Small cabin plan

[xy74]

I have all the major components (I think) and wanted to run this plan out for comment. This is 100% off grid, I will install it and this forum will get to inspect it.

Equipment will be in a 3X5 closet. The 3' side is the outside wall and what is represented in the picture. Imagine the cardboard on the floor is a vertical wall. Solar panels will be mounted just outside this wall on a pergola type structure. (eventually) The main AC panel will be on the 5' wall which would be to the left in the picture. The MPPT would be about 70" above the floor. In lieu of cardboard, it will get mounted on cement board in the final install.



Battery to the busbars which feeds the various components. 100 amp fuse to the inverter, 63 amp DC breaker to the MPPT, 30 amp DC breaker to the plug in battery charger (run off generator), single battery so the 100 amp CB on board for the battery. #2AWG for battery and inverter. #10 for the charger, #4 for the MPPT. PV is going to be JA solar 295W used panels, 39.6 VOC, 32 VMP, 9.2 amps. Not sure how many, but initially will try 5 in series. (Nicely stays under the 250V limit) Final configuration TBD based on usage and will add combiner box if needed. Initially the panels will be set out on the ground and wires enter through the wall just below the disconnect. Probably will be plastic conduit or liquid tite. (violation #1, bad idea?) All equipment chassis', PV frames, main AC panel will connect to a common ground bus (not pictured, think it will be between battery and charger) connected to a ground rod driven just outside.

AC will exit the top of the inverter and go to a small distribution panel. Back feed a 30 amp breaker and jumper both legs for 120v. The inverter is bonded, so will leave it that way and not bond the panel. I am not planning a transfer switch for generator.

Some questions. No doubt will have more.

1) Is the battery negative also supposed to be connected to the earth ground (ECG)? Small explanation anyone?

2) Should I exit the PV disconnect in conduit for a few inches up towards the MPPT? Of course at some point the wires do have to see the light of day. Better to just keep it short and skip conduit?

3) This one gets it's own picture. AC output. As pictured it's temporary cord connected to a handy box with a duplex outlet. For the final install, can I use #10 romex, exit into the wall directly (DOWN through cardboard in the picture) and come out around the corner into the main AC panel? Should I be using crimp ends or bare solid wire?


Thanks!!

 

[Rednecktek]

it will get mounted on cement board in the final install.

Be aware that cement board doesn't hold screws for shite. Use thick plywood for the backing with a 1/4" concrete between the wood and equipment. That way your screws can actually hold the load.

1) Is the battery negative also supposed to be connected to the earth ground (ECG)? Small explanation anyone?

No. The battery negative is just to the bus bar. If a device has provisions for grounding, it'll have a post or screw labeled for that.

2) Should I exit the PV disconnect in conduit for a few inches up towards the MPPT? Of course at some point the wires do have to see the light of day. Better to just keep it short and skip conduit?

If you have extra conduit or liquid tight you can, but it's not worth spending money on.

3) This one gets it's own picture. AC output. As pictured it's temporary cord connected to a handy box with a duplex outlet. For the final install, can I use #10 romex, exit into the wall directly (DOWN through cardboard in the picture) and come out around the corner into the main AC panel? Should I be using crimp ends or bare solid wire?

Forks or ring terminals will give you a tighter connection but just stuffing the 10awg in there should work perfectly fine. Yes, you can run it straight out and through the wall as long as you can avoid any bends at the terminals as much as possible. Solid core Romex doesn't crimp all that well so I'd go bare copper for that end.

(violation #1, bad idea?)

Violation of what? It keeps the water and varmints from the wire.

100 amp fuse to the inverter, 63 amp DC breaker to the MPPT, 30 amp DC breaker to the plug in battery charger (run off generator), single battery so the 100 amp CB on board for the battery.

Your breakers all seem a bit undersized. The math is 125% running amperage. The 60a MPPT will be a 75a breaker to the battery, and so on. What's the wattage on that inverter? Your battery is only going to be good for abut 4500w before its BMS trips. A 100a fuse is only good to about 3800w.

Just to throw it out there, since this is a cabin, does it ever get below freezing out there? That battery (AFAIK) doesn't have heaters or low temp protection. Last thing you want is a cold crisp morning sun breaking your expensive battery.

All in all looks like a good plan.

 

[xy74]

Thanks for the feedback.

Yes, am aware the cement board is not too strong and that inverter weighs 70 lbs. I will make sure there are studs to hit.

I think technically the PV is supposed to be in metal conduit, I'll just keep it short.

The inverter calls for a 100 amp fuse or breaker. Rated at 63 amps continuous max input. (2500 watt version) The charger is only 18 amps input, so the 30 amp breaker is appropriate. The charge controller should have a larger breaker in theory, but I will never have enough panels to push it to the max. Plus the midnite solar breakers I am using are rated for 100% continuous load, so went with the largest size they had which was 63 amps. I figure if any of those trip, there are big problems and I will be glad they did trip.

Yes, the battery will get under freezing from time to time. My plan is to have everything off when I am not there, so it will never charge unless I am there to turn it on. Of course there is the the failsafe I would rather not rely on of the BMS won't charge below 32F, nor should the MPPT if I read my instructions properly. The battery will be in living space, so it won't be long after we get there that the wood stove will be warming things up. It's an occasional property. If the weather doesn't look decent, we'll be staying home anyway.