Sol-ark 15K grid-tie whole house backup AC disconnect requirements

[IllDoItBetter]

The engineer designed the below diagram for my system to include in the permit package, he is saying that the AC disconnect has to be fused at 80A per code. This is confusing to me because the inverter has 200amp passthrough when load is beyond the inverter 15Kw capacity. Will this proposed fused AC disconnect allow for 200amp passthrough? Can the fuse be one directional (meaning only for when the inverter is feeding back to the grid, but not fused from grid to inverter). I'd appreciate any help here

 

[mikeenea]

Sol-Ark 15K Manual on page 53, diagram 7 has the design you are looking for. Fused disconnect goes right after the meter and before anything else. the 2nd disconnect is for the inverter grid and not fused.

 

[BMEP]

@IllDoItBetter Your diagram looks very close to the diagram on p53 of the manual https://www.sol-ark.com/wp-content/uploads/2024/06/SK140-0001-002-15K-2P-N-EN-Manual.pdf

Mine is setup the same as this (though I have 2 inverters in parallel so my reference is page 54 int he same manual).

Sure looks to me like your engineer doesn't understand the whole-home backup concept where 100% of power flows through the Sol-Ark. If you use 80A fuses in that disconnect, while using the inverter, the max current coming into your house will be limited to 80A, not 200A like the service allows. It looks like he's thinking of this setup more like a conventional line-side connected "backfeed" solar. He needs to understand that in the whole home backup scenario, 100% of current to the load (house) passes through the Sol-Ark.

The fuses in the disconnect (you have highlighted) and the wires connecting to the meter/service, running to that disconnect and from the disconnect to the Sol-Ark also need to be sized for 200A.

I'd suggest showing him that diagram on page 53 and ask him how the house could draw over 80A if that disconnect had 80A fuses in it.

 

[IllDoItBetter]

Thanks guys. I get what you're saying on the fuses. And I already shared the sol-ark suggested diagram with the engineer before he provided this design.

@BMEP Even though the wires are numbered differently, the specification shows that the wires used are the same. Both ID 2 and 3 wires (4/0) are capable of 200A. Table provided below.

I'm going to ask him to change the min OCPD to 200A for wire ID 02. Would i be correct that the continuous and max current need to also change for wire ID 02 and 03?

Another thing, when i asked to include a fused service disconnect, the engineer interrupted me to say that it is not needed. The service "entrance rated" bypass switch and the AC fused disconnect should be enough. I get what he says but honestly I'm starting to get worried about compliance and delays in commissioning this.

 

[BMEP]

I get it now - seeing that chart - CONT. CURRENT he has at 62.5A, which, coincidentally, is 15kW for 240V. I believe he's only considering the max inverter output of 15kW/62.5A and maybe not realizing that the inverter has 200A pass-through capability. I can see how somebody could easily misunderstand that. Maybe point out the pass-through spec on the Sol-Ark datasheet? (see below).

For what it's worth: my opinion is that it will serve you best to help your engineer get on-board with changing the fuse rating and do it him/herself rather than just doing it because you requested it.

I should also say that the things I've said are just my view based on experience but I am not an electrician or engineer (and did not stay at a Holidy Inn Select last night: