Move Panels / Re-Route Power Before Starting PV?

[Porter21]

Hi Everyone,

First post, been reading here for a few weeks and trying to learn. I'd like to do a small-scale DIY install this summer to get my feet wet. Wanted to solicit some pre-setup advice. Apologies if I give extraneous info, I'm just beginning with this. I'm in the U.S., so 120/240 AC power. The plan is a PV system charging 48V lithium batteries, grid-tied to charge the batteries (from grid or generator) when needed, but not back-feeding the grid. This is not meant to be a whole-house power replacement, but instead a gradual reduction of grid use and a way to reduce generator demand in case of extended outages.

Here's the situation: On my property there are 3 buildings with power: the house, a detached garage, and a shop building. Grid power comes on the property to the meter, and then splits off to the shop in one direction and then to the house in the other direction. At the meter a propane generator backs up everything. Both the shop and the house have their own electric panel (not in same location) each with a main breaker rated at 200amps. The garage is wired into the house main panel on a 30-amp breaker. There is no subpanel in the garage, just what looks to me to be DIY wiring of outlets for lights and 120V power. So:
garage <- house <- GRID -> shop

To my eye the shop roof is well-suited for solar; the building runs east to west and the one side of the roof is facing almost due south, with very little shading during the day. A key issue is also that the shop electric panel powers the well pump, which I definitely want to put on solar (I'll post begging for help with that later, once the clamp meter I ordered arrives and I can provide info on what it draws). Great: I can put the array on the roof and the inverter/chargers and batteries in the shop and power the well, but then what? Currently there's no way to send power from the shop to the house, so scaling larger than what's needed for the well pump and a chest freezer doesn't reduce the house consumption. For the house, there really isn't a convenient place for the inverters and batteries inside, so these would go in the garage. The breaker panel on the house is on the outside, about 35 feet the spot in the garage where I would locate the inverters/batteries.

The question I have here is: should the breaker panels be moved or the electric service from the grid meter re-routed to make things easier in the future? I'd have an electrician do this, of course. My thoughts were:

Option 1: From the grid meter, re-route the house service so that it goes to the shop first, with a panel which would allow it to be tied into the PV system before being sent to the house. This could also involve sending it from the shop to the garage for any PV system on the garage and house roofs. So: grid -> shop -> house, or grid -> shop -> garage -> house

Option 2: Leave main routing as is. Move house main breaker panel to garage, tie into garage/house PV system, and then send power back to house. Power from PV system on shop would then either just be for well pump, or PV power from shop would have to be sent to garage (~100feet) either as DC (expensive wires) or AC (loss on converting to AC and then back to DC for batteries).

Option 3: ?

Thanks for reading all of that, and appreciate any suggestions. I want to avoid building out the system only to find out in 3 years that I really should have addressed the power routing and main panel situation first.

 

[OffGridInTheCity]

There are many options here / no right answer. I'm off-grid so I feed power thru ATSs to various circuits in my house. You mention a generator backup so you might have experience with this. In this scenario, if Solar generation/distribution panels are located in the Shop, then all you need is to run wiring from Shop to House to feed ATSs at the house OR even Shop to generator as a generator alternative and use existing Generator infrastructure.

If you plan grid-tie, then distribution to the house could (again) be accomplished with new wiring between the Shop and House rather than move the Grid setup and the Shop already has grid access.

Running wire between the Shop and the House is a (perhaps) a DIY alternative for off-grid or grid-tie (or hybrid) to moving the existing Grid setup.

Are you planning Off-grid or Grid-Tie/Hybrid?

And, If you're going to hire an electrician (rather than DIY), my experience has been they will have strong opinions - perhaps ask them?

 

[Ampster]

I have a similar situation with a small shed that has one 20 Amp 120 volt circuit. It has a West facing roof that I could get five or six panels on. It is 125 feet from my main panel and two sub panels. My first task is to trench and put in a one inch conduit and pull some 6 or 8 AWG wire so I can have 240 volt subpanel there. Then I can use some existing microinverters to supplement my system. I am grid tied but operate my system in self consumption mode. The point for @Porter21 is the first step is to get the infrastructure in the ground so that you have flexibility configuring a system. The distance will factor into my plan by upgrading the wire size.

The system in my signature handles my needs fairly well but in the winter I could use some more capacity sp that is the driver for my plan.

 

[Porter21]

If you plan grid-tie, then distribution to the house could (again) be accomplished with new wiring between the Shop and House rather than move the Grid setup and the Shop already has grid access.

Running wire between the Shop and the House is a (perhaps) a DIY alternative for off-grid or grid-tie (or hybrid) to moving the existing Grid setup.

Are you planning Off-grid or Grid-Tie/Hybrid?

And, If you're going to hire an electrician (rather than DIY), my experience has been they will have strong opinions - perhaps ask them?

The setup will be tied to the grid in the sense that I want to be able to use the AC input on any inverter I buy to charge the batteries if they are low, but I will not send power back to the grid.

If I went with running a wire between the shop and house, I think I can DIY that once I know the required wire size. There are several places in the area where I could rent a trencher.

