Generator with grid-tied solar PV system

[micah]

Hi, have searched but haven't found an answer about my same setup.

I have a 7KwH system w/ Suniva panels and microinverters. As far as I can tell, all this is true:
-Power all feeds into a grid cutoff outside the house which opens the circuit in a power outage
-From the shutoff, the power feeds into the basement
-There it goes through a breaker for each of the 2 arrays, and then "backfeeds" a 220V breaker in the panel

So, next I would like to be able to use a small portable backup gen (Honda EU2000i) to power either furnace or refrigerator, and a few lights. My situation will be 100V only. I have 2 possible ways of doing this:

1) A generator interlock switch such as https://www.ebay.com/i/172244594942?chn=ps. Here power is backfed to a breaker from a gen cord to a socket on the exterior of the house. That gen breaker can mechanically only be on if the main breaker is off. In this case, during an outage, I'd turn off all the circuit breakers in the panel, flip the main, flip the interlock, fire up the gen, and then flip on only the 1-2 breakers I want to use. Because I'm only feeding 110V, I'd need all my "emergency" breakers on the same leg of the panel, eg every other breaker on the right side. Easy enough to set up.

2) A small gen transfer panel like http://a.co/ebmf4JY, where the panel puts a switch for line-off-gen inline into each circuit you'd want to use in an outage. More to wire, but also no big deal.

I would like to do #2 to isolate the gen to the separate panel, because it seems more accepted, and to avoid having to flip all the breakers off/on. I just want to make sure that either of these options is okay w/ 220V of solar coming into the main panel.

And, in both cases, what happens if the power comes back and I have the gen running?

Thank you!

[sdold]

Hi micah, thanks for joining and welcome to Solar Panel Talk. Your post didn't show up right away because it had a couple of links, which are not a problem, but the forum flags them for moderation because spammers often throw out links in their first post. Good luck with your system and I'm sure you'll get some good advice shortly.

Steve

[Sunking]

Well being an engineer I can only say there is no code compliant and safe way. Neither option 1 or 2 would ever pass inspections and extremely dangerous.

[micah]

Sorry, having trouble editing. Apparently this forum does not like my apostrophes?

Sunking - thank you for your reply. I see you are the man for answers on this forum and I appreciate any help. Especially as I am new here, having been invested in solar for years but only now having found this forum.

Let's leave #1 out of the options. I would like to have a MTS anyway as it is the expected setup and does not require me to turn off all the other breakers to use the gen.

For my own reasoning and in case I was unclear last night, here is how I would use a #2 MTS setup:
-I would use the MTS I linked to above. It is only 6 circuits and 5,000 watts but that is plenty for my needs. In fact, I am only going to wire this MTS as 110V per the output of the inverter gen, but that does not matter here.
-The MTS will mount next to my single 200A GE load center. I will remove 3-4 critical loads from their LC breakers and route them through the transfer panel using the MTS pigtails. Ignoring solar, these transfer circuits will now be switched by both the MTS and the orig breaker.
-The MTS will be fed by a portable gen outside, with a cord to a socket on the house. That socket wires to the MTS.

Then there is the PV backfeeding into the LC through a 220V breaker. This was installed as usual with an auto disconnect in case of power outage, to protect utility workers. I have no interest at the moment in using my PV during an outage, although I understand why people would want to. Last time we lost power it was for three days, and 2 of those were bright and sunny!

Scenarios:
A) Grid is on: SOP here of course. Gen is in the shed.

B) Grid goes down, the PV system auto disconnects from my LC. Start up the gen. Flip whatever transfer switch circuits I want to use from line position through off to gen. The MTS has disconnected the generator backed up circuits from the building main AC power and routed them to the gen side instead.

C) 1-2 circuits are running on gen after B above. Grid comes back on. This is where I have Qs. As far as I know from the MTS setup, it seems clear that the grid will now power everything EXCEPT the circuits I have switched to gen. Whenever I want, I switch those loads back to grid and then shut off the gen.

Hope this makes more sense and again appreciate the input. Cheers, all.

[Sunking]

Sunking - thank you for your reply.

You are welcome although I did not tell you anything. I am not saying you cannot make it work because you could make it work. . What I am saying is there is no safe way to do what you want and I will not help you do that. To start with the Honda Generator cannot be used to interconnect with your home wiring. It is just not designed or listed for such purpose. Second is you cannot backfeed your home wiring with Plug-n-Cord as you described. In other words I am not going to help you hurt yourself. There are plenty of idiots here and on Youtube who will help you out with that.

Now if you want to do this safely by code I will help you. To do that will require a Genny made for such purpose and a proper Transfer Switch. Otherwise I cannot help you.

Merry Christmas and God Bless.

[micah]

You may well have the same opinion after reading my actual response, which got cut off. But seeing your objections, just a couple things to consider.

Let us start outside. In my state gennies do not need to be hardwired. Portable to transfer switch to load center or panel is fine. I know this gen will only provide 2000 watts of 110 and that is all I need. I chose it in general for clean quiet power. I will not use a male to male suicide cord, I will run a 8-gauge weatherproof extension cord from the gen to the dedicated male socket on the house. This is like using any other portable gen to go to a house power input socket.

Inside, the back of the house input will run properly with less than 6 feet of 8 gauge romex to the transfer switch. Again, as usual.

I assume you do you not have any issues with manual transfer switches in general, since I have seen you recommend them in other posts. So I will stop there.

I hope this helps!

[Sunking]

Let us start outside. In my state gennies do not need to be hardwired.

No state requires the genny to be hardwired or pad mounted. Portable generators can be used, but the Generator must be made to do so, and code must be followed. Example use a Generator Snout using a SO Power Cable. AKA Appleton plug and receptacle with a Transfer Switch.

