single family dwelling Max voltage

[Ponchik]

Is there any voltage limitation for single family dwelling?

I have a large solar project that will be about 700' away from the main panel. So to compensate for VD I can install (2) 480V transformers VS doing parallel runs. With the copper prices if I do the transformer route and aluminum conductors i can keep the cost a bit lower and still achieve the same results.

But I don't know if single family has any voltage limitation.

Thanks for your feedback.

 

[rlundsrud]

There isn't a code requirement for voltage drop, but the recommendation is (+-)3%. A 200 amp service with a 700' run would require 400 kcmil copper or 500 kcmil aluminum. I would be surprised if that was more expensive than installing a 480/240 step-down transformer with the associated disconnects that would be required. For the 480 volt system you would still need at least a 3/0 Cu cable to maintain a 3% VD. Price it up both ways and see where the best path lies.

 

[jaggedben]

I think the OP is asking if 480V is prohibited in single family dwellings.

To my knowledge it is not. And if it were, might it be possible to keep it out of the inside of the dwelling?

Also 3% VD might not be advisable in this situation if the utility voltage were to run high, as the inverter(s) would shut off. He could be striving for 1-2% for good reasons.

 

[GoldDigger]

Residential is specifically limited to 600V DC, so in some cases it is better to make long runs at DC when there is a choice of inverter location.

 

[gar]

151218-2355 EST

GoldDigger's suggestion is good because this eliminates the voltage drop on the AC side. On the DC side you probably don't care too much about the voltage drop other than wasted (lost) power. Also the DC voltage from your panels should be higher and thus less current for the same power.

.

 

[ActionDave]

I think the OP is asking if 480V is prohibited in single family dwellings....

It is. Somewhere. I'm not remembering where, which means I would have to look it up and I'm not going to do that now. If I am wrong someone will jump in.

 

[iwire]

The only limitation I know is for branch circuits, 210.6. I am not aware of any for feeders or services.

 

[iwire]

Is there any voltage limitation for single family dwelling?

I have a large solar project that will be about 700' away from the main panel. So to compensate for VD I can install (2) 480V transformers VS doing parallel runs. With the copper prices if I do the transformer route and aluminum conductors i can keep the cost a bit lower and still achieve the same results.

But I don't know if single family has any voltage limitation.

Thanks for your feedback.

I would look into 480 volt (or even 600 volt?) inverters at the array end and just one appropriate transformer at the service end.

 

[Ponchik]

I would look into 480 volt (or even 600 volt?) inverters at the array end and just one appropriate transformer at the service end.

AHHH I never thought about that.

 

[electrofelon]

I would look into 480 volt (or even 600 volt?) inverters at the array end and just one appropriate transformer at the service end.

I do not think you will find single phase 480 inverters.

Im with golddigger - string up the strings with the max voltage you can (which you would typically do anyway) and run the DC back - its already got the high voltage you want. Alimunum is cheap. What is the KW?

 

[Ponchik]

I do not think you will find single phase 480 inverters.

Im with golddigger - string up the strings with the max voltage you can (which you would typically do anyway) and run the DC back - its already got the high voltage you want. Alimunum is cheap. What is the KW?

27 KW system.

 

[ActionDave]

The only limitation I know is for branch circuits, 210.6. I am not aware of any for feeders or services.

That's the one I must have been thinking of.

 

[jaggedben]

Im with golddigger - string up the strings with the max voltage you can (which you would typically do anyway) and run the DC back - its already got the high voltage you want. Alimunum is cheap. What is the KW?

This is probably good advice. There was a paper, which is probably more applicable to utility scale PV, but which may still be relevant, that argued that the extra cost of cable to avoid voltage drop is not justified compared to the gain in production.

Just make sure that the VD doesn't drop you out of the inverter voltage window. (Also if it's Solaredge, it's a different discussion.)

 

[Smart $]

That's the one I must have been thinking of.

Because the discussion has opened up to running a PV output circuit to the house, we should point out 690.7(C) limits the voltage to 600 in one- and two-family dwellings.

As long as the circuits remain outside, there is no limit, though going to over 1000V includes some extra hoops to jump through.

 

[jaggedben]

Because the discussion has opened up to running a PV output circuit to the house, we should point out 690.7(C) limits the voltage to 600 in one- and two-family dwellings.

As long as the circuits remain outside, there is no limit, though going to over 1000V includes some extra hoops to jump through.

Thanks to you, we now need to clarify for sure if the service is single phase or three phase. :lol: You won't find many single phase 1000V inverters.