455dan
Solar Addict
Yep, I agree or I wouldn't have kicked the 200 amp breaker off 3 times over the years, outbuildings and a garage /shop add up especially when choosing to use forced air electric heat in the house.
Feeding whole house 200 amp panel off-grid
- Thread starter GA_Solar
- Start date
Ok, I hope you have a quiet generator because it is going to get some runtime. Also stock up on fuel because a big generator will consume lots. I'm not trying to be a smart a$$ just being real.
zanydroid
Solar Wizard
Going off grid as your first large system (I don’t know if you have incremental milestones set) seems like too big of a jump and I get an overly optimistic vibe here.
The best build threads I like here combine load planning, generation modeling, with a plan to do 1-2 years on the first large set of inverters and batteries. You can get rid of some of those and still be ok with an iterative plan.
The best build threads I like here combine load planning, generation modeling, with a plan to do 1-2 years on the first large set of inverters and batteries. You can get rid of some of those and still be ok with an iterative plan.
Warpspeed
Solar Wizard
And I am wondering how its possible to mount 32 fairly large solar panels on "a small mobile home".
GA_Solar
New Member
Who said anything about panel mounts?
chrisski
Solar Boondocker
What are you doing to the panels, ground mounts? Lean them on a wall? Put them on grass?
GA_Solar
New Member
Most of my home has been on solar for 9 years, jumping to a larger system for; full-home off-grid is the next step for me. Not a big jump at all.
GA_Solar
New Member
Building ground mounts, next to my current ground mounts
Ahh.
This is making a LOT more sense as the details are disclosed.
Cool, tell us about your place, the hvac, the roof design, the building shading and awnings, lets work on a great setup!
GA_Solar
New Member
Shopping on Current Connections now. Might just design a system from them. I've had a midnight classic cc for a long time, great product.
~The whole point of my post was how to feed a 200a panel.
HVAC is a low power mini-split 30a, roof don't matter, no shade, big field. Command center in my tool shed. Awesome forum here, thank you! I'm waiting on funds to start this proj. within 90 days likely.
~The whole point of my post was how to feed a 200a panel.
HVAC is a low power mini-split 30a, roof don't matter, no shade, big field. Command center in my tool shed. Awesome forum here, thank you! I'm waiting on funds to start this proj. within 90 days likely.
SolarTexan
New Member
Take the output from your inverter(s) and connect directly to the 200a panel where the currently incoming grid power is connected. (make sure grid power is removed before doing this)
Do you know what your max kW usage will be? Mine has been up to 19kW briefly just a few times. I have propane heat, oven, and cooktop, and electric hot water heater, two 3 ton central a/c units, and well pump. You need to know your max watts usage so that you don't have nuisance overloads of your inverters if they are too small.
I think you will need more battery storage than 25.6kWh, or you will end up with having to run a generator frequently.
Do you know what your max kW usage will be? Mine has been up to 19kW briefly just a few times. I have propane heat, oven, and cooktop, and electric hot water heater, two 3 ton central a/c units, and well pump. You need to know your max watts usage so that you don't have nuisance overloads of your inverters if they are too small.
I think you will need more battery storage than 25.6kWh, or you will end up with having to run a generator frequently.
patrickparrott
Solar Enthusiast
My backup is going to be my already installed generator. The utility can be very undependable. That's the reason for the generator in the first place.
We just built a new barn with living quarters, totally off grid. It is all electric except for propane to supply heat to the first floor slab if needed during the coldest months. Everything else is electric (3 mini-split heat pumps, full size electric induction range with convection oven, heat pump water heater, full size washer/dryer (heat pump type), well pump, etc. We aren't sacrificing anything in terms of convenience. We have the largest 200 amp panel I could find, PLUS a 100-amp sub-panel, because we wanted to separate out our circuits. But the whole thing is powered by "just" three 6000XP inverters that can each output a maximum of 25 amps (75 amps total), and we never, ever, come close to needing even that much power. We also don't even use the built-in 200 amp breaker. It just sits there unused, in case someone ever decides they need to bring in utility power to the building. We combine the three 6000XPs in a separate box using three 40-amp breakers, then run into the main panel using a 100-amp breaker (basically the same as one would do with a sub-panel). The neutral-ground bond is made in that main panel. Everything works perfectly. We never come close to our maximum power production.
American homebuilders started installing 200 amp services back when electricity was still cheap and appliances were inefficient. People were installing large HVAC systems and dryers that used resistive heat and other energy hogs that, as you noted in a post, quickly add up. But today, with just a modest amount of focus on using energy efficient appliances, there's just no need for a 200 amp panel in most homes other than the fact that you are forced to buy one to have a large number of spaces for circuits, unless you are determined to waste energy OR intend to rapidly charge multiple electric vehicles.
