AC feeder voltage drop exceed 2%

[forumGuy]

I'm in California, using a SE17.3KUS inverter that has an AC voltage drop of 2.40% and the DC voltage drop is .58%. Combined they are less than 3%. Is this acceptable and/or pass code even though the AC voltage drop exceeds the typical 2% practiced? The inverter is as close to the combiner panel as possible and I'm using a #6 which is the largest AWG the inverter allows.

 

[wwhitney]

The NEC has no mandatory limits on voltage drop.

The 2025 California Energy Code does have a limit for Nonresidential, Hotel/Motel Occupancies, and Multifamily Buildings; no requirement for Single Family Residential. That requirement reads:

130.5(c)/160.6(c) The maximum combined voltage drop on both installed feeder conductors and branch circuit conductors to the farthest connected load or outlet shall not exceed 5 percent.

Not sure if/how this is typically applied to PV circuits.

Cheers, Wayne

 

[tortuga]

Technically Cal. Code Regs. Tit. 25, § 1146 covers Voltage Drop in mobile home parks, same general rule 5% total.
I have never done residential in CA so I have not looked thru all their residential codes and regs, then there are local amendments.
NEC Article 647 has a voltage drop mandate but its only for 60/120V systems, although rare I have installed them.
Fire pumps Article 695 had a voltage drop requirement for pump starting, but I have not checked lately.
enforcement of VD is all over the map, but as a designer its good to CYA.

 

[forumGuy]

The NEC has no mandatory limits on voltage drop.

The 2025 California Energy Code does have a limit for Nonresidential, Hotel/Motel Occupancies, and Multifamily Buildings; no requirement for Single Family Residential. That requirement reads:

130.5(c)/160.6(c) The maximum combined voltage drop on both installed feeder conductors and branch circuit conductors to the farthest connected load or outlet shall not exceed 5 percent.

Not sure if/how this is typically applied to PV circuits.

Cheers, Wayne

Thank you for the information. This is a multifamily project. Normally I use 2% for the AC voltage drop and try to stay within 3% combined. Its a typical was of designing PV but I wanted to see if that was concrete or just goo practice.

 

[jaggedben]

No code rules apply to this. Functionally you want to keep the AC voltage drop low so you don't have voltage out-of-range issues if the utility voltage runs high. I know you said the inverter is already as close to the tie-in point as possible but if you can lengthen the DC run and lessen the AC run that would be better.

 

[tortuga]

Here in Oregon they have some requirements we have to follow to get the state funding from investor owned utilities, its worded like this:

2.6.2 Wires shall be sized to keep voltage drop at or below 2% in the DC conductors from the
array to the inverter. Voltage drop will be calculated using temperature-adjusted Vmp
(max power voltage) of the array for the location’s average high temperature adjusted
with the temperature adders in Table 1 above.

2.6.3 Wires shall be sized to keep voltage drop at or below 2% in the AC conductors from the
inverter to the point of connection.