What do I need for a Pre wire for solar backup system?

[Jchance]

I’m planning on having a small, 800 sqf, Amish Cabin built within the next 2 years. I want to eventually build a solar backup system myself, that will run the entire cabin. I’ve built a small solar system in my RV, so I have some basic knowledge, but for the next 1-2 years I will be coming back here for more!

Having said the above, when I order the cabin to be built, what would be the best thing to have the builder install to my 200 amp load center to accommodate my future solar system? I know I could ask for a transfer switch, but is there anything else I should have them install? Also, I would like specific make models of a transfer switch or any other device, if anyone has experience with them? My space will be very limited for the entire system, it might have to share a small utility closet, so size will matter!

thanks in advance!

 

[Hedges]

I like main disconnect only, no branch breakers. Using Polaris lugs that can feed one or more sub-panels (assign one to critical loads, another to less important.)
This makes it easy to insert an inverter for backup.
Each sub-panel should have interlocked "generator" breaker so you can select grid or inverter.

Transfer switches are expensive. Interlocks are about $50, and branch breaker about $50 depending on amperage.
I use Square-D QO, which has copper busbars for 125A and larger panels. Homeline is aluminum, and interchangeable with a few other brands. There are some other brands with copper.

You can get "solar ready" panels with separate breaker, but be prepared to pay $thousands.


To save space, check out Midnight's offerings. They use Square D breakers in some boxes, and have interlocks for inverter bypass.

 

[Jchance]

I like main disconnect only, no branch breakers. Using Polaris lugs that can feed one or more sub-panels (assign one to critical loads, another to less important.)
This makes it easy to insert an inverter for backup.
Each sub-panel should have interlocked "generator" breaker so you can select grid or inverter.

Transfer switches are expensive. Interlocks are about $50, and branch breaker about $50 depending on amperage.
I use Square-D QO, which has copper busbars for 125A and larger panels. Homeline is aluminum, and interchangeable with a few other brands. There are some other brands with copper.

You can get "solar ready" panels with separate breaker, but be prepared to pay $thousands.


To save space, check out Midnight's offerings. They use Square D breakers in some boxes, and have interlocks for inverter bypass.

Awesome thanks, do you have links or specific model numbers you can post here to any of these items?

 

[Jchance]

Also what about an ATS? Any advice or recommendations on those? Would be nice to have it auto switch between grid and solar autonomously.

 

[Danke]

Are you going to mount any on roof? If so, that would be a consideration in construction - trusses/spacing, etc.

 

[Jchance]

Are you going to mount any on roof? If so, that would be a consideration in construction - trusses/spacing, etc.

No Danke, It’s a small cabin, I’m thinking of putting the panels behind the house, off to the back right. I don’t want to ruin the look of the metal roof.

 

[Jchance]

Also what about an ATS? Any advice or recommendations on those? Would be nice to have it auto switch between grid and solar autonomously.

I found this ATS. https://a.co/d/7EWDSRt
Yes it’s pricey but I think it’s worth it. We will rent out the cabin when we’re not using it, (Air B&B), so I thought it would be a good idea to have an ATS. The biggest loads will be a W&D, HW heater, 2 mini split heat pumps and a well pump, so I’d like to power up the entire panel. Of course we will have other appliances, but those are the major ones.

 

[Nobodybusiness]

I use Square-D QO,

I like the Square D QO panel.
Makes it easier for AFCI breakers. No pigtails.

 

[Jchance]

I like the Square D QO panel.
Makes it easier for AFCI breakers. No pigtails.

This panel your recommending, it would have to be manually turned on? I’d really like to have an ATS. I need to learn more about the integration of solar into a panel!

 

[Hedges]

I like the Square D QO panel.
Makes it easier for AFCI breakers. No pigtails.

"Plug on Neutral"
(Check the recall, somebody didn't torque a screw.)

I happen to have one, the rest of my dozen panels (some installed, some waiting) don't. No plug-on neutral breakers yet.

This panel your recommending, it would have to be manually turned on? I’d really like to have an ATS. I need to learn more about the integration of solar into a panel!

I'm just talking about breakers in a panel, not an ATS. They can have an interlocked breaker for manual transfer.