As others note, you generally don't need to use the 200 amp breaker built into the panel, if you're off grid. It's just there as a useless thing you were forced to buy to get the number of circuit spaces you want, in a readily-available panel.
American homebuilders started installing 200 amp services back when electricity was still cheap and appliances were inefficient. People were installing large HVAC systems and dryers that used resistive heat and other energy hogs that, as you noted in a post, quickly add up. But today, with just a modest amount of focus on using energy efficient appliances, there's just no need for a 200 amp panel in most homes other than the fact that you are forced to buy one to have a large number of spaces for circuits, unless you are determined to waste energy OR intend to rapidly charge multiple electric vehicles.
As others note, you generally don't need to use the 200 amp breaker built into the panel, if you're off grid. It's just there as a useless thing you were forced to buy to get the number of circuit spaces you want, in a readily-available panel.
NC_hydro
Solar Wizard
If you’ve already got a classic from MNS you should go with the Powerflo16 batteries and a MNS all in one. Or two if need be 
Prefersdirt
Solar Enthusiast
- Joined
- Sep 28, 2019
- Messages
- 411
Yes. I have that.
GA_Solar
New Member
Thank you, Thank you.
atlsolar
New Member
How would you do this if you still wanting grid backup/overflow? I have 2x 200a panels, one is mostly lights/outlets, but the other has 4 central HVAC units, 2 clothes dryers, 3 fridges, EV charger, etc... So I need to maintain close to that 200a service.
2x parallel 12000xp inverters --> combiner box/panel, but then how to push that into the main 200a panel WITH keeping grid power as well and preventing any backfeed issues?
For the second panel, the lights/outlets panel, I am planning on just bringing a 50a breaker from the combiner box and utilizing a manual interlock kit that I can flip in case of an outage but just leave that panel on grid only during up-time.
Zwy
Emperor Of Solar
This is how I an wiring my shop, it currently has a 200A breaker panel inside the shop which is fed from a service panel at the utility meter 250 feet away. The current 200A breaker panel gets a generator interlock and 100A backfed breaker from the inverters. At the pair of inverters is a breaker panel back fed from each inverter. This is a combiner box, the inverter terminals can only accept 6AWG wire. One could use a Polaris or junction block to combine power from each inverter. The breaker panel allows not only for circuit protection but the ability to switch off one inverter and isolate it and work on the other inverter. 4AWG wire from the backfed inverter breaker panel to the 100A backfed breaker in the 200A panel.
The current 200A breaker will become a sub panel/crucial loads panel. I will be installing a 200A NEMA 4 breaker panel on the outside of the wall and this breaker panel has feed thru lugs on the busbars. The feed thru lugs will be wired to the 200A breaker in the 200A panel inside the shop. One 100A breaker will be installed in the outside panel and that will be wired to the inverter AC input terminals. Most of the time that breaker will be off. I might install a simple knife switch inside the shop in order to switch on/off AC input and not have to go outside.
atlsolar
New Member
@Zwy - Here's my current diagram that I'm playing with for this. Similar to what you just described. Let me know your thoughts or if I'm missing anything here. Also, any notes on wiring needs at various spots in my diagram since it's a little different from yours?
I'm considering a 600a bus bar inside this combiner box, after the inverters, with loads continuing each to the 125a and 70a respective breakers. Thoughts on having both backfeed breakers be 125a? The 70a would be OFF 99% of the time, and I'd only flip grid off and 70a on in the event of a power outage where I can first manage the load on panel 1 which would be the inverse, 125a breaker ON 99% of the time. I don't think I need a breaker within the post-inverter combiner box for each since I'd probably just switch to grid in the event I needed to mess with one of the inverters.
https://a.co/d/0ctSjmO - bus bar x 2
I think I have sort of switched your ideas on the combiner/breaker box and moved mine in front of the inverters. I think there is likely a better or cheaper way to do this than just stack 3x 100a breakers, but I wanted the breaker here from the grid power and didn't know of an easy way to insert the 100a breaker into a distribution block or bus bar that wouldn't be messy. It's possible this is extremely simple, I just couldn't find the parts that made sense in my head.
I still need to map out the batteries, but I think that part should be much easier.
I may throw this same question/diagram in a new post somewhere as well.
Thanks.
I'm considering a 600a bus bar inside this combiner box, after the inverters, with loads continuing each to the 125a and 70a respective breakers. Thoughts on having both backfeed breakers be 125a? The 70a would be OFF 99% of the time, and I'd only flip grid off and 70a on in the event of a power outage where I can first manage the load on panel 1 which would be the inverse, 125a breaker ON 99% of the time. I don't think I need a breaker within the post-inverter combiner box for each since I'd probably just switch to grid in the event I needed to mess with one of the inverters.
https://a.co/d/0ctSjmO - bus bar x 2
I think I have sort of switched your ideas on the combiner/breaker box and moved mine in front of the inverters. I think there is likely a better or cheaper way to do this than just stack 3x 100a breakers, but I wanted the breaker here from the grid power and didn't know of an easy way to insert the 100a breaker into a distribution block or bus bar that wouldn't be messy. It's possible this is extremely simple, I just couldn't find the parts that made sense in my head.
