Can you connect an inverter to a single circuit in your house?

Heya folks!

So I posted on Reddit and got a little bit of information and some resources but i really should have started here. In short, I'm wondering if you can tie an inverter to a single circuit in your house and not the whole panel itself. Possible?

Thanks to Will, I've been tinkering with the idea of placing some panels in my backyard , buying a smallish 24 volt inverter/charger (MPP most likely) and small battery pack (2.4kW) and placing that in my garage to charge my tools, e-bike and other stuff out there. But than I thought, no way would I use ~2000 watts a day out in the garage. I'd love to tie it into one of my existing electrical circuits that runs some basic lights, computer, tv etc. If I tied it to my whole panel, it probably wouldn't last very long. Is this at all possible or a pipe dream? I'm somewhat familiar with off-grid systems, but I no idea how it ties to a grid or what components are required.

I'm consider the MPP solar invrter as mentioned but unsure if I need an off-grid or hybrid version.

I'm not entirely new to basic electrical (just rewired my garage) but certainly green to solar. I'm just wanting to get my feet wet with solar and batteries (want to build one later) so this is a project/hobby to just gain some experience. Thanks for all who read this novel!

Do you mean permanently, or do you want to be able to switch the circuit from grid to the inverter and back?
Permanently disconnecting the circuit from the breaker panel and having the circuit be powered full time by the inverter is the safest approach.

Fred S said:

Do you mean permanently, or do you want to be able to switch the circuit from grid to the inverter and back?
Permanently disconnecting the circuit from the breaker panel and having the circuit be powered full time by the inverter is the safest approach.

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Hey, thanks for the reply!

It would be nice for it to auto transfer, but if I had to manually switch it that wouldn't be the worst thing in the world. My concern is that I'd also be back feeding the grid (potential to electrocute someone), although a friend of mine says that's a non-issue. I do have a spare 240 volt dryer line that's never used. Would it be possible to power my whole panel using that and a kill switch between them? I think my whole house would eat up 2000 watts in about 3-4 hours (no AC, single bachelor pad).

I agree, back feeding the grid with a 2k inverter is going to pop the inverter (whether burning it up or blowing a fuse). Auto transfer is some work and money.

It is best to do it the right way through the permitting process; but buying a "hybrid inverter" you could separate out some circuits to a separate panel and power that stuff. A hybrid inverter would switch those circuits back to be powering off the grid when the battery ran out.

If you are looking at just saving money and not backup, just do a standard solar install with a grid tie inverter and legally back feed the grid after getting the power companies approval.

Jlomb436 said:

...It would be nice for it to auto transfer...

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A number of inverters have an ATS built in and are designed for exactly this purpose. Typically you want a charger built in too so everything is automatic.

Here's an example link to the first one that came up on google https://www.aimscorp.net/2000-Watt-Pure-Sine-Inverter-Charger-UL.html, you'll have to shop around for the best price/quality. You might check AltE, they generally only sell good quality equipment so you might get some ideas there.

My approach is to feed a subpanel and add circuits to that to run off of solar/inverter. It won’t take too many to hit the limit of your inverter.

For safety sake these circuits will be completely separate from and have zero chance of back feeding the grid.

It is critical to NEVER back feed the grid unless you want to take on a proper grid tie system which is a whole other kettle of fish.

For another ATS option watch Will’s video that I posted at the top of this thread:

Take a look at the Reliance transfer switch, they are used for powering circuits from a gas generator but can be used with solar. It gives you the separation from the grid and control as to what circuits you want to power with solar. You just plug the inverter into the transfer switch and flip the switches from grid(line) to solar (gen). I have a 6 circuit switch wired into my main panel and can power them with my gas generator or from my solar inverter. I can pick which circuits to power depending on the load and how much power I have stored in my batteries.

If you don't use a transfer switch, another approach - and I can't speak to code - is to use a 20+ amp rated DPDT switch. The inverter and grid hot legs each must have a max 20 amp breaker or fuse, but preferably a 15 amp. The grid neutral and hot wires would be on one input, the circuit (the outlets) would be on the "center" two poles, and the inverter neutral and hot would be on the other input. Only one input would be connected to the target circuit at a time, and so the grid and inverter can't "short" together. The ground wire for the target circuit should stay tied to the house's ground.

The DPDT type switches (at least in the "household wall switch" style) cost a fair amount more than a SPDT type (aka a "3-way" wall switch). Yes, you could use two 3-way switches side by side and mechanically connect their two toggles together.

Without using a transfer switch, there are safety issues (notably overloads and fire) if inverters are improperly wired to home circuits. I recommend you try to get instructions from the inverter manufacturer for this -- to make sure all wires (including grounds) are correctly installed and are of sufficient gauge.

So I was planning on using an MPP (model LVMK2000 watts) or a Growatts 3000TL LVM that does have an ATS built in (I think) and a charger. I'm just not sure how to safely feed the panel. The more I think about this, I might just feed the whole house vs a single circuit. My usage is relatively low so it wouldn't be too bad.

How would I wire this so? Just run a line to an useused breaker on the panel? I'm just figuring out though, that the inverter is 120 volts. To power the whole panel, I'd need one that produces 240 volts right? Otherwise, 120volts to a breaker would only power one line of 120, the other side would not be powered, correct?

