1qqq
Member
- Location
- United States
- Occupation
- Solar Designer
Hello everyone. I am seeking help for this AHJ Feedback. What do I need to do to resolve this? So sorry not very savvy with electrical stuff. Please help.
Need Help with SLD and AHJ Rejection
- Thread starter 1qqq
- Start date
ron
Senior Member
- Location
- New York, 40.7514,-73.9925
They are looking for a load calculation based on article 220 for the 200A backup panel, so they can see the amount of source you are providing via battery is enough to cover the total load, or you will need to load shed.
1qqq
Member
- Location
- United States
- Occupation
- Solar Designer
jaggedben
Senior Member
- Location
- Northern California
- Occupation
- Solar and Energy Storage Installer
Your best bet may be 220.87, showing the existing load.
Since the solar is not a guaranteed source looks like your proposing to automatically transfer a 200A panel to a 5kw supply?
If I had a 5kw backup source I'd be inclined to move 5kw of critical loads to a critical loads panel and have the power wall supply that.
I am not sure how the power wall works can you delete the tesla whole house ATS and add separate critical loads panel directly off the power wall and make sure the load in the cirtical loads panel is =< 5kw?
If I had a 5kw backup source I'd be inclined to move 5kw of critical loads to a critical loads panel and have the power wall supply that.
I am not sure how the power wall works can you delete the tesla whole house ATS and add separate critical loads panel directly off the power wall and make sure the load in the cirtical loads panel is =< 5kw?
jaggedben
Senior Member
- Location
- Northern California
- Occupation
- Solar and Energy Storage Installer
The Tesla Gateway would still be required, but it does not have to backup the whole house. Doing a critical loads panel instead of whole home backup could complicate 705 compliance (120% rule or alternatives) but is probably still doable somehow.
PWDickerson
Senior Member
- Location
- Clinton, WA
- Occupation
- Solar Contractor
You are a solar designer. How is it that you are not savvy with electrical stuff? I would suggest taking a CE course on article 220 (load calcs). Very important for folks designing battery backup systems.
The inspector asked for a load calc for the serivce in the upper note, but the lower notes indicate that he is really wanting a load calc for the backup loads. He pointedly asked that the load calc include battery charging, which will be an added load at the serivce (if the system is programmed to allow the battery to be charged from the grid), but not at the backup loads panel. Seems like you will need to provide two load calcs. One for the service that includes battery charging, and another for the backup loads. The load calc for the backup loads panel shouldn't be over 5 kW, and it almost certainly will be if this is for a typical residence. Your options will be to add more Powerwalls or just backup a subset of the home loads as other have suggested. Or maybe you can figure out how to load shed the large loads.
The inspector invoked the amendment to 710.15(A), but I don't think that was necessary since 702.4(B) already says that optional standby systems (like this one) shall be sized to the load when automatic transfer equipment is used.
The inspector asked for a load calc for the serivce in the upper note, but the lower notes indicate that he is really wanting a load calc for the backup loads. He pointedly asked that the load calc include battery charging, which will be an added load at the serivce (if the system is programmed to allow the battery to be charged from the grid), but not at the backup loads panel. Seems like you will need to provide two load calcs. One for the service that includes battery charging, and another for the backup loads. The load calc for the backup loads panel shouldn't be over 5 kW, and it almost certainly will be if this is for a typical residence. Your options will be to add more Powerwalls or just backup a subset of the home loads as other have suggested. Or maybe you can figure out how to load shed the large loads.
The inspector invoked the amendment to 710.15(A), but I don't think that was necessary since 702.4(B) already says that optional standby systems (like this one) shall be sized to the load when automatic transfer equipment is used.
wwhitney
Senior Member
- Location
- Berkeley, CA
- Occupation
- Retired
I can argue that an MID is not transfer equipment. The definition of "Transfer Switch" in Article 100 refers to "transferring one or more load conductor connections from one power source to another." While with an MID you are just disconnecting one of two simultaneously connected power sources. It's the difference between an DPDT switch and a DPST switch.
So I do think that Dallas's amendment to 710.15(A) is critical for the OP.
Cheers, Wayne
With a Microgrid Interconnect Device (MID), the net result is transferring load from one power source configuration to another configuration in terms of capacity of the source. Source 1 is a utility transformer + Solar & 5kva Battery. Source 2 is solar & 5kva Battery this happens fast enough that most devices won't turn off so I'ds say its a ATS in that its transfering some of the load off the grid, but the definition of ATS might need some updating in the code.
wwhitney
Senior Member
- Location
- Berkeley, CA
- Occupation
- Retired
I will agree the power source configuration is changing, but it's not a transfer "from one power source to another". It's a change (or even transfer if you like) from "two power sources" to "just one of those power sources." Clearly a case not covered by the language in the definition of "transfer switch."
The 2026 NEC First Drat basically removed all of 710.15. I'm not clear on what the intended effect of that change is.
Cheers, Wayne