[Sunking]

And, in both cases, what happens if the power comes back and I have the gen running?

Well that is where code comes into play and why a Transfer switch must be used. A Transfer Switch is what disconnects and isolates you from the Utility and your solar system. Not necessarily for your protection, but to protect utility workers and your neighbors from you and your generator.

To answer your question if you had the generator connected when the utility power comes will let the magic smoke out of the generator, vaporize your wiring, and a nice fireball for you to play and have fun with.

So my only answer to you is going to be is hire a pro, have them pull permits, and pass inspection. If you do this, and anything goes wrong, you are liable for all property and injuries with absolutely no defense. Your HO insurance policy would be worthless for property damage and any injury or death would be criminal offense of involuntary manslaughter just like driving drunk. Follow the rules and your butt is covered.

Sorry I know that is not what you wanted to hear, but the only answer I can give you.

[JSchnee21]

Given how small the generator is, and how few the loads. Heavy duty (8-gauge as I have fairly long runs) extension cords seem like the best solution (which is what I'm currently doing). But, with a larger portable generator (6kW to 10kW) and a professionally installed manual transfer switch like this one (see below) you can certainly be code compliant.

30 Amp 240VAC input

https://www.electricgeneratorsdirect.com/Generac-6382/p9478.html

50 Amp 240VAC input

https://www.electricgeneratorsdirect.com/Generac-6335/p9479.html

The main issue from my perspective is phase balancing across the two split phase legs in you load center. Smaller portable gennies don't tolerate the two windings (one per split phase when running in 240V mode) being out of balance by more than ~30% or so. The governor will try and modulate the engine RPM to maintain the proper voltage and one of the windings will either be too high or two low.

My portable is 6500kW and I would love to not have to use the hundreds of feet of extension cord I use to temporarily power loads all over my house. But, at only ~24 to 27 amps continuous per phase, it's not really big enough to run my load center (obviously AC is turned off, etc.) without careful monitoring of the phase loading. Using extension cords, and by switching to 120V output, both windings are wired in parallel so no concern over phases. BUT, I cannot power the load center in this configuration -- hence extension cords.

A stationary 1800rpm natural gas gennie would be great, but at ~$10-20K installed, a bit to rich for me at present. Perhaps when my cryptocurrencies continue to appreciate further. (-:

[micah]

Well that is where code comes into play and why a Transfer switch must be used. A Transfer Switch is what disconnects and isolates you from the Utility and your solar system. Not necessarily for your protection, but to protect utility workers and your neighbors from you and your generator.

To answer your question if you had the generator connected when the utility power comes will let the magic smoke out of the generator, vaporize your wiring, and a nice fireball for you to play and have fun with.

I definitely wouldn't do this without a transfer switch. I can certainly see why pitching the grid and my generator in a head-to-head cage match would be a problem! LOL.

Why do you seem to think I'm not using a transfer switch and a proper gen inlet box? Maybe those links aren't working in my first post.

1) I am using a very highly rated MTS: Reliance Controls Corporation 20216A Pro/Tran 6-Circuit Indoor Transfer Switch for Generators Up to 5,000 Running Watts
Link that may work: Reliance Controls Corporation 20216A Pro/Tran 6-Circuit Indoor Transfer Switch for Generators Up to 5,000 Running Watts.

2) I'm also using an approved alternative to your snout, in my case a dedicated generator inlet box by Leviton.

Seems like these items would change your answer? If not, I guess I don't understand and will move on. Cheers and thanks for your time.

[micah]

One more thing, happened to see this video, shows exactly what I'm doing but he uses a 4-circuit switch.

The only issue I see with this plan is if someone somewhere can show me proof that you can't use a 110V inverter gen, or this particular gen, to power house circuits. But I see no reason that would be true, electrically speaking. 1,600 watts of clean 110V power will run what I need, and I'm using approved ways of routing it to the circuits.

Cheers.

[Mike90250]

With small portable generators, grounding to the building electrical ground is often the issue, getting a transfer switch that properly manages the Neutral and Ground wires too.

[Sunking]

One more thing, happened to see this video, shows exactly what I'm doing but he uses a 4-circuit switch.

The only issue I see with this plan is if someone somewhere can show me proof that you can't use a 110V inverter gen, or this particular gen, to power house circuits. But I see no reason that would be true, electrically speaking. 1,600 watts of clean 110V power will run what I need, and I'm using approved ways of routing it to the circuits.

Cheers.

Simple your genny is not made or listed for Premises wiring systems. Like Mike said bonding is the issue and that genny has the grounded circuit conductor and frame bonded together with no means to separate them. Sorry I cannot help you. Like a doctor, I am not going to tell you to smoke.

That generator is made to do one thing only, be portable and power Plug-N-Cord equipment like a toaster, lamp, or fridge with an extension cord.

[micah]

With small portable generators, grounding to the building electrical ground is often the issue, getting a transfer switch that properly manages the Neutral and Ground wires too.

Thanks, Mike. This helps a lot. Then here we go. Problem solved with a MTS that transfers the neutral too. I only need 3 circuits, so this will be cheap and easy.

Cheers.

[micah]

With small portable generators, grounding to the building electrical ground is often the issue, getting a transfer switch that properly manages the Neutral and Ground wires too.

Mike - Actually, and this is very unusual, but it turns out the Honda EU series DOES have a floating ground (which is unusual for a small portable). So the typical Pro-Tran MTS above that does not switch neutral will work just fine. I will just need to sink a rod where I will run the gen, as anyone should. The MTS company has confimed this, and approved the 110V use as well. Thanks again.