Two service panels load calculations with solar

[Scott Franklin]

Hello,
I am a solar sales, marketing, and office manager.
I am not an electrician or contractor. But I am here to learn.

I have a client with 1 meter feeding 2x 150A service panels.
We installed solar with batteries.
-Our engineer calculated the full Sqft of the home in the load calculations for each panel.
-They also calculated the same circuits on each panel even though they only exist on one panel.
-They calculated the potential load of three AC units when their actual amperage is much lower.
See link to picture for clarification.

Questions:

1.) can we split the square footage of the house between the 2 panels??

2.) are the circuits supposed to be the same on both panels?

3.) are we supposed to factor in potential AC loads? Or do we go based off what the nameplate says?

Thanks for any help. Google Drive Link

 

[Dennis Alwon]

I don't think there is any code section that will help with this issue. IMO, you could calculate most of the circuits in a panel by seeing what each panel controls. For instance, if one panel has all the kitchen circuits then I wouldn't consider that when calculating the other panel. The actual 3 watts/sq.ft doesn't make a huge difference since you have the demand factor available. I guess you can see if, in fact, the breakers in one panel cover about the same area as the other panel and then use half.

 

[Dennis Alwon]

A/C load is based on nameplate

 

[Scott Franklin]

A/C load is based on nameplate

Thank you for your replies, I really appreciate it

 

[jaggedben]

Hello,
I am a solar sales, marketing, and office manager.
I am not an electrician or contractor. But I am here to learn.

I have a client with 1 meter feeding 2x 150A service panels.
We installed solar with batteries.
-Our engineer calculated the full Sqft of the home in the load calculations for each panel.
-They also calculated the same circuits on each panel even though they only exist on one panel.
-They calculated the potential load of three AC units when their actual amperage is much lower.
See link to picture for clarification.

Questions:

1.) can we split the square footage of the house between the 2 panels??

2.) are the circuits supposed to be the same on both panels?

3.) are we supposed to factor in potential AC loads? Or do we go based off what the nameplate says?

Thanks for any help. Google Drive Link

1: I agree with Dennis. Yes, you can divide the square footage, but not just 1/2 for each panel. A proper approach would be something like turning off the general lighting a plug circuits in one panel and adding up the square footage of the rooms, or portions of rooms, that lose general light and plug power. Or, failing that, at least counting the general light and plug branch circuits in each panel and dividing proportionally. As Dennis alludes to, the small appliance and laundry circuits should be counted for the panel they're in.

2: No.

3: Not sure what you mean. You count the existing load by nameplate. If you're making changes you include the nameplate of any new load that is going to be added. You're not required by code to make allowances for hypothetical future load in order to do work now. You'd only do that to answer a client's question about how much load they could add in the future without upgrading the panels or service.

 

[Scott Franklin]

1: I agree with Dennis. Yes, you can divide the square footage, but not just 1/2 for each panel. A proper approach would be something like turning off the general lighting a plug circuits in one panel and adding up the square footage of the rooms, or portions of rooms, that lose general light and plug power. Or, failing that, at least counting the general light and plug branch circuits in each panel and dividing proportionally. As Dennis alludes to, the small appliance and laundry circuits should be counted for the panel they're in.

2: No.

3: Not sure what you mean. You count the existing load by nameplate. If you're making changes you include the nameplate of any new load that is going to be added. You're not required by code to make allowances for hypothetical future load in order to do work now. You'd only do that to answer a client's question about how much load they could add in the future without upgrading the panels or service.

Thanks for the reply