Final stages need help

PsychoticEpisode

Solar Addict
So im in the final planing for my system and i have a few more things I need to figure out(All on the AC side only). My RV/cabin will be 100ft from the solar panels as that is the only space I can use for them. My plan is(tell me if there is a better way) is to have my solar shed next to the panels. Inside the shed will be the controller,batteries, and inverter all very close together. Then the inverter will send the AC power 100ft away to the breaker box at the RV(will install the box myself).

When I use this calculator http://wiresizecalculator.net it tells me the only way to get the 15000watts of power I want is to go 240v. As 120v needs 125 amps to carry it and the wire is something called 300 Kcmil(I cant even find this). So if I use 240v how do I wire this and what wire do I buy? The site only tells me I need 1 awg to carry 240v 100ft at 63 amps. Is this all correct? If so what wire will I need to buy? normal welding cable?


Can WIll make a vid on how to wire up the AC side of an inverter?
 

Forbisher

Փփքխմպձժճֆըվմ
So im in the final planing for my system and i have a few more things I need to figure out(All on the AC side only). My RV/cabin will be 100ft from the solar panels as that is the only space I can use for them.
My plan is(tell me if there is a better way) is to have my solar shed next to the panels.
You don't say how many watts of panels but easier to put your solar shed next to your RV
and run the wires from panels 100 feet to the shed.
 

Dzl

Perpetual Newbie & Unofficial Forum Librarian
Staff member
Moderator
When I use this calculator http://wiresizecalculator.net it tells me the only way to get the 15000watts of power I want is to go 240v.

I believe you need and want 240v split phase anyways, this is why in the earlier examples I gave I referenced split phase inverters, or parallel inverters in split phase mode. 50A RV service (which is what you are designing around) is 240V (2 x 120V legs).
https://external-content.duckduckgo.com/iu/?u=https%3A%2F%2Fwww.jaycoowners.com%2Fattachments%2Fimagebucket%2Fimg_338745_2_8c552cc2133e6fb0b87a4dd6e0c1ae95.jpg&f=1&nofb=1



So if I use 240v how do I wire this and what wire do I buy?


Can WIll make a vid on how to wire up the AC side of an inverter?

This is probably not the advice you want, but if you are asking this type of question, or looking for a Will P. intro video on this level of system, and are avoiding 48v DC because of potential risk, I very much think it would be much safer to pay an electrician to do at least the AC side of things.
 

Craig

Watts are Watts!
Staff member
Moderator
I just want to clarify you need 15,000 watts that sounds like a lot at once
 

Hedges

I See Electromagnetic Fields!
So im in the final planing for my system and i have a few more things I need to figure out(All on the AC side only). My RV/cabin will be 100ft from the solar panels as that is the only space I can use for them. My plan is(tell me if there is a better way) is to have my solar shed next to the panels. Inside the shed will be the controller,batteries, and inverter all very close together. Then the inverter will send the AC power 100ft away to the breaker box at the RV(will install the box myself).

When I use this calculator http://wiresizecalculator.net it tells me the only way to get the 15000watts of power I want is to go 240v. As 120v needs 125 amps to carry it and the wire is something called 300 Kcmil(I cant even find this). So if I use 240v how do I wire this and what wire do I buy? The site only tells me I need 1 awg to carry 240v 100ft at 63 amps. Is this all correct? If so what wire will I need to buy? normal welding cable?


Can WIll make a vid on how to wire up the AC side of an inverter?

240V is better, but 15kW at 120V, 125A, just needs 2 awg.
Don't need 1 awg even for 120V. For 240V 63A, I'd use 6 awg.
Just tried the calculator you linked. It defaults to 1% voltage drop. Set that to 5% and try again.
If you had a 15 kW motor with 75 kW starting surge it might be slow to get going, but I think you're just designing for a max 15 kW load, nothing ridiculous.

AC wiring: not welding cable. Could be overhead UF cable, or direct burial UF etc (if allowed), or THHN etc. in plastic or steel conduit.
Our code calls for steel conduit covered 12" with dirt or plastic covered 18"
I've run a bit of 2" steel for AC. Fat wires are hard to pull.
I've run 1 1/4", 1", 3/4" branches for DC. Mostly I pull 12 awg to panels. Lots of it, must have a dozen 500' spools of various colors now.


MBR: Psychotic is setting up 24V batteries. Unless this using the 250 Voc charge controller, AC losses would be lower than DC.

But maybe that's the way to go. voltage drop in DC just slows charging a little, and only at peak sun.
And 7000W of panels at 150 Vmp is less current than 15000W of AC at 120 Vrms.

