AC verses DC for 200 foot run

[Michael.J]

I am mounting solar array on my Barn that is 200 foot from my house.
Should I mount the Hybrid inverter in the barn and transmit AC instead of running the DC current to my house from the array?

 

[hwy17]

In off grid we normally like to run DC over that distance because it's higher voltage if you run 6-9s strings.

If you are going to get inspections, the NEC and inspectors are both friendlier to AC and nervous about DC, so the consideration gets more complicated.

The other thing is with hybrid inverters it would mean running both ways, grid power out to the inverter in the barn and then all the load power coming back. But with aluminum wire it's not necessarily that expensive.

 

[DougfromdaUP]

Run the higher voltage farther.

 

[Watts Happening]

In the end it should be far simpler to run a single or maybe two pairs of PV wires back from the barn. Run at something close to 500v and you’re miles ahead.

 

[再生可能 エネルギー]

In the end it should be far simpler to run a single or maybe two pairs of PV wires back from the barn. Run at something close to 500v and you’re miles ahead.

For a DIY, I would not be too confortable with such high voltage because of arcing and fire risk, I would prefer running two strings of 250V.
But this depends also of how much current and voltage your SCC(s) can handle.

Do you plan to use rapid auto-shutdown devices at the panel level?

 

[Watts Happening]

For a DIY, I would not be too confortable with such high voltage because of arcing and fire risk, I would prefer running two strings of 250V.
But this depends also of how much current and voltage your SCC(s) can handle.

Do you plan to use rapid auto-shutdown devices at the panel level?

I suppose everyone has to operate within their comfort zone. I don’t personally have any qualms regarding higher voltage, I sure as heck don’t work on it live.

I have rapid shutdown at all panels mounted to our home, not on panels on our pergola as it is not required.

 

[seneysolar]

PV wire is cheaper than 4 conductor UF wire. Try to use higher voltage strings, use the max voltage input for the charge controller rating and run the PV the long distance.

 

[Zwy]

I am mounting solar array on my Barn that is 200 foot from my house.

Rapid shutdown at panel level is required.

Should I mount the Hybrid inverter in the barn and transmit AC instead of running the DC current to my house from the array?

I use high voltage DC to run to my house 420 feet from the array.

Wire costs more with lower voltage AC, you might need 4AWG for 100A AC while running PV high voltage of 400V only needs 10AWG.

I know which one I'm spending my money.

 

[Zwy]

PV wire is cheaper than 4 conductor UF wire. Try to use higher voltage strings, use the max voltage input for the charge controller rating and run the PV the long distance.

You and I are in agreement on this.

 

[timselectric]

Plain and simple.
Run the highest voltage, the longer distance.
AC or DC, which ever is highest.

 

[zanydroid]

Would the consideration change if the barn anyway needs AC power?

(OP also didn't say how big the array is, if this is a grid tie array of 5.7kW-AC then the direction of this discussion is pretty silly.

Also Hybrid implies off-grid capability and desiring to use that in the house automatically forces the decision of putting it at the house because most hybrid systems of this year's vintage only support built-in transfer switches. IMO these discussions need to focus more on the easy snap decision points)

Rapid shutdown at panel level is required.

Do RSD transmitters have signal integrity for this distance of run? Looks like APSystems says 1000ft out & back distance.

 

[Zwy]

Do RSD transmitters have signal integrity for this distance of run? Looks like APSystems says 1000ft out & back distance.

I can't say as I do not use roof mounts. I prefer to not have to implement RSD and add to costs.

 

[MajicDiver]

For a DIY, I would not be too confortable with such high voltage because of arcing and fire risk, I would prefer running two strings of 250V.

It all depends on personal preference and skills. I am using strings with about 500 vdc VOC in cold weather for 3 years now and have no regrets whatsoever.

 

[zanydroid]

Is the fire risk that bad if the wires are, upon reaching structure, encased in SCH80 or EMT?

If the 500V wires arc and burn up in the ground, I don't think it would cause an issue except with an extreme freak accident.

 

[timselectric]

Don't run a old rusty gas pipe in the same ditch. And you should be fine.

 

[再生可能 エネルギー]

Is the fire risk that bad if the wires are, upon reaching structure, encased in SCH80 or EMT?

If the 500V wires arc and burn up in the ground, I don't think it would cause an issue except with an extreme freak accident.

I would be more concern with the arcing risk at each end of the line than underground.
Performing the installation after dark would be recommended,

But if you needed to turn on or off the PV line or disconnect some panels during the day,
there are some precautions to take, such as wearing high voltage gloves and protection glasses.

If you have rapid shutdown this would be less of an issue,
but this might not be the case for a installation on a separate barn.

 

[Bluedog225]

Subscribed. I’ve got exactly 200’ from my conex to the cabin. I don’t recall exactly, but the wire needed for one or two 5000 watt inverters at 120 volt wasn’t that expensive. Will double check when I’ve got more time.

 

[wpns]

Another vote for RSD at the panel level and high voltage DC back to the house.

If you need AC at the barn run AC to the barn separately.

 

[addision]

Who is drawing up your plans? I do 90% of my work, even if I don't have it inspected I want it to code. It is cheap to get someone to design a system and stamp the plans these days (engineer). What do your inverters prefer?

I went with DC because the conductor size would be smaller and a lot less expensive. I put in a larger conduit for future expansion if I needed it. Pulling larger conductors over that length can be done, but it is a lot less work pulling smaller wires. Also, my inverters will only take up to a certain gauge wire as an input. You should check on that first.

 

[zanydroid]

+1 to just having someone draft it after you do a design sketch and then quality control it. It’s very high value for dollar vs your own time to learn how to do it to the same level of professionalism.

And that’s even for drafting for your own use. If drafting for submitting for permits, there is so much minutiae expected in some places, that is auto form filled by the plans service you pay for , but you have to figure it out slowly and painfully