I still need to map out the batteries, but I think that part should be much easier.
I may throw this same question/diagram in a new post somewhere as well.
Thanks.
Zwy
Emperor Of Solar
Those busbars are rated for 48V DC, not 120/240V AC.
Use a Polaris connector if you want to combine AC power. Having said that, there isn't any circuit protection, this is why a breaker panel is used with back fed breakers. Either way works but the extra breaker panel allows for circuit protection, plus protect the inverters and combines all the inverter output.
Both could be 100A,125A or even 200A. You have to size the wire appropriately with a larger breaker. The 70A could use 4AWG THHN but the 125A would need 2AWG with at least 90C rating.
One more thing is run each 240V circuit in separate conduit as more than 3 wires in a single conduit will have to be derated.
atlsolar
New Member
Maybe I'm misunderstanding, but there's a breaker on each end of this section, right? The breaker backfeeding the panel(s) and then the inverter has an internal Load breaker. Assuming these aren't directional, I'm thinking there's a breaker on each end that I can toggle if/when I ever need. Let me know if I'm wrong, and if so, would you just suggest replicating that 3x breaker combiner panel, but with 4x 125a breakers instead of the bus bar/polaric combiner idea? The bus bar was going to make it cheap and I didn't think there was a need for the breakers in the middle there, but if I end up going with the Polaris, it's probably the same cost and might as well just put in a small breaker panel with the 4x 125a breakers. Just seems like extra things to flip and keep track of that don't play a role in the overall system besides being connectors of sorts.
Ultimately, I'll probably end up sizing things up. I'll probably spend an additional $500 on breakers and wiring, but that's about 2.5% of the cost of the total system and gives me some future-proofing and mental relief. Hopefully the heavier wire isn't overly difficult to work with. I'll need to check on the max wiring sizes that fit into the various inverter ports and adjust accordingly from there.
Thanks for catching that and calling out.
Overall, some super-helpful quick hit tips you gave me. Greatly appreciate the ideas and help.
Zwy
Emperor Of Solar
With the breaker in the inverter, you don't need the combiner breaker box like I have. A Polaris connector would work fine.
My inverters do not have an output load breaker, but do have an AC input breaker.
atlsolar
New Member
@Zwy - Looking at how I set up the system, I was trying to take advantage of the 100a bypass capability of each inverter and using that 125a backfeed. If the inverter's load breaker is 100a, and I'm combining both into a polaris connector, if the panel did pull over 100a, it would flip the inverter's breaker, right?
If I'm correct, in order to take advantage of the 100a bypass each, and account for the potential to have large surges in panel 1, would it be better to build another output subpanel? If so, I'm thinking I buy another 200a lug panel, feed each breaker's output to it via 100a breakers. Then, use the lugs to feed a 175a breaker as the backfeed - I think similar idea but larger than what you were referencing. Or, I could just do a breaker panel with 175a on each end. Not sure it matters which, right?
Would this prevent the 100a inverter load breakers from flipping if I happened to draw 100a+ from the current polaris setup? Effectively, this would give me almost the full 200a bypass. I looked through the last year's hourly usage, and although not frequent, I have 35 hours where I pulled 13kwh or more over the hour and 5 hours where I pulled over 15kwh. I'm assuming if I used 15kwh, there could very well have been surges over 20-25kw. The 175a is likely still overkill, and maybe I'll end up going back to 125, but I found the below 175a breaker that seems to be roughly the same cost as any 125a I've found. So besides having a maybe 3-6 feet of more expensive wiring between this inverter output panel and the existing panel, cost isn't different, and this would surely give me wiggle room down the road.
https://www.homedepot.com/p/Siemens...0kA-Type-QPP-Circuit-Breaker-Q2175B/206632153
Or, would it be too stupid to just feed each inverter into panel 1 directly via 100a breakers, and then just replace the inverter --> panel 2 path with a backfeed breaker from panel 1 into panel 2 (off 99% of the time in both panels, and with an interlock kit on panel 2 only since panel 1's interlock is tied to the 100a feeds). So both inverters feeding panel 1 directly and individually, and panel 1 feeding panel 2 only on manual demand. This would likely save hundreds of dollars and be much simpler to execute, just might be too stupid of an idea.
Thanks.