Then there area panels like Reliance with SPDT and DPDT to select individual circuits for generator or inverter.

Then there are manual transfer switches for the whole house or whole sub-panel.

Then there are automatic transfer switches. Usually to transfer house to generator if grid goes down.

When you get a hybrid, or a battery inverter that AC couples to GT PV inverters, most act as an automatic transfer switch or rather a UPS. If the grid goes down, downstream loads are picked up by the inverter. Catch is, inverter and batteries can't power everything the grid could. So maybe you only want "critical loads" or "important loads" automatically backed up.

This is one place where manual transfer switch or interlock comes in. Communications can stay up automatically. Other loads, you can manually enable. But if battery goes low, need to disable those less important loads.

My inverter, Sunny Island, can command relays to shed loads at two different battery states of charge. So could run A/C only when battery full, for instance, refrigerator down to a lower state of charge, communications until its dying breath.

There are 3rd party monitors and controls as well.

You need to decide what you want to power, how much battery is needed, plan a mechanism to shed what can't keep running. For now, my shedding is manual. If I don't, everything shuts off until battery recharges sufficiently, then comes back on.

 

[zanydroid]

Manual interlock with breakers is likely limited to 100A or 125A with regular North American breakers.

If European style DIN MCBs are available in larger size than that, with interlock able handles, then that is a way to scale above that.

You might also be able to parallel if the individual lines are big enough under NEC. And then gang together a big row of 4, 6, or 8 breaker poles.

 

[zanydroid]

my 200 amp load center

I’m planning on having a small, 800 sqf, Amish Cabin built within the next 2 years.

These are contradictory. I sort of get maybe pulling 200A just because POCO charges the same. But I find it hard to believe you can use this much.

IOW, maybe if you run a load calculation maybe you would find that 100A is enough and save some coin on the equipment. It can be a few hundred dollar delta in some individual pieces of gear.

A 200A critical loads panel will require a monster system to feed when grid is down

 

[Hedges]

Awesome thanks, do you have links or specific model numbers you can post here to any of these items?

Here's what I got and just mounted, with separate meter socket above it:

Square D QO 200 Amp 2-Pole Outdoor Circuit Breaker Enclosure with QOM2200VH Breaker QOM2E2200NRB - The Home Depot

The Square D by Schneider Electric QO 200 Amp Outdoor Circuit Breaker Enclosure includes a two-pole QOM2 frame sizes circuit breakers 100-225 amp capacity for use as an exterior disconnect. This breaker

www.homedepot.com

It has large lugs for L1, L2, N, and 4 smaller lugs for N & G (assuming bonding screw used here, first disconnect.)
Looks like I can fit two Polaris 4-port 250MCM to 6 awg connectors side by side, for multiple L1 & L2 taps. Wires can feed through, so I'll connect two 100A boxes using a single setscrew.
I'm going to try to get clever and thread N and G wires through the lugs on panel as well.

https://us.rs-online.com/product/polaris/ipld250-4/72120846

Manual interlock with breakers is likely limited to 100A or 125A with regular North American breakers.

Homeline has a 4-gang breaker for 200A that looks like it would interlock.
QO, the 4-pole 200A breaker has handle in the middle, so wouldn't interlock without modification of the UL listed piece of sheetmetal.

But as you say, 200A is more than we expect a cabin to need. 125A should be sufficient. And it takes quite a PV/inverter system to supply that much.

 

[Hedges]

I found this ATS. https://a.co/d/7EWDSRt
Yes it’s pricey but I think it’s worth it. We will rent out the cabin when we’re not using it, (Air B&B), so I thought it would be a good idea to have an ATS. The biggest loads will be a W&D, HW heater, 2 mini split heat pumps and a well pump, so I’d like to power up the entire panel. Of course we will have other appliances, but those are the major ones.

Start looking at inverters. Most act as a UPS, so automatic transfer switch not needed.
A manual bypass is useful if inverter fails and needs to be worked on.

 

[zanydroid]

The cost of two 200A breakers is not going to be cheap unless you go hunting on eBay. Also need to make sure if they make the correct shape interlock for 4 space breakers, if it’s from a third party UL listed plate, it could be a ridiculous cost for a small piece of steel.

