300Amp service design for home w/future solar panels

[dclauria]

I am bidding a home in Michigan for which the plans show 3 solar panel arrays on the roof - 10x10, 14x10, and 20x10.

The home specifies a 300Amp service, and "electrical contractor shall coordinate work with the alternate energy (solar, wind turbine etc.) supplier"
However, I've been told the solar installation is something future that the homeowner will take care of.

I have wired several homes designed by the same architect in the past. He almost always specifies a 300 or 400Amp service, but to keep costs down, we use a POCO 320Amp meter base with double lugs feeding two 200Amp disconnects or panels, depending on location. (On this project the panel location is in the basement mech. room - approx. 50' from service location)

What design info would I need to keep in mind to make it simple to integrate a solar installation w/grid connection? Can I bid my standard 2 loadcenter panel service w/4/0AL SER, or do I need to plan on a 300 or 400Amp disconnect w/conduit & panelboard? - I usually use SqD products.

Thanks for any help from those of you with more experience on this.

 

[augie47]

I think the keywords in your post are "with grid connections".
My first step would be to coordinate with POCO as to their requirements.
Locally most of the "grid connected" systems of the size you mention have separate risers/laterals and metering. If the goal is planning for future alternate energy connection I visualize you having a separate "service" for the moment deadendiing in a disconnecting means, but thats based our local POCO rules.

 

[BillK-AZ]

Possible options

Possible options

Option 1
See if you can get a POCO 320Amp meter base with three-hole lugs that are factory installed. Reserve the third hole for future solar. When the time comes, connect the solar as a line side connection with its own disconnect switch. You can then back feed the utility using inverters with breakers the lesser of 320A or the rating of the disconnect switch.

Option 2
If the proposed future solar can be accommodated by two 40A breakers, one in each panel, just reserve the position opposite from the main panel breaker for the solar in each panel.

Option 3
Use one or two distribution panels rated at more than 200A. They can be fed by 200A main breakers. The sum of the main breaker (200A) plus the PV breaker can be up to 120% of the panel rating. A 225A panel fed by a 200A main breaker can have up to a 70A PV breaker. While 120% of a 350A panel is 420A, the PV limit is the 200A main breaker.

Option 4
There are now some panels and all-in-one service entrances with factory provisions for the line side connections or provision for a large sub-panel breaker.

The above is based on breaker ratings. See the inverter specifications for the required breaker, the actual amps out will be lower.

 

[jaggedben]

I am bidding a home in Michigan for which the plans show 3 solar panel arrays on the roof - 10x10, 14x10, and 20x10.

I assume those numbers are in feet, not panels, right?

If so, you are looking at system in the neighborhood of 6kW dc, give or take a kW or so if all the space is used and none is added. That puts you in the neighborhood of a 30amp or 40amp solar breaker. As Bill said, you can put a 40amp solar breaker in a 200amp panel, and it can be more if the breaker feeding the panel is less than 200A. Leave the end(s) of the load center(s) opposite from where they are fed unused.

I would say you are most likely in good shape with the plan you describe but there is a chance the solar design would hit some limits. Using even a 225A panel(s) would give extra flexibility later on.

Another thing to think about planning for is the GEC for the solar.

 

[glennyamada]

PV breaker rating

PV breaker rating

Where can I find that the PV breaker can be up to 120%, what article states this?

Option 1
See if you can get a POCO 320Amp meter base with three-hole lugs that are factory installed. Reserve the third hole for future solar. When the time comes, connect the solar as a line side connection with its own disconnect switch. You can then back feed the utility using inverters with breakers the lesser of 320A or the rating of the disconnect switch.

Option 2
If the proposed future solar can be accommodated by two 40A breakers, one in each panel, just reserve the position opposite from the main panel breaker for the solar in each panel.

Option 3
Use one or two distribution panels rated at more than 200A. They can be fed by 200A main breakers. The sum of the main breaker (200A) plus the PV breaker can be up to 120% of the panel rating. A 225A panel fed by a 200A main breaker can have up to a 70A PV breaker. While 120% of a 350A panel is 420A, the PV limit is the 200A main breaker.

Option 4
There are now some panels and all-in-one service entrances with factory provisions for the line side connections or provision for a large sub-panel breaker.

The above is based on breaker ratings. See the inverter specifications for the required breaker, the actual amps out will be lower.

 

[don_resqcapt19]

Where can I find that the PV breaker can be up to 120%, what article states this?

That is not exactly correct. The sum of all breakers that feed power to the panel can be no more than 120% of the panel rating. The PV breaker itself cannot be 120% of the rating. In most application there are two breakers involved in this. The main and the PV breaker. If you have a 225 amp panel with a 200 amp main you could use a 70 amp breaker. If that same panel had a 225 amp main, you could only use a 45 amp breaker. 705.12(D)(2)