If I'm correct, in order to take advantage of the 100a bypass each, and account for the potential to have large surges in panel 1, would it be better to build another output subpanel? If so, I'm thinking I buy another 200a lug panel, feed each breaker's output to it via 100a breakers. Then, use the lugs to feed a 175a breaker as the backfeed - I think similar idea but larger than what you were referencing. Or, I could just do a breaker panel with 175a on each end. Not sure it matters which, right?
Would this prevent the 100a inverter load breakers from flipping if I happened to draw 100a+ from the current polaris setup? Effectively, this would give me almost the full 200a bypass. I looked through the last year's hourly usage, and although not frequent, I have 35 hours where I pulled 13kwh or more over the hour and 5 hours where I pulled over 15kwh. I'm assuming if I used 15kwh, there could very well have been surges over 20-25kw. The 175a is likely still overkill, and maybe I'll end up going back to 125, but I found the below 175a breaker that seems to be roughly the same cost as any 125a I've found. So besides having a maybe 3-6 feet of more expensive wiring between this inverter output panel and the existing panel, cost isn't different, and this would surely give me wiggle room down the road.
https://www.homedepot.com/p/Siemens...0kA-Type-QPP-Circuit-Breaker-Q2175B/206632153
Or, would it be too stupid to just feed each inverter into panel 1 directly via 100a breakers, and then just replace the inverter --> panel 2 path with a backfeed breaker from panel 1 into panel 2 (off 99% of the time in both panels, and with an interlock kit on panel 2 only since panel 1's interlock is tied to the 100a feeds). So both inverters feeding panel 1 directly and individually, and panel 1 feeding panel 2 only on manual demand. This would likely save hundreds of dollars and be much simpler to execute, just might be too stupid of an idea.
Thanks.
Last edited:
Zwy
Emperor Of Solar
That diagram looks much better and is how I am wiring my shop system, minus the Panel 2. I would just backfeed into Panel 1 and Panel 2 would be fed by Panel 1 with a backfed breaker (with interlock). You should be able to install a 200A breaker in Panel 1 as the breaker panel busbar is rated for 200A. To save some money and cut down on breakers, (plus wire) the Lug Output Subpanel doesn't need a 200A breaker, it only needs the lugs for the 2/0 cable. A 200A or 175A backfed breaker in Panel 1 will protect the circuit. I would bump up the wire size from 2/0 to either 3/0 or 4/0. If wire is aluminum, then minimum is 4/0 if you use a 200A breaker.
Each backfed breaker will require a hold down kit.
Each backfed breaker will require a hold down kit.
atlsolar
New Member
Thanks. I was planning on just using the lugs not the 200a breaker, but for ease, I just copy/pasted the other panels... Sorry.
I was planning on using copper on everything so I could downsize and make things at least a tiny bit easier to work with. My thought on the 2/0 was the 175a backfeed breaker should only need 2/0, right? You still suggest 3/0 for that run? Just because more is better or you're saying that assuming I'm bumping up to 200a backfeed from 200a lug.
Another super-useful note here. Thanks.
Also, if I go with the "stupid" plan, the inverters each directly into panel 1 with 2x 100a, I have two concerns/questions:
- How should I organize the batteries here? I was planning on four Ruixu lithi2-16's, all in parallel, connected to the two inverters, similar to the picture below from ruixu. Does the fact I'm feeding each inverter in separately matter at all? Is it just how I connect the batteries on the comms side that matters? Do I need to make any adjustments at all to the DC parts if I skip the output panel? Any concerns or requirements if I add a handful of solar panels down the road?
- If I do go straight into panel 1 from each inverter and then tie 1-->2 with another backfeed, are there any safety concerns here? With the 175a breaker plan, there's the interlock between grid and 175a double pole, and I can manage each inverter in the subpanel(s). If I use 2x 100a directly, the interlock kit likely only blocks the 1st 100a breaker. Would I need to attach a clip or something to tie the two 100a breakers together, so they must be flipped in tandem? I assume the handle tie is all that makes it okay in the first place when there is a double pole breaker. In this case, I'd likely need a 4-pole tandem tie or something, I'm guessing. Then... Knowing that, I "sort of" lose the functionality to pull one inverter out of the system without also having to dismantle the tie (or maybe I still have this since the inverters have their own load breaker...). Long story short, is this an advisable method?
$200 2x 100a
$200 200a lug panel
$150 175a
$100 wire from output to panel 1
------
$650
$'s for inverters straight to panel 1
$200 2x100a
$50 wire from inverters to panel
-----
$250
So $400 cheaper - what do I lose here, both safety, flexibility, future, etc... It seems like not much is lost, but I'm not seeing this design from pretty much anyone with 2 inverters. Everyone has some sort of combiner panel on the output side. There must be a reason, right?
Again, thanks for all the help.
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