SPlice/Tap for 8AWG PV source circuit run into two 10AWG max terminal connections

[solarken]

I would like to understand if there is any 2023 NEC violation for using an insulated 600V Polaris 3-position tap connector installed in the wiring box of an Inverter to transition the 8AWG run from the array to two 10AWG conductors into two input terminals of the inverter. The tap would be located close to the terminals, with less than 12 inches of 10AWG. The Isc of the 2 strings combined that are feeding the 8AWG feeder is 21.16A,, and so the Imax is 1.25 x 21.16 = 26.45A, and the Ampacity required is 1.25 x 26.45 = 33.06A. I looked for busbar fingers with a lug compatible with the terminal blocks (like Midnite has) as an alternative and cannot find any.

 

[ggunn]

I would like to understand if there is any 2023 NEC violation for using an insulated 600V Polaris 3-position tap connector installed in the wiring box of an Inverter to transition the 8AWG run from the array to two 10AWG conductors into two input terminals of the inverter. The tap would be located close to the terminals, with less than 12 inches of 10AWG. The Isc of the 2 strings combined that are feeding the 8AWG feeder is 21.16A,, and so the Imax is 1.25 x 21.16 = 26.45A, and the Ampacity required is 1.25 x 26.45 = 33.06A. I looked for busbar fingers with a lug compatible with the terminal blocks (like Midnite has) as an alternative and cannot find any.

If the input terminals are DC inputs to separate MPPT channels of the inverter, then no.

 

[solarken]

If the input terminals are DC inputs to separate MPPT channels of the inverter, then no.

This inverter has two input terminals to each MPPT. The two 10AWG conductors would land on the same MPPT. Are you saying that it is not allowed? If so, is there a code reference?

 

[jaggedben]

Just to be clear, this is because the terminals have a 10awg limit, and the inverter manufacturer lacked the imagination to think someone might want to combine strings at the array?

Unfortunately an AHJ could cite parallel conductors smaller than 1/0.

 

[wwhitney]

Unfortunately an AHJ could cite parallel conductors smaller than 1/0.

Are the multiple terminals for an MPPT input obviously in parallel, like a two hole lug? If not, seems reasonable to treat the inverter as a black box, and not ask what is happening inside it. Particularly if the installation instructions cover using both inputs like this.

Or you could use MTW for the #10 AWG and say those conductors are not part of the premises wiring. : - )

Cheers, Wayne

 

[ggunn]

I would like to understand if there is any 2023 NEC violation for using an insulated 600V Polaris 3-position tap connector installed in the wiring box of an Inverter to transition the 8AWG run from the array to two 10AWG conductors into two input terminals of the inverter. The tap would be located close to the terminals, with less than 12 inches of 10AWG. The Isc of the 2 strings combined that are feeding the 8AWG feeder is 21.16A,, and so the Imax is 1.25 x 21.16 = 26.45A, and the Ampacity required is 1.25 x 26.45 = 33.06A. I looked for busbar fingers with a lug compatible with the terminal blocks (like Midnite has) as an alternative and cannot find any.

Would it really be too painful to just run the strings independently all the way to the inverter? That is obviously what the inverter designers had in mind.

 

[jaggedben]

Are the multiple terminals for an MPPT input obviously in parallel, like a two hole lug? If not, seems reasonable to treat the inverter as a black box, and not ask what is happening inside it. ...

I agree. If it came up that's what I'd argue. To be clear I see no real world issue but the OP asked about code.