Solar install turning out really bad - looking for some help/advice please.

[sensij]

You guys are going down the wrong path. With respect to the breaker, 2011 NEC 690.8(A)(3) says:

(3) Inverter Output Circuit Current.
The maximum current shall be the inverter continuous output current rating.

and continues on in 690.8(B)

(B) Ampacity and Overcurrent Device Ratings.
Photo-voltaic system currents shall be considered to be continuous.

(1) Overcurrent Devices.
Overcurrent devices, where required, shall be rated as required by 690.8(B)(1)(a) through (1)(d).
(a) To carry not less than 125 percent of the maximum currents calculated in 690.8(A).

In other words, the number of panels has no effect on the breaker, only the continuous AC rating of the inverter. The SE11400A has a 47.5 A rating, and 125% of that is just under 60 A. Once the breaker is set at 60 A, the wire size follows.

[HX_Guy]

Maybe I should have looked it up before I asked, but found some info online which says:

"In a solar power system, the inverter is responsible for converting a DC electrical current into an AC electrical current, the type of electrical current that normal home appliances use. The AC wattage is figured when you take a solar panel’s listed PTC measurement and multiply it by the inverter efficiency"

The specs on my panel show a PTC of 285W and the inverter has a max efficiency of 98%, so 285 X .98 = 279.3 X 40 panels = 11,172W AC...sound right?

http://www.civicsolar.com/product/canadian-solar-maxpower-cs6x-310p-310w-poly-slvwht-1000v-solar-panel

Going back to your math, 11,172W/240V = 46.55A...with the 80% rule that's 58.19A so the 60A breaker and 6AWG wire is good to go, right?

[HX_Guy]

Thanks Volusiano, the electrical stuff is so over my head, I love when it's explained well like that so thanks for that.

The 12,400 is DC STC (40 x 310w panels). For AC the permit says 11.4kW AC though that seems like the maximum amount, not for my specific system.
I say that because looking at the SolarEdge spec sheet, it shows a max DC STC of 15,350 with a nominal AC output of 11,400.

http://www.solaredge.com/files/pdfs/products/inverters/se-single-phase-us-inverter-datasheet.pdf

Going by what you said, 11.4kw (AC) / 240V = 47.5A...with the 80% rule, that's 59.4A...but again that's the max the inverter will put out if I maxed out the DC input I assume, right?

So how do I figure out the AC system rating for my actual system if the 11.4kW seems to just be something they plugged in from the spec sheet?

[Volusiano]

My permit actually shows #10 ground between the inverter and through the disconnect to the main service panel, though the installer put in #8.
For the hot and natural, he put in #6, though the permit says #4.

There is also a #6 bare ground wire running from the inverter to the existing grounding electrode (but it doesn't pass through any conduit or other meter/disconnect boxes).

My rating is 47.5A for a 12.4kW system going to a 60A breaker.

Although my rating is 46A, multiply by 240V = 11.04KW AC in rating, my system size of 11KW DC STC (44 panels x 250W per panel) is actually only 9.632kw AC. So my rating of 46A @ 240V = 11.04kw AC is probably a little over rated for the actual 9.632kw AC.

Do you know if your 12.4kw system rating is for DC STC, or is that actually 12.4kw AC?

If it's actually 12.4kw AC, then your current is going to be 12.4kw/240V=51.67A. But that's a continuous load which can only be at 80% of wire capacity, so your wire must be 51.67A/0.8=64.6A -> or 4 awg like they spec in the permit. That would also mean that the 60A circuit breaker is not adequate for 12.4kw AC.

BUT if your system rating is 12.4kw DC STC, then your actual system AC rating will be smaller than this. As long as your system's AC rating (not DC rating) is 11.52kw AC or less then you can use 6 awg and 60A breaker).

I also have a #6 bare ground wire from my inverters to the facility ground exposed outside and not in any conduit like yours.

[HX_Guy]

All my hot and neutral wiring in and out of the meter and disconnect box are #6 wires, and the ground is 8 awg. My whole system is rated at 11 KW. If your system is at comparable size, I don't think at that point #10 wire is big enough even for ground. My current rating is 46 A for 11 KW at 240V. It goes to a 60A breaker.