PS, I'm still learning. Not new to electrical, but certainly green and to solar as well. Just trying to learn and pick up a new hobby. Thanks!

JoeHam said:

For another ATS option watch Will’s video that I posted at the top of this thread:

Need basic relay advice

I have noticed there are two basic types of folks on the forum. Those who wish you would just blurt out your question and those who want to understand how you got to your question so they can reform it if necessary. Before I lose group A let me blurt it out: I need a relay that will stay...

diysolarforum.com

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Ha! Totally watched that yesterday. Thank you. I think the all in one inverter I'm considering buying (listed models in above post) do have an ATS built in.

newbostonconst said:

and legally back feed the grid after getting the power companies approval.

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Or alternately if you want to start small you could use a GT inverter configured for non export. That way you only need a building permit. Enphase microinverters can also be configure for non export with the right equioment.

I think I'm in a little over my head here. Getting the utlity inolved is probably not what I want right now just because it's new ot me and I'm starting this as a hobby. I may just use the battery directly to charge stuff int he garage until I learn more!

Great idea, start small and learn as you go. Learn how to do things the safe way and not get hurt.

DouglasHHI said:

Take a look at the Reliance transfer switch, they are used for powering circuits from a gas generator but can be used with solar. It gives you the separation from the grid and control as to what circuits you want to power with solar. You just plug the inverter into the transfer switch and flip the switches from grid(line) to solar (gen). I have a 6 circuit switch wired into my main panel and can power them with my gas generator or from my solar inverter. I can pick which circuits to power depending on the load and how much power I have stored in my batteries.

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Second this. The reliance pro-tran series are VERY easy to wire to circuits in your panel. They have some YouTube videos demonstrating how. You could buy a 6 circuit version and have all 6 circuits powered by solar, grid or a combination. You decide based on switch position

Mac6792 said:

Second this. The reliance pro-tran series are VERY easy to wire to circuits in your panel. They have some YouTube videos demonstrating how. You could buy a 6 circuit version and have all 6 circuits powered by solar, grid or a combination. You decide based on switch position

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Thanks! I'll check out videos online. And this is manual, correct? I'm wondering if power would be uninterrupted when switched?

Jlomb436 said:

Thanks! I'll check out videos online. And this is manual, correct? I'm wondering if power would be uninterrupted when switched?

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Manually switched. Power is not interrupted (if you're quick)

Mac6792 said:

Second this. The reliance pro-tran series are VERY easy to wire to circuits in your panel. They have some YouTube videos demonstrating how. You could buy a 6 circuit version and have all 6 circuits powered by solar, grid or a combination. You decide based on switch position

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So in short, I could have my inverter to a sub-panel by the actual inverter so I can than place an outlet or two nearby. Then, I need to run some appropriately gauged wire (dependent on inverter watt capability) to the Reliance switch (which I can manually turn off or on as needed, just like you would with a generator). Between that, I should have an appropriately sized kill (knife?) switch. I'm assuming I need to wire the circuits I want directly to that Reliance switch (obviously outside my normal panel). I think that all make ssense if I got tha correct. It's manual, which isn't the best but not a deal breaker. I'd still be back-feeding the grid though, right? Or no?

Jlomb436 said:

So in short, I could have my inverter to a sub-panel by the actual inverter so I can than place an outlet or two nearby. Then, I need to run some appropriately gauged wire (dependent on inverter watt capability) to the Reliance switch (which I can manually turn off or on as needed, just like you would with a generator). Between that, I should have an appropriately sized kill (knife?) switch. I'm assuming I need to wire the circuits I want directly to that Reliance switch (obviously outside my normal panel). I think that all make ssense if I got tha correct. It's manual, which isn't the best but not a deal breaker. I'd still be back-feeding the grid though, right? Or no?

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Think about the reliance switch as if you're interrupting the load circuit. These circuits from your main panel in essence run through the transfer switch and back to the main panel. What the transfer switch does is gives you the option to continue powering them with the grid, power them via solar (or a generator) or turning them off. You will run an appropriately sized ac output from the inverter to the switch and should have some sort of ocpd to protect that wire. I'd placed it by the inverter. No you're not back feeding the grid this way. You're instead sourcing power from a different place for select load circuits

If you don't want to deal with selling back to the grid, you need to get an off-grid inverter/charger. Connect the AC In to the main breaker box. That can use the grid, when available, to help charge the batteries if needed/wanted (depending on how you configure it). Connect the inverter AC Out to a subpanel that supplies power to outlets you want backed up. You CANNOT connect AC Out to the main panel, that would backfeed to the grid and be bad. Normal operation will be the solar charge controller will charge your batteries, and again, depending on how you configure the inverter/charger, the grid can help keep the batteries topped off if needed. The inverter will power your critical needs. When the grid goes out, any outlets not supplied by the critical loads panel will go out. You will never backfeed to the main panel and the grid.

The downside to this configuration is that if you provide all of the power to your critical loads during the day, and your batteries are topped off, so you don't need any more power but the sun is still up, then the solar charge controller will turn off the panels, throwing away potentially free energy. So plan the system well to match your loads to your solar array.