What I would do (if I was feeling a little psychotic) is this:
1) Use 24V batteries. Two of them. Stick a ground rod in the ground, tie negative terminal of one battery to ground rod, tie positive terminal of other battery to negative terminal of first. You now have +24V and -24V, nothing high enough to scare the missus.

2) Buy two Sunny Island 6048 US. They're about $2200 each on eBay. Wire them in series, 2S1P on the AC side. You now have 120/240V split phase at 13 kW off batteries. Wired to +24V and -24V, inverter gets 48V input. Use fuses on both leads.

3) Buy one Sunny Boy 7.7 kW grid-tie inverter. Configure it for off grid (island) mode. Tied to output of Sunny Island, you can use up to 20 kW when the sun shines, and what you don't use charges batteries.

Don't do this unless you figure out how to use the battery chemistry you want with Sunny Island. I know how to use lead-acid, but somebody else here might know how to use DIY lithium. The supported ones from LG are expensive.
 

Hedges

I See Electromagnetic Fields!
Thank you for all the info so would this be what I need?
With this I can run it from the inverter to the fuse box, then with beakers running to the plugs.

It turns out ampacity ratings for UF cable are based on 60 degree insulation not 90 degree. 6 awg UF gets 55A breaker (not 75A). 4 awg would carry 70A, 1/0 would carry 125A.

Are you setting up 120/240V split phase, so you don't have to carry 125A?

There is another type "USE-2" which is OK for direct burial and rated 90C so smaller gauge could be used.


Alternatively, THHN in conduit



The ground wire can be smaller than current carrying conductors


But again, it seemed like you might do better running wire from PV panels 100' to the charge controller and putting inverter at the load for shorter AC wires. What charge controller do you plan to use? What solar panels, and how many in series?


 

schmism

Solar Addict
120v needs 125 amps to carry it and the wire is something called 300 Kcmil(I cant even find this).

Kcmil or mcm is only found in the utility space. WAY outside the balpark of home game and outside the county for DIY users.

This will give you some info on it if you want to know


from the bottom of that link
MCM means 1000's (M) of (C)ircular (M)ils
kcmil means 1000's (K) of (C)ircular (M)ils
Mil means 1/1000 inch
Circular Mil means the area of a circle 1/1000 inch in diameter
AWG = -4.3125 LN (mm2) + 17.16 (approx interpolated)
AWG = -4.3125 LN (inch2) - 10.74 (approx interpolated)
 

Hedges

I See Electromagnetic Fields!
This is probably not the advice you want, but if you are asking this type of question, or looking for a Will P. intro video on this level of system, and are avoiding 48v DC because of potential risk, I very much think it would be much safer to pay an electrician to do at least the AC side of things.

AC can be turned off, so you aren't handling anything while it is live.

PV panels will always be live, except in total darkness, but MC-4 is touch-safe. You do need to make sure circuit is open before making/breaking connections. Unplug all strings of panels (at both ends) before doing any work on the wire connections to fuses/breakers/charge controllers.

Batteries are always live, also can supply thousands or 10's of thousands of amps. Make sure circuit is open before making/breaking connections. Be careful not to short anything with the wrench (insulated handle is good). Open circuit, maybe then disconnect a cable, before doing any work on connections to inverter or charge controller.

In all these cases, check wires with a volt meter, to each other and to ground, before working.
 

Dzl

Perpetual Newbie & Unofficial Forum Librarian
Staff member
Moderator
Are you setting up 120/240V split phase, so you don't have to carry 125A?

He should be, yes. His goal is to fully power a 50A RV hookup (which is 50A, 120/240 split phase).

@PsychoticEpisode if you go with single phase only (120v), you will be limited to 6000 Watts, not the 12,000W that you want. A 50A RV hookup is two 120V 50A legs (6000W x 2)
 

PsychoticEpisode

Solar Addict
Ok so it looks like everyone is telling me I need to go 240v ac split phase.
Also its better to have the panels 100ft away and not the inverter.
Is this about right?

Thank you guys for the help, once I get the system up and running full ill share pics of it. Ill have it up before the end of the year(unless the world ends before that time).
 

Dzl

Perpetual Newbie & Unofficial Forum Librarian
Staff member
Moderator
Ok so it looks like everyone is telling me I need to go 240v ac split phase.

Correct, by definition you must if your goal is 50A RV service. But also there are many other advantages.

Also its better to have the panels 100ft away and not the inverter.
Is this about right?

I think this is premised on the idea that the PV array voltage would be higher than the AC voltage, and thus voltage drop would be lower. Is this correct folks?

If so, either can be done with an acceptable amount of Vdrop, pros and cons to either approach I think.
 