Anyway I agree that hybrid is a more efficient starting point for the design. Avoiding putting branch breakers in a combo meter-main is objectively a no-brainer for saving time later.

 

[Jchance]

When I said 200 amp panel, that’s what’s included in the build of the cabin. It’s an 8000 Sqf cabin, I will never need or use that much.

For now, I just need to ask the builder if they can install any necessary devices to facilitate a future system. I’m not very familiar with what might be needed in a home system, other than a transfer switch, so I’m still leaning. In my RV I installed 4 panels, a charge controller, a PV breaker and necessary wires, fuses etc.. I don’t have an inverter, but I also carry a SoGen as a backup. I just plug the RV into it.

So a lot of what everyone is suggesting is new to me, but I’m comfortable working with electric and electronics. I’ve done quite a few electrical projects in the past, sub panels, wired mini splits, 240V electric baseboard, lighting, dedicated outlets for RV’s and homes etc… this project will take me at least 1-2 years, I want to take it slow and not make any mistakes. I’m think of a $10-$12k budget for products and doing it myself, however, I might higher someone, but I’m picky, I don’t like sloppy work and installing the system myself means I’ll know all it’s components and it’s operation in-depth. There’s also a possibility I might just go simple with a couple of expanded EcoFlows or similar, I just feel that a built system will be much better, I just need to keep learning.

 

[Hedges]

You need to figure out maximum wattage of loads, starting surge, kWh per night.
Well pump could be the highest surge, unless it is something like Grundfos with VFD.

Many systems use deep well pump to pressurize water to house. Using it to lift water into tanks, only small pressure pump would be needed at night.

Mini-split heat pumps could be much lower current, but a lot of kWh. Operating at night means lots of battery. If they have VFD, soft start. But non-PF corrected VFD as common for the US upsets some inverters like mine (which are AC coupled with separate GT PV inverters). If not AC coupled, maybe not a problem.

You say "backup system", so normally on-grid but sometimes has to run with grid down.
A/C loads aren't difficult if only needed when the sun shines, because can be powered PV direct.
A/C at night or heating is difficult. Less sun during the day in winter, and batteries for night get expensive to be that large. Batteries only used for backup during power failures (say 1% of nights?) would cost you $10.00/kWh of use.
Consider propane etc. if backup heating required.

 

[MAC20121]

I’m planning on having a small, 800 sqf, Amish Cabin built within the next 2 years. I want to eventually build a solar backup system myself, that will run the entire cabin. I’ve built a small solar system in my RV, so I have some basic knowledge, but for the next 1-2 years I will be coming back here for more!

Having said the above, when I order the cabin to be built, what would be the best thing to have the builder install to my 200 amp load center to accommodate my future solar system? I know I could ask for a transfer switch, but is there anything else I should have them install? Also, I would like specific make models of a transfer switch or any other device, if anyone has experience with them? My space will be very limited for the entire system, it might have to share a small utility closet, so size will matter!

thanks in advance!

If I have a choice, I will start with a smart control breaker panel.
Some options there.

SPAN® Panel | Lower your energy bill

SPAN Panel is a re-invention of the 100 yr old home electrical panel

www.span.io

Load Centers | Smart Circuit Breaker Box | Leviton

Leviton Load Centers (i.e., Breaker Box, Circuit Breaker, Breaker Panel, Smart Electrical Panel) control your home's electrical system. Smart Circuit Breakers are now available.

www.leviton.com

Currently I have installed emporia add-on to understand my load/demand.
for solar find the appropriate appliances that support solar. check out solar hybrid AC/Heat Pump option.
Also, small wind turbine(s) if wind condition good. Wind is energy, not to be counted as capacity.

 

[hwy17]

I didn't read the whole thread but my advice would be wire up all your loads on a subpanel.

Have a main panel with a main breaker and then just one breaker on it that goes to the subpanel where all the loads are wired to.

This way, you can easily intercept that feeder and turn your subpanel into a CLP.

Preferable if the main panel has extra spaces in it, and the wiring allows good access for the interception or parallel feeder.

I'm assuming here you will have grid power first. If this is off grid completely nevermind.