10 AWG or 12 AWG from panels to batteries?

[killakitty]

I already had a transfer switch for critical circuits in my house, but I never owned a generator. I bought a pair of Ecoflow Delta Pros with the Dual Voltage Hub and it works great.

Today I caught the sale at SanTan Solar and got a great price on 10 (minimum order) Canadian Solar CS6P-265P. The plan is to use 8, 2 strings of 4 in series, so each string will max at about 1000 watts, 122 volts, 8.6 amps and each set of 4 will charge 1 of the Delta Pros. I'll keep the extra 2 panels in the garage for now as replacements, unless I can figure out how to get them in the limited space I have.

I've got about 100 feet to cover from panels to where I need the MC4's to connect to an MC4 to XT60i cable for the Delta Pros. Those adapters seem to only come in 12 AWG.

Should I buy the 100' of cable in 10 AWG even though the last few feet will be 12 AWG, or should I do the whole thing in 12 AWG?

Thanks!

 

[Watts Happening]

I already had a transfer switch for critical circuits in my house, but I never owned a generator. I bought a pair of Ecoflow Delta Pros with the Dual Voltage Hub and it works great.

Today I caught the sale at SanTan Solar and got a great price on 10 (minimum order) Canadian Solar CS6P-265P. The plan is to use 8, 2 strings of 4 in series, so each string will max at about 1000 watts, 122 volts, 8.6 amps and each set of 4 will charge 1 of the Delta Pros. I'll keep the extra 2 panels in the garage for now as replacements, unless I can figure out how to get them in the limited space I have.

I've got about 100 feet to cover from panels to where I need the MC4's to connect to an MC4 to XT60i cable for the Delta Pros. Those adapters seem to only come in 12 AWG.

Should I buy the 100' of cable in 10 AWG even though the last few feet will be 12 AWG, or should I do the whole thing in 12 AWG?

Thanks!

Let me make sure I’m understanding this correctly, 4 panels in series, then directly to one ecoflow, correct? You are just duplicating this twice.

Or, put another way, you’ll be running (4) wires from the panels to the ecoflow units, correct?

 

[Quattrohead]

12 AWG will be fine but if you want to future proof then you could use 10 AWG. Assuming no permit, correct?

 

[killakitty]

Let me make sure I’m understanding this correctly, 4 panels in series, then directly to one ecoflow, correct? You are just duplicating this twice.

Or, put another way, you’ll be running (4) wires from the panels to the ecoflow units, correct?

Exactly. 4 panels in series, 2 wires in to the house, across the basement ceiling and up in to the garage plugged in to one Delta Pro, then same for the other 4 panels. Outside I'm planning on putting the wire in pvc conduit but it's only about 15' from the panels to where they'll go through the wall.

thanks!

 

[killakitty]

12 AWG will be fine but if you want to future proof then you could use 10 AWG. Assuming no permit, correct?

I mean it's not grid-tied in any way. I'm just throwing 8 used solar panels on my pergola

 

[killakitty]

One last question, and I know there's a lot of info on grounding in the forum, but in the case of this system, 8 panels on a wood pergola, all DC just to charge the Delta Pros, no invertors, not grid-tied etc., should I also run a ground wire from panel to panel, and then through the house and connect it to my grounding rod just outside the garage? Can I put a separate grounding rod out near the pergola just for the panels? Is it possible this is one of those cases where ground is not needed (I want to err on the side of safety here).

Thanks!

 

[zanydroid]

Off grid also needs to be code compliant. You just have a bigger chance of getting away with it.

4s is easily enough DC voltage to be dangerous but I don’t know if that Delta Pro has DC side ground fault detection, so there may not be much you can do about improving the safety of working with those solar panels.

Is there a DC side or AC side grounding terminal in Delta Pro? They would be the natural place to bond your panels.

Is the Delta Pro output going to feed into your house? In that case you should probably bond the panels to house ground but there’s no reason to go all the way back to ground rod. It can go back the same path as your delta pro is feeding, ie into the interlock.

 

[Watts Happening]

I mean it's not grid-tied in any way. I'm just throwing 8 used solar panels on my pergola

Sounds like a small version of my pergola.

I personally ran what I had and that was a set of #10 and a set of #12. Both of my strings run at about 8 amps so I’m well within the ratings of the wire, including derating due to being in conduit.

If you’re going for code compliance all conduit inside the home/structure must be metallic, generally EMT is used. I would suggest running a ground wire to the array, it’s not hard to pull one extra wire when you’re already pulling four. This will save you hassle later down the road.

 

[zanydroid]

I’m not exactly sure what a pergola is but it sounds like one of those open garden structure things. I don’t know at what point a structure transitions from “outdoors” to a structure that requires EMT for solar DC conductors. When it goes into the house, yes. For the pergola I would guess PVC is fine.

 

[killakitty]

Let's see if I can describe this better. The pergola is in the back, southeast corner of my property, all wood, but attached to the house. The panels will go there. I was going to run the 2 sets of 12AWG through PVC conduit about halfway across the house outside, and then through the wall to the inside of the home, where it will go across the basement ceiling (no conduit ok?) and up in to the garage where I have the delta pros, my main service panel, my transfer switch which the delta pros plug in to all at the west end of the house, and then just outside that wall, the west side of the house is the ground rod. So solar cables can run from east to west, first half outside in conduit, 2nd half inside not in conduit, and then plugged in to the delta pros. the delta pros on the west side of the house are plugged in to a transfer switch, next to the main service panel.

The delta pros have a floating ground but that may be AC and not connected to the DC input ports?