Hedges

I See Electromagnetic Fields!
Also its better to have the panels 100ft away and not the inverter.
Is this about right?

Probably. (some of mine are.) What charge controller are you using? Which panel and how many in series per string? That determines how much voltage drop.

PV is high current/wattage for a few hours per day. AC drawing from batteries around the clock could be lower current/wattage. It will be on average - 7 kW of PV is 35 kWh/day, can supply 1.5 kW continuous. But instantaneous AC loads could be higher.
We're trying to keep your AC wiring as low resistance as possible to easily start motor loads.
 

Hedges

I See Electromagnetic Fields!
Also its better to have the panels 100ft away and not the inverter.
Is this about right?

Probably. (some of mine are.) What charge controller are you using? Which panel and how many in series per string? That determines how much voltage drop.

My AC house loads are even further, 200'. For now I have 6 awg and 70A breaker. Plan to add a circuit with 2 awg and 100A breaker. This is so I can have smaller loads backed up by battery and other heavy loads powered by grid only. I don't look forward to pulling 2 awg through conduit. 6 awg was difficult enough. I need a tugger!

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There's a trick you can do to avoid pulling wire through conduit:
Lay the wires where you want them. Slip each piece of PVC conduit over the wire, gluing joints as you go. Much easier to get wires through one 10' straight or one 90 degree elbow at a time.

But pulling multiple smaller wires for strings of PV panels is easier: Thread a pulling line as you go (make sure it doesn't get stuck in glue.) Use enough line (or wire if you pull with that) to pull back and pull the next set. Leave the pulling line in the conduit for future use. Even for 12 awg, use stranded wire because it bends easier for the curves. And use wire lube.

PV is high current/wattage for a few hours per day. AC drawing from batteries around the clock could be lower current/wattage. It will be on average - 7 kW of PV is 35 kWh/day, can supply 1.5 kW continuous. But instantaneous AC loads could be higher.
We're trying to keep your AC wiring as low resistance as possible to easily start motor loads.
 
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Forbisher

Փփքխմպձժճֆըվմ
Also its better to have the panels 100ft away and not the inverter.
Is this about right
How cold and hot will it get in the shed 100 feet away from your house?
That's another factor but I suspect your wife may not want batteries, inverters, chargers etc in her house where they would be warmer and cooler than in a shed a safe distance away.
Also nobody knows how many SCCs voltage and amps for your arrays.
 

PsychoticEpisode

Solar Addict
I have the 100a 150v EPever controller with 100w Rich solar panels. Ill be adding 2 more 100a controllers with 370w panels for my next upgrade. I started out with 100w panels so im keeping the first controller on that. From here on out ill only be getting 370-400w panels for the new controllers. They will all feed the same battery bank(LiFePO4) so I can keep adding for a long time.
 
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Hedges

I See Electromagnetic Fields!
I started out with 100w panels so im keeping the first controller on that.

You can mix 'n' match panels on the same MPPT input. So long as the strings add up to similar Vmp, Voc.
After all, the 300 to 500 watt panels aren't made with 12" wafers. Just more cells (of same or similar size) in series. So you get the same with multiple 12V 100W panels in series.

I've got strings of 24, 120W Astropower mono-crystaline, 12, 165W Sharp poly, 8, 327W SunPower mono-crystaline all going to a 1-MPPT input GT inverter. Strings of varying orientation, too.
It only hurts performance when some strings are heavily shaded, then separate MPPT would benefit. But even if one entire string facing West loses direct sun while another facing direct East has sun, not a big penalty. And one panel out of 9 in series shaded (or one diode-bypassed section of one panel in a shorter string) isn't a big deal. Moves a bit off Vmp for some panels, but the power curve is fairly flat around Vmp.
 

PsychoticEpisode

Solar Addict
You can mix 'n' match panels on the same MPPT input. So long as the strings add up to similar Vmp, Voc.
After all, the 300 to 500 watt panels aren't made with 12" wafers. Just more cells (of same or similar size) in series. So you get the same with multiple 12V 100W panels in series.

I've got strings of 24, 120W Astropower mono-crystaline, 12, 165W Sharp poly, 8, 327W SunPower mono-crystaline all going to a 1-MPPT input GT inverter. Strings of varying orientation, too.
It only hurts performance when some strings are heavily shaded, then separate MPPT would benefit. But even if one entire string facing West loses direct sun while another facing direct East has sun, not a big penalty. And one panel out of 9 in series shaded (or one diode-bypassed section of one panel in a shorter string) isn't a big deal. Moves a bit off Vmp for some panels, but the power curve is fairly flat around Vmp.
I know but mixing panels will set off my OCD and ill be frothing at the mouth, so its best to keep them separate.
 
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