Voltage drop calc

[wwhitney]

AC output circuits of PV inverters are considered continuous current sources, which they will be in practice if the DC/AC ratio is high enough. See 690.8(B) and 690.9(B).

Cheers, Wayne

 

[Strathead]

Very in-depth. Thank you for that.

I think I will stick with 75°C to be conservative since there is minimal effect.

Sent from my SM-G998U using Tapatalk

It looks like the little i would be a link to information. Click on it and it should tell you what they are looking form. I am with others, that it may be asking for ambient temperature. I would use max of 70 Fahrenheit if buried, and 100 Fahrenheit if outside.

 

[electrofelon]

Electrofelon, I know what the book says, but the words "continuous load" aren't as obvious. 690.8 seems to apply to the DC side, for instance.
What I am trying to say is that even if the book says solar is a continuous load, it really isn't. Take a look at this solar performance screen shot on three cold February days:
View attachment 2565431
The first day was clear blue sky, and the system produced the classic half sine wave. But its maximum power peaked for only part of one hour.
The second day, some clouds reduced the peak and cut a couple of notches in the sine wave.
The third day, we had snow and that 110kW system barely harvested enough power to brew my coffee.
That is simply NOT a "continuous load."
As I said, we follow the rule but I don't like it and don't think it accurately reflects what really happens. The notorious intermittence of solar and wind harvesters is what drives the 24/7/365 power folks nuts. They need to have a lot of sine curves like day 1, OR zero-days like day 3.. There is no way to throttle up their massive steam turbines to react to the cloud blips in day 2, and line impedances, automatic tap changers, and the like may not even allow them to see those blips.

690.8 has within it "inverter output circuit" which has a definition.

I just don't agree on the ambiguity of PV being a continuous load. For one thing it says right in 690 "photovoltaic system current Shall considered to be continuous", and just because you can cherry pick a snowy wintery day when you don't get 3 hours of full output does not make it a non continuous load.

 

[ggunn]

Electrofelon, I know what the book says, but the words "continuous load" aren't as obvious. 690.8 seems to apply to the DC side, for instance.
What I am trying to say is that even if the book says solar is a continuous load, it really isn't. Take a look at this solar performance screen shot on three cold February days:
[...]
The first day was clear blue sky, and the system produced the classic half sine wave. But its maximum power peaked for only part of one hour.
The second day, some clouds reduced the peak and cut a couple of notches in the sine wave.
The third day, we had snow and that 110kW system barely harvested enough power to brew my coffee.
That is simply NOT a "continuous load."
As I said, we follow the rule but I don't like it and don't think it accurately reflects what really happens. The notorious intermittence of solar and wind harvesters is what drives the 24/7/365 power folks nuts. They need to have a lot of sine curves like day 1, OR zero-days like day 3.. There is no way to throttle up their massive steam turbines to react to the cloud blips in day 2, and line impedances, automatic tap changers, and the like may not even allow them to see those blips.

None of that makes any difference to PV system design. The NEC says that we have to consider the current in PV systems to be continuous because it potentially could be, examples to the contrary notwithstanding.