AC Coupled Battery Backup Install Questions

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ggunn said:
Why would you need specialized AC combiners? We just use regular MLO panels for AC combination.
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It's not so much specialized as done for you. Since the Envoy now needs to be on its own breaker, and in a 12x12x4 PVC box, you save the extra cost of supplying your own subpanel and box and you nearly come out even. Add the occasional instance where you have to make an extra trip to the job because you forgot to supply one of those items yourself, and you come out even more even. It also looks cleaner.
 
The client just closed their solar loan so I am finally able to proceed with this installation. Before I submit for utility interconnection I need to have my electrical 1 and 3 line stamped by my PE, and I will upload my design here so y'all can give feedback.

I am still a bit confused with designing the solar subpanel to be NEC compliant on the load side of the main breaker, but hoping it makes more sense once I go on AutoCAD for a few hours. The easiest solution is to just interconnect on the supply side of the main breaker, but that won't make for a seamless battery installation like I promised the client I would set up this system for with a dedicated solar + storage + critical loads panel.

Putting the solar + critical loads + storage subpanel on the load side of the main breaker requires downsizing the main breaker as previously discussed. Decisions decisions...

-Alex
 
jaggedben said:
As far as the subfeed lugs and breakers, those are all options with their own conderations. But what I had in mind was breakers such as the Homeline 2200BB or the Eaton BJ2200.
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Could you elaborate a bit on what these breakers accomplish? I am having a hard time seeing the application. Does this replace the main breaker and allow a feed thru? How would that accomplish NEC compliance considering the bus bar overloading?

I really appreciate all the help with this project.
 
DeFreitas Enterprises said:
Could you elaborate a bit on what these breakers accomplish? I am having a hard time seeing the application. Does this replace the main breaker and allow a feed thru? How would that accomplish NEC compliance considering the bus bar overloading?

I really appreciate all the help with this project.
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Basically I was just pointing out that your electrician is theoretically right when you made the following statements in your original post...

...My electrician seems to think we will be able to use a 200 amp breaker like any other subpanel install, but I think he may be mistaken here. I can't imagine the size of the terminals to accept the proper sized wire for 200 amps. I have only seen 100 amp breakers, never anything higher....
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He's theoretically right in that 200A branch breakers do exist.
With that said, I've never done an install with these breakers either, because it just seemed unfeasible or not economic compared to other options in residential. Wrestling with 3/0 cu in an existing resi panelboard and possibly splicing it inside an existing enclosure that is already pretty full is not my cup of tea. You've got to be able to actually get cable or conduit in and out; if all the walls are finished you need to be a carpenter, or hire one... I've done the subpanel thing plenty of times with 100-125A but that's often hard at those wire sizes. So I've always done a main breaker downsize or found a way to get to the existing subpanel or something.

Ultimately the best answer will depend on details specific to the job.
 
Okay finally got my design over to the Electrical PE for stamping. We are trying to qualify this under 2017 NEC 705.12(B)(2)(3)(b).

Inverter Output = 1.21 Amps
(53)*1.21 = 64.13 Amps
64.13 * 1.25 = 80.1625

Let's round that down ever so slightly to 80.0

Decrease main breaker size from 200 Amps to 150 Amps.

150+80 = 230 Amps which is less than 120% of 200 amp rated busbar.

Only consideration here is the backfeed breaker needs to be on the opposite end of the busbar if I am understanding the code correctly.

Here is a link to my line diagram design and some site pictures of the electrical room. LMK if this link doesn't work.

https://drive.google.com/open?id=1XueZHFTKyLB4h9x5axGlxIIa4pMo4N_m

-Alex
 
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