Backfeeding generator through UR feed to shop

[wcp0611]

Can someone take a look at my little doodles and tell me if any of this is a possible code violation? Right now, my shop is fed off of 1/0 URD triplex coming from a 100amp breaker at my house. Its a little over 160ft away. I have been wanting to add a diesel generator for backup power for occasions that call for it.

My current set up is:

The 400 amp service comes in my meter and runs out to two main disconnects on each side. My house is fed by the left disconnect and my shop is fed by a breaker in the right disconnect. It was installed this way to minimize any dimming lights in my home if the shop compressor or welder is being used as I had that happen a lot when I had 200amp service to my home.

The first pic is my current setup and second pic shows how I foresee wiring to go. The addition of a polaris splicer in the right disconnect which allows power from the house to the shop and at times when our power is out, would allow power from the shop to feed the main panel. Is this against code or are their any issues with this setup? Obviously, this would require me to flip the necessary breakers to allow for the shop backfeed to not allow power to the incoming wiring from the transformer, which is fine with me as I think the two to three times a year we go more than a day without power would not be so bad to go walk around flipping three or four switches.





TO

 

[Innovate1]

No way this is acceptable. There is no interlock to prevent backfeeding the utility and just you flipping breakers off is in no way acceptable. And the connection between panels looks problematic too. Prepare to hear the same from many here. Just because it works doesn't mean it is safe or correct.

 

[wcp0611]

Okay, let's say I add an interlock to both main disconnects at my house. Does this work then? I'm okay with criticism. Lord knows I'm not an electrician.

 

[mike93lx]

Nope. Needs a separate line back to the main, also needs to be 4 wire.

How long ago was that triplex run?

 

[wcp0611]

Nope. Needs a separate line back to the main, also needs to be 4 wire.

How long ago was that triplex run?

The triplex was ran maybe seven years ago. Why?

 

[mike93lx]

The triplex was ran maybe seven years ago. Why?

Because 3 wire subpanel feeders were prohibited in the 2008 code cycle

 

[wcp0611]

Because 3 wire subpanel feeders were prohibited in the 2008 code cycle

Well, codes pass me on it. I ran two ground rods at the sub at the shop and the house already had two ground rods.

 

[wyliesdiesels]

Okay, let's say I add an interlock to both main disconnects at my house. Does this work then? I'm okay with criticism. Lord knows I'm not an electrician.

no that wont work either. the interlocks prevent 2 breakers from being on at the same time (utility and generator). there isnt room in each disconnect for more than 1 breaker I assume and also, you dont have a separate feed for the generator from the shop so how would you get utility power to the shop when the interlock has that feed locked out? you cant run bi-directional power (utility and gen) on a feeder that has an interlock on it (your diagram shows arrows going in both directions)

the only way to make this work is to run a separate 4-wire feeder from the gen to the house, get a service rated transfer switch to go between the meter and the 2 disconnects or change the disconnects so they have 4 spaces or more and add interlocks on both. you would then need to jumper the feeder from the generator between both disconnects.

what you propose is not electrically possible

 

[wyliesdiesels]

Well, codes pass me on it. I ran two ground rods at the sub at the shop and the house already had two ground rods.

its totally 100% WRONG. whoever inspected that is a *****.

ground rods are a different animal than the EGC required in the feeder.

see post #3 on FAQ sticky

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Also URD is not allowed inside a building unless its dual rated. most is not

 

[Zeke]

Well, 7 years ago was circa 2016. Hard to imagine you weren't on the 2011 code at least. But recent searches have shown me that some counties, not states, are still using some pretty dated versions of the NEC. So, if you don't mess with it, it's OK. Once you do that proposed work you need to follow your current AHJ's code.

All this in spite of it not being viable according to the experts here. And I say this not knowing old codes and what you did then vs what you did not. Possible the inspector was a *****. Wouldn't be the first.

 

[cycle61]

what you propose is not electrically possible

Oh, it's electrically possible, just illegal and not possible with residential/commercial grade devices.
This room has six independent supplies feeding dozens of loads, with multiple reversible power flow paths, and can transfer automatically between any combination of them.
But I doubt our OP wants to pay the kind of money this requires.

 

[wcp0611]

Oh, it's electrically possible, just illegal and not possible with residential/commercial grade devices.
This room has six independent supplies feeding dozens of loads, with multiple reversible power flow paths, and can transfer automatically between any combination of them.
But I doubt our OP wants to pay the kind of money this requires.

Haha absolutely not!

 

[wcp0611]

its totally 100% WRONG. whoever inspected that is a *****.

ground rods are a different animal than the EGC required in the feeder.

see post #3 on FAQ sticky

Electrical FAQs

Welcome All I have started this sticky as an FAQ thread for info on the basics that are encountered countless times every week on here. Hopefully this will help some. If u have a topic request, go ahead and post it. And if you have an FAQ you would like covered let me know.... Or if you...

www.garagejournal.com

Also URD is not allowed inside a building unless its dual rated. most is not

Welp, I'm a liar. Went out and checked and I did run a a four wire to the shop. It's been seven years. I forgot.

 

[wcp0611]

The arrows in the diagram were just to help show the distance. They weren't electrical direction.

 

[dcg9381]

I have a similar setup. I have a 320A service that splits to the home and to the shop.
You can't do what you want to do and have it be safe, legal, or code compliant.

You have to do what I do, generator for the house, generator for the shop.
For each of those generators you need and ATS or you need an interlock.

 

[mike93lx]

I have a similar setup. I have a 320A service that splits to the home and to the shop.
You can't do what you want to do and have it be safe, legal, or code compliant.

You have to do what I do, generator for the house, generator for the shop.
For each of those generators you need and ATS or you need an interlock.

You could do this with one generator.

