Midnite Solar Announced their new 10kw AIO at Intersolar Today
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For using the 200 amp pass through for the entire house, that's all fine if the grid remains up. The inverter produces up to 10 KW, the grid makes up the deficit. If the house needs less than 10 KW, you can export to the grid the excess you can make.
If the grid fails, then the entire house could be well above 10 KW and the inverter will then overload and fault out. If that doesn't happen right at the moment of grid failure, it could happen later when heavy loads randomly stack together.
The only treatment is to manually go flip off breakers when the grid fails, then go flip them back on when it comes back. If you are lucky, you can do this before the inverter overloads. If you aren't, you are doing this in the dark and restarting it.
A backup panel does this for you automatically. A backup panel doesn't require a 200 amp pass through, only what the backup panel loads will be.
The other aspect is that putting the inverter in the utility feed to the main breaker is more complex wiring wise. You have to shut off service at the meter to do that and work with heavy cables. A backup panel operates on a load breaker from the main panel which makes it much easier to install due to lighter wires and not having to touch the utility feed.
I'd rather rewire a few branch circuits than deal with rewiring the 200 amp utility feed. Then the system automatically load sheds when the grid goes down. You can, of course, wire the 200 amp pass through capable inverter in this way, but the 200 amps is now way overkill.
Mike C.
Hedges
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More like 3 or 4 12kW inverters to pick up the load of 200A 240V = 48kW?
Schneider uses external 200A relay rather than paralleling relays inside multiple inverters.
Sunny Island parallels 2 56A relays of 4 120V inverters for split-phase, but I had to select circuit breaker brands that didn't differ significantly in resistance and cause current imbalance (which Square-D QO did).
As several of us mentioned, loads on 200A service likely exceed inverter output, so need a manual or automatic load-shedding arrangement. A priority switch would be one approach, and could be used on-grid as well.
realpinochet
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Good points but my important stuff like computers etc are on backup so for me it would not be a big deal..then I could just tun off the AC, dryer and whatever else I have going until the grid comes back on. Assuming the inverter would just shutdown and it would not hurt it ..it wouldn't be a big deal for me unless I'm missing something. But yes, I can see how having a sub panel can be beneficial. I'd have to go read the specs again but doesn't this inverter have smart load circuits for 120/240V. If so, can you just wire a sub that feeds the big items and if the grid fails the inverter just powers down that circuit to shed the heavy loads?
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Hedges
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Not sure inverters have smart load shed for more watts/amps than inverter can put out. When presented with that they may grunt for 60 milliseconds (enough to fast trip a breaker rated for < 1/5 of surge capability) then shut off.
What I have seen load-shed signals for is derating (over-temp, time to reduce load) and SoC.
I think loads in excess of inverter continuous rating should be on a separate panel. You can then manually turn some off before powering that panel from inverter. This can be done as interlocked backfeeding of main panel, although that can mean inverter doesn't see grid return and can't pick it up automatically.
What I have seen load-shed signals for is derating (over-temp, time to reduce load) and SoC.
I think loads in excess of inverter continuous rating should be on a separate panel. You can then manually turn some off before powering that panel from inverter. This can be done as interlocked backfeeding of main panel, although that can mean inverter doesn't see grid return and can't pick it up automatically.
realpinochet
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Makes sense. There's a dude on youtube that has a business installing solar and he generally always uses solark and I think he stated he liked the 15k due to the 200A relays and didn't have to put in sub panels like he used to which made it a simple install. Just connect the solark/s to they main feed and then the solark/s to the panel. engineer 777 or something like that.
When you guys move items from a main panel what's the recommended way to extend the wires..wago connectors? I'd rather move the 240V loads minus well pump to a sub panel.
Engineer 775. I've watched many of his videos.
Dave911
Solar Enthusiast
Moving 240v loads to a sub panel could be difficult. Those are typically 10 gauge on up.
It really depends upon how your wires were routed into the existing main panel. Stick a tape rectangle on the wall go one by one and figure out if you can shorten the leads or if you need to extend them. Any connection device thats legal can work. But can you fit splices in the main box? You can put masking tape notes on each cable.
Hedges
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Depends on existing wiring, as Dave said. Might be able to pull out and relocate.
I would use wire nuts or set-screw connectors if extensions required.
My place I'm upgrading, existing 100A panel was on outside corner. Conduit elbow through wall to wiring box in crawl space. BX was clamped to box and had wires run through conduit to breakers, with a good size service loop. (one had wire nuts to extension wires.) I think that was 55+ years old.
My added 100A panel was further from the corner. I was able to pull out the wires, relocate BX to my new wiring box, shove wires through conduit to new panel.
I've now removed old panel, installed new 200A one, run conduit to feed it from grid and connect to 100A panel. I will eventually have a load-shed relay for backup of large loads on 200A panel, another relay for less large loads in 100A panel, and critical loads together with AC coupled PV in yet another.
How to manage whole house loads depends largely on who will be living in the house. For my wife and I, it would be simple to just not turn on the larger loads until power comes back on. (And they are all off normally; we turn them on manually.) For a homeowner who never thinks about power, then the critical loads panel makes more sense.
If the power fails with the large loads active, the whole house will go down when the inverter faults out for overload. You can't know when the grid will fail in advance, so this could happen any time.
