Can someone review my back up system design?
- Thread starter joshua4pr
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It does but I want to isolate the inverter in case it fails I can still use the grid.
Ah, understood. If that happens to me I just plan on taking 10-15 min to bypass. I'm too cheap to buy an extra breaker and transfer switch!
Yeah its a typo my bad. It is lv6548. 300 amp fuse? should I use 2/0 instead of 4/0?
Planning to use 8 400 watt panels still dont know the VOC but should be around 39 v. Planning on 2 serial strings since the inverter will take 2 strings 250v each . With 25 amp breaker for disconnect. Should I add a line fuse as well in case the breaker fails? Thank you for your reply. A beginner here trying to assemble my own backup system.
John Frum
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You don't need 4/0 awg but it won't hurt.
If you use 4/0 awg you can use a 400 amp class t fuse.
John Frum
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you don't need over current protection until you get > 2 strings in parallel.
You do want a double pole single throw switch as a means of disconnect.
my thinking on the 4/0 is in case i want to upgrade later then i dont have to buy wire again.
quick question, is it ok to use a 300 amp instead of the 400 one? the Go power Tclass 400 amp is sold out everywhere
John Frum
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Sure.
EastTexCowboy
Solar Wizard
This is very close to the setup I have. The differences are that I'm running 2 of the LV6548 configured split phase for 240V and I went with a Siemens 100 amp 3 pole double throw manual transfer switch. The biggest reason I went with that switch was because it's what was readily available, plus it would let me build out something bigger down the road I suppose. I wanted the 3 pole so that I'm switching the neutral along with L1 and L2. I know some here have done this with a 2 pole but it just doesn't seem safe to me. If you're never going to add another inverter and split phase then a 2 pole should be fine. I had a 300A ANL fuse but after watching one of Will's videos I just got a 300A T class to replace it. I'm right there with you on the reason for the transfer switch. It was a lot of money but if I have a catastrophic failure on the solar side, or just want to do some major upgrades down the road, it's going to be easy to flip everything back to the grid while I'm fixing or upgrading. Other than the wire size issues John pointed out I don't see any obvious problems with your design. I got most of my design from Will's videos so I guess it's actually his design with a few tweaks by me. Gotta love this forum!
ghostimage
New Member
My rule are always use the biggest conductor you can fit in a terminal on any given device. (YMMV). However size the breaker and fuse according to device specs, that way your voltage drops and chances of melting the wire are minimal( you job to makesure your overcurrent/overvoltage protection kicks in first). I believe that it is better to run equipment at about 80-90% capacity, then hopefully it will last you longer. So if you do that you can get smaller fuse/breaker.
Wire sized according to amps it carries, breaker and fuse are there to protect the wire so it doesn't start a fire.
I think your diagram looks good. As for transfer switch, I'm with Mr Sparky. I'd spend 1000$ elsewhere. Unless money is not a problem.
Hope it helps and makes sense.
Best regards, Ghost.
Wire sized according to amps it carries, breaker and fuse are there to protect the wire so it doesn't start a fire.
I think your diagram looks good. As for transfer switch, I'm with Mr Sparky. I'd spend 1000$ elsewhere. Unless money is not a problem.
Hope it helps and makes sense.
Best regards, Ghost.
What am I missing. Where is the grid tie input
Is $$ the only issue for installing a fuse instead of a resettable breaker? How often would the fuse blow ( I know hard to tell)?
EastTexCowboy
Solar Wizard
From what I've learned here on the forum, a breaker can actually arc and fuse solid. Beyond that the fuses themselves are relatively inexpensive to replace. But no, the $$ was not a factor at all. I do have an additional 150A breaker between the positive bus bar and each inverter. So it goes from batteries to T Class fuse to bus bar then split to two inverters with a breaker on each. Maybe overkill but that's how Will has configured several in his videos and what has been recommended to me by some of the gurus on the forum. When these guys give me their expert advice I tend to take it. I actually asked the same question before I did the build and added the fuse. Ideally, I should never blow the fuse, but I feel much better knowing it's there.
EastTexCowboy
Solar Wizard
I do have grid tie input, but that won't help me if I have a catastrophic failure on an inverter or if I need to do any major work that requires extended down time. The transfer switch allows me to flip everything back to grid should the need arise. In my case the grid service panels are on the opposite side of the garage from my solar setup - I just didn't have the room to do it any other way. So moving the circuits from the solar panel back to the grid panel would be a major hassle. Kinda like the fuses and breakers, I hope I never really need it but I want it there in case I do. I'm planning on getting a spare inverter sometime down the road and putting it on the shelf as a backup. Maybe even two. I like redundancy.
Didn’t see it on the diagram