Interlock with an Inlet at one panel, then run a breaker in that panel with a feed to an interlock in the other panel.

 

[Innovate1]

You could do this with one generator.

Interlock with an Inlet at one panel, then run a breaker in that panel with a feed to an interlock in the other panel.

Interesting idea. I hadn't thought of that. I have generator feed to one panel with most of the important loads on that panel. If I discover some needed loads on the other panel I might do this.

 

[mike93lx]

Interesting idea. I hadn't thought of that. I have generator feed to one panel with most of the important loads on that panel. If I discover some needed loads on the other panel I might do this.

I went through this with my 320a service and decided to just move a couple things over to one panel like you are doing too. But with a shop and house, that's a little harder.

That said, depending on proximity, two generators could be a hell of a lot simpler and avoid running back and forth to flip breakers

 

[Innovate1]

I went through this with my 320a service and decided to just move a couple things over to one panel like you are doing too. But with a shop and house, that's a little harder.

That said, depending on proximity, two generators could be a hell of a lot simpler and avoid running back and forth to flip breakers

I had the generator interlock on a subpanel with just a few loads but decided to move it to the main panel that feeds that. I was fortunate that it was the same panel that feeds the shop so I can now run furnace and some other loads in both buildings.

 

[dcg9381]

You could do this with one generator.
Interlock with an Inlet at one panel, then run a breaker in that panel with a feed to an interlock in the other panel.

Doesn't that count as "dual service" (or whatever the NEC term is) even with an interlock? I know there are allowable exceptions.

That design would be functional and safe.

I dont know the OPs case, but there is probably a reason service was split at the meter. In my case, running 320A to the house, then another 100A or so down to the shop is a lot more wire than splitting it from the meter.

 

[mike93lx]

Doesn't that count as "dual service" (or whatever the NEC term is) even with an interlock? I know there are allowable exceptions.

That design would be functional and safe.

I dont know the OPs case, but there is probably a reason service was split at the meter. In my case, running 320A to the house, then another 100A or so down to the shop is a lot more wire than splitting it from the meter.

Since only one line could be active at a time, I'd think it would be ok, but I am far from an expert.

I'm not advocating for the approach, though, and would likely run two generators if it was me, especially if it was a shop. Doesn't take much power to run some lights and keep the beer fridge cold

 

[P0234]

Another option if you are fine with the generator being at the house is one of the generlink units, they fit between the meter base and the meter and will just power everything you want. Unfortunately not too many PoCos like them, mine used to offer them but then became wankers about them when they started referring people for whole house generator kits through some affiliated party.

 

[dcg9381]

Since only one line could be active at a time, I'd think it would be ok, but I am far from an expert.

I think it's covered in National Electrical Code (NEC) Section 230.2 states that a building or other structure served shall be supplied by only one service. Goes on to specify that this has to do with "wires", so basically bringing in two sources of power is generally prohibited.

There is an exception for "standby" systems, but I don't know that anyone has successfully argued in residential-land with an electrical inspector that has been taught forever that residential/shop can only have one source of power. I've argued that it might be acceptable in residential when used for backup, but I think it's an oddball case.

I'm not advocating for the approach, though, and would likely run two generators if it was me, especially if it was a shop. Doesn't take much power to run some lights and keep the beer fridge cold

Other than cutting 200' of rock for another line, I realized the reason I don't do it this way is that the shop had solar and I have to lock out not only the grid, but the solar system, which was complicated at the time. If I had to do it today, I'd just buy a modern solar inverter that has a generator feed and is essentially an ATS with grid/generator capability... Not sure it gets you around 230.2 though.

 

[wcp0611]

So, back to my first post, if I put the 100amp breaker for the shop in the left panel that feeds the house as well, could I backfeed power from the generator at the shop to the house panel? To clarify, I'm not looking for power at the shop if the lines are down. I'm just looking for power to feed from the generator to the home panel to power the house and leave the shop out of the equation.

If so, I'd have to splice the shop wiring from the right panel through the t-conduit coming from the meter, to the left panel. Is it against code to run more wiring from through that conduit given the poco tagged/locked it after inspection?

 

[mike93lx]

You need a new wirw back to the house to carry the generator power. You can't do this over the existing feeder and it will not connect to the shop. The shop would be fed from the breaker in the main

Think of it as using a really long cord and you are just locating the generator at the shop instead of at your house

 

[Innovate1]

So, back to my first post, if I put the 100amp breaker for the shop in the left panel that feeds the house as well, could I backfeed power from the generator at the shop to the house panel? To clarify, I'm not looking for power at the shop if the lines are down. I'm just looking for power to feed from the generator to the home panel to power the house and leave the shop out of the equation.

If so, I'd have to splice the shop wiring from the right panel through the t-conduit coming from the meter, to the left panel. Is it against code to run more wiring from through that conduit given the poco tagged/locked it after inspection?

No way to do an interlock and both feed the shop and (at a different time) backfeed power from the generator at the shop to the house. You would need another cable between the shop and house.

 

[wyliesdiesels]

No way to do an interlock and both feed the shop and (at a different time) backfeed power from the generator at the shop to the house. You would need another cable between the shop and house.

bingo.

 

[wyliesdiesels]

So, back to my first post, if I put the 100amp breaker for the shop in the left panel that feeds the house as well, could I backfeed power from the generator at the shop to the house panel? To clarify, I'm not looking for power at the shop if the lines are down. I'm just looking for power to feed from the generator to the home panel to power the house and leave the shop out of the equation.

If so, I'd have to splice the shop wiring from the right panel through the t-conduit coming from the meter, to the left panel. Is it against code to run more wiring from through that conduit given the poco tagged/locked it after inspection?

the interlock would prevent the shop breaker from getting power from the PoCo when the generator is not in use.

its not possible to do what you want with what you have. need to run a new wire