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410' wire run

jjohan

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I am looking at installing a 15.7kW ground mount, grid tie system. The distance from the array to my house is about 410'. I may expand this system, maybe even double it in size in the future. I am wondering if it is generally better/more economical to run the distance at a high DC voltage or convert to AC at the array location and then run the 410', keeping in mind probable future expansion. Any other general suggestions for this length of run would be welcome.
 
I am looking at installing a 15.7kW ground mount, grid tie system. The distance from the array to my house is about 410'. I may expand this system, maybe even double it in size in the future. I am wondering if it is generally better/more economical to run the distance at a high DC voltage or convert to AC at the array location and then run the 410', keeping in mind probable future expansion. Any other general suggestions for this length of run would be welcome.
I think the answer will be based on voltage of the 410' run. If (for example) you compare 400v DC with 240v AC, the DC will win. If however you compare 400v DC with 480v AC, the AC will win.....in regards to amps and wire size.

I think it will be easier to deal with higher voltage DC than higher voltage AC. If you purchase an inverter that can take 400v+ DC you can just run 400v to the inverter. If you have go to 480v AC and you don't have a 480v service, then you have to step down to 240v when you get to the service point, which would mean a fairly large transformer and transformer loses.
 
A youtube channel where they upgraded to a 13kw PV system with 3 parallel Schneiders with a loooooong wire run from array to power shed. For example, this model of Schneider accepts up to 600vdc - https://solar.schneider-electric.com/product/conext-mppt-charge-controller-2/ Not pushing Schneider, just sharing a visual of an actual solution. They have a pretty complete set of videos - here's one :)
 
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You need to use a voltage drop calculator.

I would not use a transformer. I would put the inverter as close to it's loads as possible. So that means, I would just run the DC.

If you are going to expand, bury multiple cables. At 410 ft and 15.7KW, you are probably into some decent sized wire even at 400-600v.
 
that is a complicated question...
you distance from production to house of 410' means you are looking at a wiring path of over 820'!!
Clearly this is the range high voltage as moving current over such a distance would be a real pain in the wallet.

when thinking of high voltage both AC and DC are quite dangerous, however, keep in mind that when "accidents" happen high AC voltage arcs are easier to extinquish, high voltage DC loves to keep that arc going, even after the wire may have melted that arc may continue!

just some quick math to think about:

16kw / 480V = 33amps; even at that very high voltage you have pretty hefty current flowing.
16kw / 240V(rms) = 66amps..no surprise even running a what is normally considered a max house voltage you are moving a lot of current.

820' of wire is really going to cost you and as you increase the voltage demands beyond 480 to 600v you leave the "cheap commodity" wiring and end up having to by more expensive wire (with 800-1000v ratings)...
It is a trade-off on working voltages of everything involved and the larger gauge that would be need to increase allowable current.

thats a long distance to move so much power...unless you are the power company of course hehe
 
just for fun I went to an online wire sizing calculator, its not the greatest but it is simple enough to get an idea:

with 820' of conductor:
at 33amp current it recommends 0000 wire!! (that is really thick wire, just the core is about 0.5" hehe)
at 66amps it states you should consult an electrician as multiple wires would be needed.

you are probably looking at maybe $2k in just wire for 4/0, ouch
 
I'm not a calculator expert but just taking the above 16kw/480v = 33a you could do 2 strings (4 wires) at 17a each down 6awg or 8awg or something mainstream (good price). Even if you get 5% loss in full sun at that level its not the end of the world. In winter its going to be 25-30% of summer.

I have a 13kw PV system with wire runs of 90-120v@45-50a on 6awg going a 150ft. I have an overall system loss of 19% (as far as I can tell) with 16% of it right from the inverters. Maybe 1% with 18650 charge/discharge - so 2% due to wiring/other.

My point is, there are several factors to an overall system and loosing 5% to wiring (there's nothing dangerous if wire is in spec) could be made up by bigger $ on more efficient inverter. Its easy to get OCD on all aspects of solar and after 3 years of operation I've just had to 'let some of it go' and focus on glass 80% full rather than 20% empty.... the clouds pull down production whether I worry about it or not - and they don't even give notice :)
 
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I'll put this in another light, DC is great but only meant for short distances. Otherwise Edison would have cornered the market and Nikola Tesla would have never invented AC.

You would require a HUGE Copper Cable to carry that amount of DC 500' and I won't even mention EMI/RFI... Goodness Gracious! BTW, DIYsolars guesstimate is LOW, it would require trenching, serious conduits and more.... HINT: I converted Wood Saw Mills to Solar and you wanna see serious DC !