By ATS, I assume you mean Automated Transfer Switch? I know they exist, but that's about the limit of my knowledge of them. I didn't install the generator, so I didn't get any experience with one there. What do they do on your system? Read the available power from your PV system and then automatically select the circuits to send it to based on demand?

 

[OffGridInTheCity]

The setup will be tied to the grid in the sense that I want to be able to use the AC input on any inverter I buy to charge the batteries if they are low, but I will not send power back to the grid.

You are describing Off-Grid. Grid-Tie means you send power out to the grid - e.g. have the right equipment to sync with the grid sine wave and certifications from the power company to send power out.

If I went with running a wire between the shop and house, I think I can DIY that once I know the required wire size. There are several places in the area where I could rent a trencher.

US 240v/210v split-phase wire sizes are pretty standard and you can look them up. For example - 3 wire + ground 6AWG can do 240v/120v @ 50a for 200ft or less.

By ATS, I assume you mean Automated Transfer Switch?
I know they exist, but that's about the limit of my knowledge of them. I didn't install the generator, so I didn't get any experience with one there. What do they do on your system? Read the available power from your PV system and then automatically select the circuits to send it to based on demand?

Yes. What I do is feed grid to one side, the Solar based Inverter power to the generator side of the ATS. When the unit senses inverter power it switches to pass that along. When the inverter power goes off (batteries run down) it auto-switches back to grid. However, you need UPS support on sensitive circuits as the switch is not generally fast enough.

However the 'regular'/'cheaper' ATSs are limited to 240v/120@50a and that may not be enough to power for what you want at your house. So you could multiples wire runs of 240v@50a each. This is what I do - I have 4 x 240v@50a ATSs around the house.

However....
These days, you can buy all-in-one units that have build-in ATS/UPS. For example, you could do Shop-grid -> All-In-One-Unit -> distribution-house ATS as an example. If 240v@50a ATS is not enough or doing multiple ones is not good for you or your electrician says no... you can go more expensive Generac (type) 100a ATSs etc.

Also your generator has a way to feed power to things... how big is it, is it enough? You might be able to do.... Shop-Grid -> All-In-One-Solar-Unit -> Generator connection and feed the solar power into your system in place of the generator power. And of course be able to switch between Solar and Generator.

 

[Ampster]

Grid-Tie means you send power out to the grid - e.g. have the right equipment to sync with the grid sine wave and certifications from the power company to send power out.

I agree with what you said with respect to having equipment to sync with the grid. Increasingly I see more people use GT inverters with limiters or CTs to prevent export to the grid. In that case no permission is required from the power company. Perhaps there is a better descriptor but it might be an option for the OP if he is just trying to reduce his bill.
I am a big fan of the traditional GT arrangement but as NEM benefits continue to be eroded I am looking at ways to self consume power generated by my panels.

 

[OffGridInTheCity]

I agree with what you said with respect to having equipment to sync with the grid. Increasingly I see more people use GT inverters with limiters or CTs to prevent export to the grid. In that case no permission is required from the power company. Perhaps there is a better descriptor but it might be an option for the OP if he is just trying to reduce his bill.
I am a big fan of the traditional GT arrangement but as NEM benefits continue to be eroded I am looking at ways to self consume power generated by my panels.

Yes. I don't think of local grid-tie w/limiter as a 'grid tied system' as it's not legal/safe to send (excess) power out to "The Grid". Its more of local concept to reduce internal use and I'm guess the OP is looking for 'an approach' rather than a nuance at this point. But also agree - definitions of things are varied

 

[Porter21]

These days, you can buy all-in-one units that have build-in ATS/UPS. For example, you could do Shop-grid -> All-In-One-Unit -> distribution-house ATS as an example. If 240v@50a ATS is not enough or doing multiple ones is not good for you or your electrician says no... you can go more expensive Generac (type) 100a ATSs etc.

Also your generator has a way to feed power to things... how big is it, is it enough? You might be able to do.... Shop-Grid -> All-In-One-Solar-Unit -> Generator connection and feed the solar power into your system in place of the generator power. And of course be able to switch between Solar and Generator.

Thank you for the replies and the information. My generator is a 21 kwh Generac, which is more than enough to power everything I need if the grid goes down for a bit. I looked at some videos of the Generac generator ATS; if I understood it correctly, it switches all-or-nothing between grid and generator. Either the house gets 100% of its power from the grid, or 100% from the generator, with the default being grid. With a second such switch, I could feed the output of the first ATS (grid/generator) into the secondary input of the second ATS, with PV going into the primary. Then it would default to PV, and if the PV output weren't enough, it would switch to either grid or generator. This would still be all-or-nothing, though. If my needs went 100 watts over what I had available, it would go to grid, and the PV output would be lost.

It sounds like what you have set up is able to add grid to what you are getting from solar. So if you running 3 of 5 of your ATS circuits off of PV and then something on circuit 4 turns on and needs more power than you have, it can feed grid to that circuit while keeping the other 3 on PV. Is that right? If that's correct, I'd want to set my system up in a similar way, so I would get the benefit of lowering my grid usage on a day-to-day basis. I suppose that if I don't tie the PV system into the generator in some way, it wouldn't be able to tell the generator not to turn on if the grid went down but there were plenty of PV power available. In that case I would just have to switch it off manually at the generator.