My permit actually shows #10 ground between the inverter and through the disconnect to the main service panel, though the installer put in #8.
For the hot and natural, he put in #6, though the permit says #4.

There is also a #6 bare ground wire running from the inverter to the existing grounding electrode (but it doesn't pass through any conduit or other meter/disconnect boxes).

My rating is 47.5A for a 12.4kW system going to a 60A breaker.

[HX_Guy]

Yeah, wondering that too. The idiot probably had the DVM in resistance mode and popped the meter's fuse.

His voltmeter didn't die..he thought the utility kwh meter died because it wouldn't turn on. Problem was that it wasn't getting power from the disconnect.

[Ben25]

Perfect. Glad it was done right!

[Volusiano]

Also, Volusiano you should not have 8awg wire for a 11kw system. The breaker is sized right, but wire needs to be 6awg.

Ben

Hi Ben, thanks for catching this error. I didn't say it right. What I meant to say was "all my hot and neutral wires are actually 6 awg, and my ground wire is 8 awg". I confirmed this both on my electrical plan and I also went out to verify visually inside the disconnect box. I made correction to the previous post, too. Thanks.

[Ben25]

Also, Volusiano you should not have 8awg wire for a 11kw system. The breaker is sized right, but wire needs to be 6awg.

Ben

[Ben25]

You should be able to attach a box lug to the tub with a green ground screw. They do thread in if you try hard, but I usually tap the hole first to make it easier. Should be at least 8awg ground wire. I'm guessing you have 6awg wire from inverter to point of interconnect?

[Volusiano]

So you're telling me my installer didn't connect something? Nooo! His attention to detail is great! /sarcasm.

Looks like I have to pull the box away from the wall to add the lug? That seems kind of like a pain in the butt, or can the screw just go through from the front side (no nut on the other side?). Do I just connect a #10 ground from the conductor bushing grounding there in the box?

I don't think you need to pull the box out to add the lug nut. On mine, I see they scraped the paint off the inside of the disconnect box where the ground lug is screwed on. I guess to make sure the lug nut makes good electrical contact to the box and not have the paint act as insulation. I'm sure you can use a short self-fastening screw to fasten the lug nut to the box without needing a nut on the other side. I see there are a couple of holes in your disco box. Probably there for the lug nut to get fastened to. I would probably put the lug nut on the lower left hole since that's closer to your ground wires.

Sorry I don't have a pic of mine, but in mine, the ground wire that goes in from the meter to the disconnect box (through the conduit) gets clamped to the ground lug nut that's fastened to the disconnect box. From there a short ground wire is clamped to that lug nut, and from there it goes to lug nut that's tied to the bonding bushing of the conduit that goes out to the main panel, and its other end gets clamped there. The ground wire going out to the main panel through the conduit also gets clamped there. Hope this is clear enough.

All my hot and neutral wiring in and out of the meter and disconnect box are #6 wires, and the ground is 8 awg. My whole system is rated at 11 KW. If your system is at comparable size, I don't think at that point #10 wire is big enough even for ground. My current rating is 46 A for 11 KW at 240V. It goes to a 60A breaker.

[control4userguy]

Wonder how an "open" wiring condition could have killed the installer's voltmeter in the first place? Unless they didn't know how to use it properly and ruined it themselves somehow. Or maybe it was already busted even before that.

Yeah, wondering that too. The idiot probably had the DVM in resistance mode and popped the meter's fuse.

[HX_Guy]

Here is a picture.

So you're telling me my installer didn't connect something? Nooo! His attention to detail is great! /sarcasm.

Looks like I have to pull the box away from the wall to add the lug? That seems kind of like a pain in the butt, or can the screw just go through from the front side (no nut on the other side?). Do I just connect a #10 ground from the conductor bushing grounding there in the box?

[sensij]

There should be a ground lug attached to one of those holes in the back of the disco with the ground wire running to or through it.

Here is a picture.

[Ben25]

There should be a ground lug attached to one of those holes in the back of the disco with the ground wire running to or through it.