In such instances, the vast majority of people will put together a Powerhouse with Inverter(s) and usually batteries & related and then send AC to home/Shop which can travel great distances with Much Cheaper Thinner Copper. There are also WINS by having a separate powerhouse, ie: the fans & noise, if something goes bad, it's in an isolated building. They can be independently heated to "maintain" above freezing temps but not radically wasting heat for no reason, it only has to be between 40-50F to keep LFP batteries at their Happiest !. Seriously the cost to build a 10'x10 or 8'x12' Building with 2x6 and insulating it and tossing in a small direct vent heater & you are Golden. Hell of a LOT Cheaper than buying massive copper !

EDIT: I should have also mentioned, that SCC's Inverters etc all make heat and it can be quite a bit, so of course in winter that's not a terrible thing but needs consideration in summer... All variable to your locality of course.

BTW: Copper is Flagged for shortages so now costs are really climbing and it is going to get Really Bad in <6 months... You are ALL WARNED !

Hope it helps, Good Luck.
 
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I don't know of a charge controller that will do an entire 15.7KW array. You will probably need 2-3 of the SE MPPT 100 or Midnite solar's Hawks Bay or similar model.
 
I don't know of a charge controller that will do an entire 15.7KW array. You will probably need 2-3 of the SE MPPT 100 or Midnite solar's Hawks Bay or similar model.
The OP also wants to do Grid-Tied which adds further ingredients to the stew.
 
I think the answer will be based on voltage of the 410' run. If (for example) you compare 400v DC with 240v AC, the DC will win. If however you compare 400v DC with 480v AC, the AC will win.....in regards to amps and wire size.

I think it will be easier to deal with higher voltage DC than higher voltage AC. If you purchase an inverter that can take 400v+ DC you can just run 400v to the inverter. If you have go to 480v AC and you don't have a 480v service, then you have to step down to 240v when you get to the service point, which would mean a fairly large transformer and transformer loses.
I do not have a good source for larger wire sizes. From a cost perspective, multiple higher voltage DC runs compared to maybe one very large AC? If that is even possible.
 
that is a complicated question...
you distance from production to house of 410' means you are looking at a wiring path of over 820'!!
Clearly this is the range high voltage as moving current over such a distance would be a real pain in the wallet.

when thinking of high voltage both AC and DC are quite dangerous, however, keep in mind that when "accidents" happen high AC voltage arcs are easier to extinquish, high voltage DC loves to keep that arc going, even after the wire may have melted that arc may continue!

just some quick math to think about:

16kw / 480V = 33amps; even at that very high voltage you have pretty hefty current flowing.
16kw / 240V(rms) = 66amps..no surprise even running a what is normally considered a max house voltage you are moving a lot of current.

820' of wire is really going to cost you and as you increase the voltage demands beyond 480 to 600v you leave the "cheap commodity" wiring and end up having to by more expensive wire (with 800-1000v ratings)...
It is a trade-off on working voltages of everything involved and the larger gauge that would be need to increase allowable current.

thats a long distance to move so much power...unless you are the power company of course hehe
Why do you say "a wiring path over 820'" if the distance is 410'?
 
I'm not a calculator expert but just taking the above 16kw/480v = 33a you could do 2 strings (4 wires) at 17a each down 6awg or 8awg or something mainstream (good price). Even if you get 5% loss in full sun at that level its not the end of the world. In winter its going to be 25-30% of summer.

I have a 13kw PV system with wire runs of 90-120v@45-50a on 6awg going a 150ft. I have an overall system loss of 19% (as far as I can tell) with 16% of it right from the inverters. Maybe 1% with 18650 charge/discharge - so 2% due to wiring/other.

My point is, there are several factors to an overall system and loosing 5% to wiring (there's nothing dangerous if wire is in spec) could be made up by bigger $ on more efficient inverter. Its easy to get OCD on all aspects of solar and after 3 years of operation I've just had to 'let some of it go' and focus on glass 80% full rather than 20% empty.... the clouds pull down production whether I worry about it or not - and they don't even give notice :)
I've never considered allowing more than a 3% voltage drop but now that you say it, it makes sense. I'll have to look into that a little more.
 
I’m using one of these:
Works great, for an output of about 100A DC.
Array operates at about 360vdc.
After the upgrade this Winter, I will have about 9kw of PV.
The array is 250 cable feet from the building where the Schneider inverter in installed.
I ran THHN/THWN #10 AWG, in conduit, voltage loss was minimal.
When pulling the cable through the conduit, I included extra cables, for future growth.
 
I’m using one of these:
Works great, for an output of about 100A DC.
Array operates at about 360vdc.
After the upgrade this Winter, I will have about 9kw of PV.
The array is 250 cable feet from the building where the Schneider inverter in installed.
I ran THHN/THWN #10 AWG, in conduit, voltage loss was minimal.
When pulling the cable through the conduit, I included extra cables, for future growth.
That is substantially overpanelled unless you have more than one CC.
I have a MPPT 100 with 5.7kw total from two arrays which at peak shows 6.3kw.
Specs on the MPPTs are weird. Max output charge current for both models is 80 and 100a, but max output power is 4800 and 6000w for 48 v systems. Those numbers don't jive. My system is more like 53v to 55v and I've seen 103a. Looks like the real limit is the max output power and not the Amp rating.

