Solark 15k on 400A service

[BackyardBandit]

Hi, I am designing a project (not my own) and looking for some guidance.

Homeowner has a 400A service that is split into two 200A panels off the meter. Homeowner wants a Sol-Ark 15k with 12x EG4-LL batteries for backup (2 stacks).
Customer does not wish to add a PLP or do any load management (despite my recommendation). Their plan is to manually switch off heavy loads should the grid fail to not overload the inverter. Those circuits would be identified and clearly labeled in advance. This home is grid-tied. Everything must be properly permitted and interconnected.

Is it possible to power both 200A panels from a single Sol-Ark 15k? And how would that be wired?

I'm having difficulty sourcing a one-line to pass along to engineering... makes me think it's not possible, or they need a second inverter.

 

[mciholas]

Their plan is to manually switch off heavy loads should the grid fail to not overload the inverter.

That's stupid.

At the moment of grid failure, the likely outcome is the inverter will be overloaded with the current loads (nothing switched off) and thus the inverter will fault out. You get effectively no backup as grid failure causes inverter failure.

There is also the issue that the inverter can't pass 400 amps, so that' a non starter.

If the inverter tries to restart automatically, all the heavy loads are still there (maybe more so as HVAC and water heater now might be active with thermostats sensing more demand). So the inverter will fail to start and subject the house to momentary brown out conditions while it tries.

A far better plan is to group the critical circuits into one panel on the inverter output such that the inverter will very likely pull the load. Then there is much less danger of an inverter overload, and no need to be flipping a ton of breakers in the dark to restart the inverter.

The only downside to this is you can't pick and choose what to backup, it was wired that way from the start.

You could put two inverters, one for each panel. They still won't be able to handle the loads at moment of grid failure with some probability but maybe one will and the other won't, then you can reconfigure breakers and make it work. This requires minimal circuit moving but you have to intercept the panel power at the input side. Each inverter can handle 200 amps transfer, though. I believe each side can share the battery, and thus share the PV charging.

Another idea is to put a 200 amp rated manual transfer switch on each panel that selects between grid and inverter output. Inverter needs to be powered from the grid prior to the transfer switches (separate sub panel). When power fails, an optional minimal critical panel is powered by the inverter (some lights, Internet, etc). The property owner then reconfigures the breakers in the main panels, flips both transfer switches, and now has power to what they selected which could be anything in the house.

I would not design a system that will overload the inverters routinely. That's just bad form.

Mike C.

 

[BlindBadger]

Isn't the 15k only 200A pass through? With that, I'd assume you'd need two at that point (one for each of the 200A panels) or else only have it protecting one panel.

 

[wpns]

15K is only 62.5 amps, if he’s really using a significant fraction of a 400A main then he needs to beef up his inverter size, probably by paralleling multiple inverters.

When we had a generator that couldn’t run everything we had a shunt trip breaker that dropped out a ‘non-critical-loads’ panel so you could do manual load management if you needed to, maybe he could do something like that?

 

[DIYrich]

Isolation Switch after the Meter before split to 200a panels

Put CT on Grid line before Split to 200a panels.

Panel Line to each panel (come in on opposite end from the grid)
Combine Panel lines into one Sol-Ark line.

Transfer switch to select the Sol-Ark Line to go the Grid Input or Load Output of the Sol-Ark

Normal operation (sol-ark exports to its grid line whatever is produced through the 200 Amp Panels). You can use CT's to Limit Power to Home.
Isolation Switch closed (enable power from Grid)
Transfer Switch to Grid Input of Solark

Grid down (sol-ark powers loads on the 200 amp panels):
Isolation Switch Open (detach from grid).
Transfer Switch to Load Output of Solark

Situation you want to avoid: Grid connected (Isolation Switch Closed) to Load Input of Sol-ark. Don't know what would happen.

Note: This requires manual transfer to off-grid.
Better solution: Two 15k's in parallel wired the normal way.

 

[BackyardBandit]

That's stupid.

Agreed.

 

[edward4]

So I have the same setup with two 200A panels off the meter box. Completely electric house. I installed a sense energy monitor with the second set of CT's connecting both panels and have been monitoring my usage for over a year now. My all time peak is 22KW. Electrician clearly overrated the entire system (for future use?). I would suggest that the OP's customer monitor usage for some time and see how close they come to 160A continuous usage.

 

[BackyardBandit]

So I have the same setup with two 200A panels off the meter box. Completely electric house. I installed a sense energy monitor with the second set of CT's connecting both panels and have been monitoring my usage for over a year now. My all time peak is 22KW. Electrician clearly overrated the entire system (for future use?). I would suggest that the OP's customer monitor usage for some time and see how close they come to 160A continuous usage.

Good to know. Probably a dumb question, what is the significance of the 160A?

 

[Nobodybusiness]

Hi, I am designing a project (not my own) and looking for some guidance.

Homeowner has a 400A service that is split into two 200A panels off the meter. Homeowner wants a Sol-Ark 15k with 12x EG4-LL batteries for backup (2 stacks).
Customer does not wish to add a PLP or do any load management (despite my recommendation). Their plan is to manually switch off heavy loads should the grid fail to not overload the inverter. Those circuits would be identified and clearly labeled in advance. This home is grid-tied. Everything must be properly permitted and interconnected.

Is it possible to power both 200A panels from a single Sol-Ark 15k? And how would that be wired?

I'm having difficulty sourcing a one-line to pass along to engineering... makes me think it's not possible, or they need a second inverter.

I put in a Ronks Service entry rated 400 amp manual Transfer switch.

Grid one side and solar the other.

If you did it this way then just get another 15k run them in parallel on the solar side.
Do a line side tap from Meter pan to the Sol-ark grid inputs with a Disconnect between the Meter pan and Inverters.

Doing all this and just having 1 Sol-ark 15k seems to defeat the purpose.
Have 2 and run whole house.

 

[BackyardBandit]

I put in a Ronks Service entry rated 400 amp manual Transfer switch.

Grid one side and solar the other.

If you did it this way then just get another 15k run them in parallel on the solar side.
Do a line side tap from Meter pan to the Sol-ark grid inputs with a Disconnect between the Meter pan and Inverters.

Doing all this and just having 1 Sol-ark 15k seems to defeat the purpose.
Have 2 and run whole house.

Thanks, after multiple discussions we are now planning for dual inverters.