AC feeder voltage drop exceed 2%

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forumGuy

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Estimating
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.
 
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
 
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.
 
wwhitney said:
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
Click to expand...
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.
 
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.
 
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.
Click to expand...

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.
Click to expand...
 
wwhitney said:
I assume you mean no NEC rules? Because it seems like the CEC can easily be read to apply to the OP's question.
Click to expand...

Well, yes, that's at least more debatable than the NEC. I don't think the CEC requirement applies to PV. My reasons for that are 1) that a PV system doesn't really have a 'load or outlet', and there's not really a sensible way to interpret where the load that the PV serves is, 2) not written with DERs in mind, clearly, and 3) not enforced in my experience.
 
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