 

[Porter21]

I agree with what you said with respect to having equipment to sync with the grid. Increasingly I see more people use GT inverters with limiters or CTs to prevent export to the grid. In that case no permission is required from the power company. Perhaps there is a better descriptor but it might be an option for the OP if he is just trying to reduce his bill.
I am a big fan of the traditional GT arrangement but as NEM benefits continue to be eroded I am looking at ways to self consume power generated by my panels.

I had originally thought that I would grid-tie to take advantage of net metering. My estimates, based off of power bills and the Sun Earth tools sun tracker and the PV watts calculator, made it look like a good way to zero-out my power bill in a few years of adding capacity. But after looking into the local utility's net metering conditions, the extra permitting and equipment costs, etc., it doesn't look like it makes that much sense for me.

 

[Ampster]

But after looking into the local utility's net metering conditions, the extra permitting and equipment costs, etc., it doesn't look like it makes that much sense for me.

That sounds like a good plan. I have enough differences in production and consumption that I still need Net Metering but my system has evolved to a self consumption mode. I also use my batteries to carry me through the peak rate period. My big loads are charging EVs and that has evolved to more often doing that in the daytime to use available solar. Lots of good ideas here.

 

[OffGridInTheCity]

First, let me say that my comments are for discussion only. I'm not an electrician or expert but rather I'm hoping that by sharing my limited personal experience it will help you think of good questions to ask your own experts / get a great solution for your situation

Thank you for the replies and the information. My generator is a 21 kwh Generac, which is more than enough to power everything I need if the grid goes down for a bit.

OK, cool. That's in range of 240v@100a - e.g. a 100a ATS.

I looked at some videos of the Generac generator ATS; if I understood it correctly, it switches all-or-nothing between grid and generator. Either the house gets 100% of its power from the grid, or 100% from the generator, with the default being grid. With a second such switch, I could feed the output of the first ATS (grid/generator) into the secondary input of the second ATS, with PV going into the primary. Then it would default to PV, and if the PV output weren't enough, it would switch to either grid or generator. This would still be all-or-nothing, though.

Yes. You can have a series of ATSs like this.... An ATS has 2 inputs - grid (default) and generator (relays switch to this if power is present). In the following, the grid of ATS 1 would run if Grid was present but nothing else. ATS 1 would switch to Gen side if ATS 2 sends power. You get the idea.


From your comment below it occurs to me that you could also do this - e.g. rewire your generator output to charge the battery bank for the solar system. A lot of the systems have remote-auto-generator-start options when the battery voltage is too low. Don't know if your generator has auto-start etc.

If my needs went 100 watts over what I had available, it would go to grid, and the PV output would be lost.

Well - its a matter of ATS max, how much can inverters deliver / wire size - e.g. proper circuit breakers. If you need more than 100a @ 240v then you need a larger ATS or multiple ATS.

It sounds like what you have set up is able to add grid to what you are getting from solar. So if you running 3 of 5 of your ATS circuits off of PV and then something on circuit 4 turns on and needs more power than you have, it can feed grid to that circuit while keeping the other 3 on PV. Is that right?

If I overload, then circuit breakers will pop on the inverters and things will default to the grid. One can wire things so that if everything is turned on at once, the inverters will overload BUT manage things so you don't run things all at once. However, for normal life with grid available - I don't recommend this because in normal living mode you just don't think about it much.

In my case, I've distributed the inverter output to specific circuits so this won't happen - leaving a few circuits that aren't part of the solar system. For example, the Oven is rarely used and in a dire emergency I could re-wire the main panel to overload and just not run the Oven and Dryer at the same time.

In addition, the MTS at the main panel let's me choose which circuits are grid-only and with care active on the PV system by a simple flip of the switch between "line" and "gen" - so I don't have to change wiring to enable/disable a circuit for consumption. This let's me control the overall load to a degree.

Here's kind of an overview - we can run 80% of house at a level that's perfectly comfortable.

If that's correct, I'd want to set my system up in a similar way, so I would get the benefit of lowering my grid usage on a day-to-day basis.

Yes - the ATSs are automatic. My system is setup to turn the inverters on when the batteries get to 51v and off at 49.5v. When there's enough solar, the house switches over and when the batteries run out, it goes back to grid. I don't have to do anything.

A benefit is that I can turn off the solar system to work on it and it just defaults to grid - so the house runs smoothly while I work on things .

A downside is I have UPSs on key circuits for Computers/TV. In fact, I ran set of sockets thru the house with a central UPS. Today's all-in-one's may have UPS built-in so this might not even be an issue for your.

I suppose that if I don't tie the PV system into the generator in some way, it wouldn't be able to tell the generator not to turn on if the grid went down but there were plenty of PV power available. In that case I would just have to switch it off manually at the generator.

An alternative instead of switching between generator and Solar would make Solar the 'generator' and use your generator to charge the batteries if they are too low / not enough PV.