transfer switches, and get one that switches the neutral. This would need to be one that switches the full utility load on one side, so it'll be a biggie. You could smuggle a couple of neutral-switching generator panels from Canada; they basically do the breakers-across-from-each-other interlock trick, with a 3-pole breaker at the top position, and the 3rd pole clips onto a special bus stab that is for neutral. Slick as a whistle, but UL and CSA will only put a "C" (Canada) endorsement, not "US".

Are the attached links what you're referring to? I'd love to get my hands on one of these panels in California but I'm having a hard time finding any retailers that stock them. I'm revisiting this idea, and it seems like this panel would solve all of my issues?

http://www.reliancecontrols.com/ProductDetail.aspx?XRC1003CR
https://www.amazon.com/Reliance-Controls-3-Pole-Transfer-XRC1003CR/dp/B00PPCDXJS

Thanks,
JC

 

[seharper]

Are the attached links what you're referring to? I'd love to get my hands on one of these panels in California but I'm having a hard time finding any retailers that stock them. I'm revisiting this idea, and it seems like this panel would solve all of my issues?

http://www.reliancecontrols.com/ProductDetail.aspx?XRC1003CR
https://www.amazon.com/Reliance-Controls-3-Pole-Transfer-XRC1003CR/dp/B00PPCDXJS

Thanks,
JC

By golly, that is the sort of thing I'm talking about. Except these were made by top tier makers and had more spaces.

 

[Blue Marjan]

I do not believe there is a safe compliant way to use 1 generator to power 2 services.

This is scary. I pulled the permits & passed the inspections to run an aux-power system, and each of my buildings has its own interlock transfer switch. The aux power system is four wires, in conduit, underground.

I'll have to take some pix and start my own thread to examine this!

 

[JonCiccarone]

By golly, that is the sort of thing I'm talking about. Except these were made by top tier makers and had more spaces.

I communicated with a guy from Reliance Controls, and it looks like they discontinued their XRC Series that I attached in my previous reply and replaced it with a new series called XRK. They make 3-Pole Neutral-switching panels with 6 spaces all the way up to 26 spaces, and should ship anywhere in the US.
See link: Transfer Switch Catalog - Reliance Controls Corporation

Any reason I couldn't use that for my intended setup?
Thinking of getting the 10 space panel and using it as a subpanel at the main house with dedicated generator circuits. I'd be switching those 10 circuits from the main house onto generator power and thus the cottage's neutral system whenever the generator is in use.

JC

 

[JonCiccarone]

Anyone see any reason to not do this? Thinking I'll place the order this week.

Thinking of getting the 10-space neutral-switching panel and using it as a subpanel at the main house with dedicated generator circuits. I'd be switching those 10 circuits from the main house onto generator power and thus the cottage's neutral system whenever the generator is in use.

Found an online supplier here: https://www.dale-electric.com/products/view/GEN XRK1003DR

Catalog from Reliance (with description): http://reliancecontrols.com/Catalogs/transfer-switches/?page=50

JC

 

[seharper]

Anyone see any reason to not do this? Thinking I'll place the order this week.

That type of panel is a great design/approach (basically like the Canada panels I mentioned)... only thing that rubs me wrong is a) it's so few spaces, and b) those suppliers notoriously overcharge for what the item is.

You could also consider a plain a-la-carte 3PDT transfer switch, i.e. *just* a switch and have that feed any ordinary subpanel.

 

[JonCiccarone]

That type of panel is a great design/approach (basically like the Canada panels I mentioned)... only thing that rubs me wrong is a) it's so few spaces, and b) those suppliers notoriously overcharge for what the item is.

Thanks for that, that's encouraging. I'm choosing the 10-space panel because I don't want to replace the whole main load center (with attached meter), plus it has tandem capability for up to 18 circuits. They do make full-size panels, I'd just rather single out the ones I need. The cost is a bit high, but seems to be the only product of it's kind.

You could also consider a plain a-la-carte 3PDT transfer switch, i.e. *just* a switch and have that feed any ordinary subpanel.

I thought about something like this, like using a 3-way switch to switch the neutral system over. I just can't think of any way to safely interlock this so that nobody forgets to switch the neutral system back after the power is back on.
Would love any further ideas on this, but I think my default is buying one of the aforementioned panels! :thumbsup:

JC

 

[seharper]

Thanks for that, that's encouraging. I'm choosing the 10-space panel because I don't want to replace the whole main load center (with attached meter), plus it has tandem capability for up to 18 circuits. They do make full-size panels, I'd just rather single out the ones I need. The cost is a bit high, but seems to be the only product of it's kind.

More spaces are always good, but don't pay nosebleed prices for em. If you need more than they want to give you at sane cost, you can always extend off it to another subpanel.

I thought about something like this, like using a 3-way switch to switch the neutral system over. I just can't think of any way to safely interlock this so that nobody forgets to switch the neutral system back after the power is back on.

Exactly. They need to be hard-interlocked so it is mechanically impossible to leave them in a misconfigured state, and what's more, this interlocking must be UL-approved, so it's not permissible to wing-ding it with Bowden cables or whatever. I was thinking industrial 3-phase switches, like an A/C disconnect but with an extra blade (and double throw of course).

 

[JonCiccarone]

If you need more spaces than they want to give you at a sane cost, you can always extend off it to another subpanel.

That's a good point!

I was thinking industrial 3-phase switches, like an A/C disconnect but with an extra blade (and double throw of course).

Well if you're aware of any products like this available in the US, would definitely love to hear about it. But I think I'll place the order for this neutral-switching panel in the next couple days. What a cool product. None of the distributors around here have ever heard of such a thing. :vs_laugh:

 

[seharper]

Yeah, that xfer switch is sweet.

Here's what I mean by a 3-pole double-throw. They're made for switching generators on 3-phase, but you just use one of the poles for neutral. Sadly they are priced for 3-phase too.

 

[Jim Port]

You are going to try and run two building off of 30 amps total?

 

[JonCiccarone]

You are going to try and run two building off of 30 amps total?

It's all LED bulbs and gas appliances in both houses. Will be keeping unnecessary circuits turned off and not using any electric kitchen stuff (microwave, toaster, etc.). The biggest things are the shared well pump, and refrigerators. Wiring the whole system so that the generator can be swapped out in the future for a bigger (50A) one.

Just trying to be able to see in the dark, charge devices, have internet on, keep water running, and prevent food from going bad.

JC