Solar Battery wiring specs - Manufacture citing NEC rule i cannot find

[Jeremybme]

I am in the process of wiring up a solar battery to a solar system.
the manufacture has sent me the following info
charge / discharge is 20 A at 350Vdc. The PEAK current (only discharging is 32.8A for 10 seconds max
They then stated that #10 AWG could be used because of some NEC rule allowing +- 25% since the 32.8 amps would be very rare (only if power failed and lots of big devices tried to start at once (HVAC, Water heater etc) and only for 10 seconds at a time. I dont see that +- 25% rule anywhere

The plan was to hook 2 of these up. Running THHN wire in a conduit. There will be 6 wires total in the conduit. two of which are ground wires.
It appears to me that #10 THHN would be rated at 40 amps but then using the derate because there is 4 current carrying conductors of .8 we end up at 32 amps per wire. just shy of the 32.8 peak possibly amps. is this allowed? or should i go ahead and use #8 awg THHN to be safe. its been a while since i took my electrical classes and ive moved on to other line of work so im not fresh on all the NEC rules.

 

[jaggedben]

The NEC generally doesn't require peak current ratings to be used to size circuit conductors. Without seeing how the datasheet characterizes the various current readings it's a little hard to be sure, but it sounds like your conductors would only be require to be sized for 20A. (Or possibly for 25A, i.e. 125% of 20A if operating might be continuous for 3hrs plus.) I think 10awg is most likely completely code compliant.

 

[Jeremybme]

The NEC generally doesn't require peak current ratings to be used to size circuit conductors. Without seeing how the datasheet characterizes the various current readings it's a little hard to be sure, but it sounds like your conductors would only be require to be sized for 20A. (Or possibly for 25A, i.e. 125% of 20A if operating might be continuous for 3hrs plus.) I think 10awg is most likely completely code compliant.

Thank you!