My arrays are ~120ft from the CC. I used #10 in conduit. Array voltage fluctuates some, but mostly operates at 350-370ish. Open circuit voltage is 450v. I have a combiner at one of the arrays and the CC is wired from that array.
 
Currently panels provide about 5500 watts.
I have also seen 100A going into the batteries @ 53VDC.
The panels I want to add will be facing West, so as to pick up some evening energy, as the light fades from the South facing panels.
 
I'll put this in another light, DC is great but only meant for short distances. Otherwise Edison would have cornered the market and Nikola Tesla would have never invented AC.

You would require a HUGE Copper Cable to carry that amount of DC 500' and I won't even mention EMI/RFI... Goodness Gracious! BTW, DIYsolars guesstimate is LOW, it would require trenching, serious conduits and more.... HINT: I converted Wood Saw Mills to Solar and you wanna see serious DC !

In such instances, the vast majority of people will put together a Powerhouse with Inverter(s) and usually batteries & related and then send AC to home/Shop which can travel great distances with Much Cheaper Thinner Copper.
The historical problem with DC over long distances has been the high cost of converting the Voltage. It's very easy, and relatively cheap, to build AC transformers to convert very high voltage power (best for long-distance transmission) to "intermediate" Voltages (such as 24 kv) for distribution to very small "neighborhood" transformers, providing 120/240 single phase for most home uses over very short distances. If it hadn't been for the inability to "transform" the voltage easily, DC would have won.

AFAIK, the longest point-to-point power line in the USA is high-voltage DC (The Pacific DC Intertie). It runs at +/- 500 kv (1000 kv between two poles, that's definitely HIGH VOLTAGE). The conductors are only 1.6" in diameter (they're steel cored ACSR), and the configuration requires only two conductors. DC is definitely not "meant" for only short distances.
- - - -
So I've argued with your history and labeling of DC as only a short-distance solution. But in THIS vastly smaller configuration, it all depends on the Voltage, and his DC array almost certainly provides power at more than 240 volts (perhaps about 600 volts, if separated into two parallel strings of Series panels). The problem with converting to 240 Volt single phase AC at the Array is the need for bigger wires with more current. Your "create a power house" idea is good, for AC, but requires two transformers: One to BOOST the A/C Voltage far above the 240v which is normally provided by Solar Charge Controllers, and the other to DROP the A/C Voltage back down to 240v at the house. Depending on how high you go between those transformers, you can greatly reduce power loss. But that second transformer is GRID-TIED, with all kinds of ugly equipment qualification and Utility interconnect hassle. And going higher than 600-700V get into very expensive wire.

DC running at only 600 Volts is about 30 amps, with the array properly arranged as parallel groups of serial panels to reach that voltage. I do see a few SCCs which can handle more than 600 volts MPP (while also handling significantly higher disconnect voltage values). Such as this one https://www.ecodirect.com/ProductDetails.asp?ProductCode=Fronius-Primo-15-0-1-TL. And wire rated for higher voltages is very costly as well. But keep in mind that all the Voltage Drop will occur before reaching the SCC, if it's converted at the house. I tossed this into a calculator and got only 3.2% Voltage drop (19.2 Volts lost 581 Volts net) using 8-AWG copper in PVC conduit.

If the utility wouldn't allow that particular SCC (or any other which could handle 600 Volts on the DC side), you could theoretically switch down to 400-480 Volts nominal MPP max and just increase the wire size to AWG-6.

I think that DC long runs, running at high panel voltage to a house-mounted SCC, is the winning configuration in this case.
 
Was just watching the latest installment of @Engineer775 and at 5:00 -> 5:10 in this youtube he says 'SolArk Rule Of Thumb" is to use 8 AWG over 200ft to about 400ft and then transition to #6awg (if you have to). Over the 230ft, they did 8 AWG + a ground. At 8:40 he says it's running 385v on each of the SolArk PV input channels.

He didn't actually say the size of the PV array but from the youtube you can see its substantial and in the relm of the OP's 1st post - e.g. the SolArk 12K can do "PV Power 6500W+6500W = 13,000W" and he shows it producing over 10kw of PV.

This also addresses - is there a unit that takes in 13kw of PV.

@Engineer775 is a real-world, hands on installer and so I think the 6AWG for over 400ft comment in the context of 13kw PV array -> SolArk is legit.
 
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IIUC, the SolArk has two mppt units in it. 6500w each. So you will need to split your array and have two sets of cables running from each half of the array to it's designated mppt.
 
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