Separate panels for grid and hybrid inverter

[Tom Pounds]

I may be a newbie to this forum, but I am familiar with wiring, power systems, solar systems, etc. being an electrical engineer with additional practical experience of doing many household electrical additions that didn't require the use of a licensed electrician (, but I also know my limits, the building codes, and when I would need to hire an electrician).

I want to bounce this idea off of this group.

My idea is to install another circuit breaker panel next to the existing 200A 36-breaker panel in the house (it is a big house). It would be installed flush mount in the wall one stud next to the existing panel (I'd need to check on code for that to see if that spacing is allowed). The two panels should be close, though, because I would need access to the existing romex wires in the existing main panel. I would choose certain critical circuits from the main panel, disconnect them from their breakers and even pull a pair of those breakers (explained later). The critical circuits would include outlets with refrigerators, freezers, heating and cooling units, microwave oven, strategic lighting around the house, etc. The total load for just these critical circuits would have to be limited to, perhaps, 60 or 70 A. By pulling the romex from the main panel, there should be enough length to re-route them to the adjacent new panel, each circuit with their own new circuit breaker as they were in the old main panel. A pair of breakers would be taken from the main panel (now that I have lots of empty breaker space) and replaced with a 60 or 70A double breaker (240V/120V) that would feed the AC input of a properly sized hybrid inverter. The 240VAC output of the hybrid inverter would then feed the new panel main breaker (60 or 70 A) which would feed the critical circuits. Several 1000 W of solar panels would also be connected to the hybrid inverter, as well as a multi-kWhr battery bank (voltages depending on the inverter requirements, etc.)

The hybrid inverter would be located physically close to the breaker panels, and the inverter would "choose" the best source of power at any given time; solar, battery, or grid, and keep the critical stuff alive all the time.

The wiring could be all done by me, safely, because I would be working on the house side of my main 200A breaker. I would only need to pull a permit and get the inspection.

This would never tie my solar system or batteries into the grid, so my meter would never run "backward".

Thoughts and comments?

TIA

 

[Ampster]

I have a similar setup and I took a page from the book of Tesla and other installations which i have seen. That involved the use of a wiring gutter surface mounted above both panels. That facilitated the routing of the circuits to either of the panels and the flexibility of changes afterwards as my needs changed. Gutters offer the ability to do splices that may not be permitted in panels. In my case i surface mounted the gutter and new panel. I used plywood backer which covered the holes in the drywall.

 

[Tom Pounds]

I have a similar setup and I took a page from the book of Tesla and other installations which i have seen. That involved the use of a wiring gutter surface mounted above both panels. That facilitated the routing of the circuits to either of the panels and the flexibility of changes afterwards as my needs changed. Gutters offer the ability to do splices that may not be permitted in panels. In my case i surface mounted the gutter and new panel. I used plywood backer which covered the holes in the drywall.

That will certainly help facilitate moving the critical wires from one side of the stud to the new side. It's also good to know that this has been done, before, although I never thought my idea was unique. I'll research that "book of Tesla".

 

[the_colorist]

book of Tesla

LOL.

@Tom Pounds What hybrid are you looking for this? Depending on the inverter(s) you select, you would have the ability to place a CT on your drop between the meter and your primary load center. This would allow you to not only backup your critical loads but grid-zero (full or partial) your entire home if you prefer. Even at night.

There are a few different configuration options that you could apply to the non-critical house loads such as PV-only, PV+Batt, etc depending on how much you wanted to reduce your overall electric bill. Assuming that's of any concern.

 

[svetz]

Why go through all that? I'm not sure what you're trying to accomplish by it. If you elaborate we might have some alternate ideas.
For example...

... The critical circuits ... Why have critical circuits at all? Mine is setup as shown to the right. Currently I manually switch things off at the breaker panel if I don't want power there. Eventually I plan to use a "smart" system to turn on/off things depending on excess solar (e.g., turn on the hot water tank or eCar if the system would otherwise throttle back the solar panels).

​

This would never tie my solar system or batteries into the grid, so my meter would never run "backward".

Why not tie into the grid?
Most states in the U.S. have somewhat decent net metering agreements, and most quality inverters have controls (e.g., zero export) for locations that don't.

 

[Ampster]

I'll research that "book of Tesla".

Haha. That was a figure of speech from when I first noticed gutters and grey gateways on the outside even when Powerwalls were installed inside. It turns out I now notice them a lot on commercial work and inverter installations on Youtube.

 

[SolarDV]

I want to bounce this idea off of this group.

TIA

Tom,
What did you finally end up doing?!
Dave