If I use grounding lugs on each panel, and run a ground wire along with the 4 solar wires, in pvc conduit outside, then not in conduit inside, and then pop up in to the garage with the solar cables, and connect that to any nearby house ground related to my main service panel or the one in the transfer switch, does that work?

Now, am I directing a lightning strike from outside to inside and is that foolish? Since the solar wire has to travel say 25' outside in conduit, and then about 75' (maybe a bit less) inside the house to the delta pros, is it any less prudent to just bang a grounding rod in to the earth nearby the panels and connect the ground to that, avoiding any situations that would need the ground in the first place travelling through my basement? I know, I'm really getting to the "I'm not an electrician" part of this and appreciate the guidance.

Thanks!

 

[zanydroid]

2nd half inside not in conduit

A circuit's conductors should be presumed to need to by code to be inside a cable assembly or conduit. Same with the EGC (cringely colloquially called ground; called PE elsewhere). There is an explicit exemption allowing the conductors to be separated within solar array.

If you don't want to use conduit you can transition to two 10/3 MC cables however these are required in many cases to be protected by wood from damage when used for solar DC. You can also put your inlet at this location and transition to AC, then you can use a single Romex or whatever.

You should install 4 10AWG for the DC circuits and 1 10 AWG for the EGC, I hope others can chime in on color coding. EGC must be green, DC must not be grey white or green (but beyond that color identification of circuit and polarity is important).

The reason to install #10 is so we don't have to go through the math of confirming the panel output current is low enough for #12. Current panels are always on the cusp of being above or below.

A code compliant install will have EGC go all the way back to where the inverter following the DC circuits.

The delta pros have a floating ground but that may be AC and not connected to the DC input ports?

Can you link the manual?

The delta pro grounds will get grounded and bonded to neutral once you plug into inlet, since inlet has EGC, and the EGC will have path to N-G bond inside the main service panel.

Note that manuals for inverters are notoriously bad at talking about how to wire DC to code. Probably because it's complicated and they don't want the liability.

Regarding grounding at array and lightning protection. The standard thinking on the forum for stationary applications is to use house grounding system. If you get a direct hit, the lightning is not going to care if it fries your house through the EGC or the DC wires. If you get a close indirect hit the secondary ground at the array can collect up the induced voltage in the earth and push it towards the house. My understanding is that the panels in the air are not as good at picking this up.

You can help protect somewhat against indirect hits by adding a SPD (surge protection device) hardwired into the inlet or panel inlet feeds.

Your situation is kind of weird on face value because of backfeeding a house (stationary) from a mobile device. I think it should be treated as stationary. Mobile applications do not use ground rods, I think because it is not practical.

 

[killakitty]

Somewhat fortuitously I guess, the 12 AWG solar wire wouldn't be delivered until late October, so I cancelled and ordered the 10AWG. I'm going to pull a 10AWG solid copper ground along with it. Inside my transfer switch there's a ground and it's even screwed together inside the box for the generator input. Think I can tie the ground in there?

Thanks!

 

[zanydroid]

Might want to consider fine strand THHN for the ground so the bundle moved in a consistent way when you pull.

Yes that ground lug in transfer switch is a good place.

 

[killakitty]

Might want to consider fine strand THHN for the ground so the bundle moved in a consistent way when you pull.

Yes that ground lug in transfer switch is a good place.

All the way from the lug in the garage, through the inside of the house to the outside, and from panel to panel, or do I need to connect it to solid copper for the actual connection to the grounding lugs I intend to use on each panel?

Thanks!

 

[zanydroid]

Solar Panel to Solar Panel should be done with solid #6 since that is the minimum size allowed for exposed run for PV (presumably for resistance against damage, #10 is fine electrically unless there's also a concern about corrosion. #10 also is very rarely used for exposed runs in other parts of NEC so it's probably not a good idea to deviate from the recommendation). The #6 goes into a lay-in weeb lug, there is one designed to dock onto solar panels' grounding screw lugs. I think this is one type (only looked for 5 min, but this site links to some solar panel manufacturer installation notes)

WEEB Grounding Lug 6.7 with 1/4

Wiley Electronics WEEBLug-6.7 Grounding Lug used for grounding anodized aluminum of solar array.

www.altestore.com

You would use a continuous run of #6 that goes through all the solar modules in the array mounted to wood structure.

Note that if you unscrew the weeblug from the solar module, you're supposed to trash that lug and install a new one, since the oxide piercing plate loses efficacy after the first use. So I recommend only unscrewing the #6 retention screw if service is needed, if you have the option. And this probably means you should leave some slack in the #6 run.

Then you transition this to #10 inside a junction box under the array, with the #6 clamped into the junction box with a gland (hard to recommend a size for this, I ended up buying a variety pack with multiple sizes to find the one I liked most).

In the transfer switch there's no need to transition to solid copper unless the connection has trouble with it. The main connection type that has problems as I understand is grounding via a screw, that is cursed. Screw terminals tend to work for both (with a very small minority, like european spec terminals, needing ferrules, and you can ignore this edge case with anything you buy from Home Depot because ferrules are not standard in residential US wiring).

Either way for the #10 part of this, you can use cheap wirenuts to transition to solid so it's not a big deal.

If your question is about more of the macro picture of this install. Not sure how I can explain it properly in text form, I've done it a few times (can't remember if it's on this thread or another one, I'm on a few) and I don't think I'm writing it up very well. Maybe you can start with drawing up one picture for each option and we can iterate on that. It's probably more effective for people following along too if this thread helps htem in the future.