The only treatment to this is never run the house at loads larger than the inverter can handle. For example, only operating one of the following at any given time: HVAC, range, dryer, water heater This takes a lot of human management to coordinate and plan. If you are successful at doing that, congratulations, you didn't need 200 amp service to being with.
If you want your backup power to not fail, the the backup panel makes sense even for people who think about power. I don't see a backup panel being the right choice because people are somehow uninformed.
Mike C.
Quattrohead
Solar Wizard
I have an all electric home in Florida and I have struggled to overload test the EG4 18k. You have to be super determined to have the stove, dryer, water heater and HVAC running at the same time 
Brucey
Solar Wizard
I have propane for my large loads but can't a stove with a bunch of "burners" on and the oven take nearly 12kW by itself?I have an all electric home in Florida and I have struggled to overload test the EG4 18k. You have to be super determined to have the stove, dryer, water heater and HVAC running at the same time
timselectric
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You can't overload imaginary equipment. lolI have an all electric home in Florida and I have struggled to overload test the EG4 18k. You have to be super determined to have the stove, dryer, water heater and HVAC running at the same time
I put my sub panel close to the main and there was enough slack to move any circuit over without extending wires. That’s something I wanted to avoid.
As we plan out the new house and barn, I'm struggling at finding ways to go beyond about 10KW at any given time, unless my wife suddenly decides to prepare a meal akin to Thanksgiving dinner. I'm pretty sure she'd give me a heads up for that.
At our present property we have a 3-BR guest house and a 3-bay garage with a 1200 SF apartment above it. Mini-splits in both buildings (house has 3 indoor units, apartment has 2). No solar in either of these buildings (my solar system powers three outbuildings). When the power goes out, a 12KW Kohler generator kicks on. That generator powers both those "main" buildings without sweating, even if we turn on the conventional electric dryer that pulls a solid 5-6 KW and are doing laundry, which activates the conventional well pump periodically.
Now, granted... The stove is currently propane, and the new house will be an induction cooktop. Water heating is a Rinnai tankless in both buildings now, and we're going with an electric HP type in the new house. But we're also switching to a Grundfos SQ well pump and a HP dryer. So... as I see it, if we use modern equipment (heat pumps) and a better well pump, and just avoid having everything on at once, it seems pretty hard to justify more than about 12KW of inverter. Feel free to debate, but it seems much of this just comes down to a willingness to manage loads just a little bit.
At our present property we have a 3-BR guest house and a 3-bay garage with a 1200 SF apartment above it. Mini-splits in both buildings (house has 3 indoor units, apartment has 2). No solar in either of these buildings (my solar system powers three outbuildings). When the power goes out, a 12KW Kohler generator kicks on. That generator powers both those "main" buildings without sweating, even if we turn on the conventional electric dryer that pulls a solid 5-6 KW and are doing laundry, which activates the conventional well pump periodically.
Now, granted... The stove is currently propane, and the new house will be an induction cooktop. Water heating is a Rinnai tankless in both buildings now, and we're going with an electric HP type in the new house. But we're also switching to a Grundfos SQ well pump and a HP dryer. So... as I see it, if we use modern equipment (heat pumps) and a better well pump, and just avoid having everything on at once, it seems pretty hard to justify more than about 12KW of inverter. Feel free to debate, but it seems much of this just comes down to a willingness to manage loads just a little bit.
Electric stove and electric water heater together will likely nearly max out 12kW of inverter. That's without anything else running. Heat pump dryer and washer, plus will pump will soon add around 2kW yet. Grundfos well pump alone will be between 600-1500w depending on which specific model you end up with.
I'm off grid with gas water heater and stove, but grundfos well pump, electric dryer and washer in a ~1700 sq ft "shop house" and I have seen loads hit 8 kW.
It's easy to go above 10kw daily in my all electric house.
Just doing laundry achieves that. Water heater 4.5kw, well pump 1.8kw, clothes dryer 6kw.
Heck just the dryer and water heater together are over 10kw
.
In the summer around dinner time it's nothing to see 18-20kw demand
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A few things to keep in mind when looking at the whole 200A vs 100A passthrough subject:
- The goal is usually to have a flicker free transfer to inverter when grid goes down. If this happens you won't find out grid is down, and therefore you won't manually manage peak loads!
- For a DIY install where you keep a close eye on things 200A may be fine. For a professional install fot a customer who just wants seemless back power 200A will likely NOT work. It's really not cut-and-dried for every install.
- Often it's not as simple as "just running the 200A service through the inverter." Often that actually consists of getting a disconnect scheduled with the power company, adding an outdoor knife disconnect, sometimes it means you need to do a line side tap, and if you want a bypass/backup option in case of inverter failure you will also be looking at 200A equipment if you go with a throw style transfer switch for bypass. (Although you can go with a main to bus interlock.)
- In my experience is actually often easier to transfer critical loads to a new panel, than it is to revise the whole service!
- At the end of the day it still comes down to you looking at what is the right setup for your specific needs.
Thinking out loud in regards to a whole 200a feed ... if you were computer savvy and already had something like Home Assistant running, couldn't it be programmed to flag a grid down situation? Could there be a simpler way to indicate the grid were down so one could reduce loads? This would not help if you were already over the threshold when the grid went down, but it could give a heads up.
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