Some questions for Microinverter PV System Installation

[Schlag96]

Good afternoon (ladies and?) gentlemen...

I'm a DIY'er and I'm about to pull my permit for a solar install + panel upgrade. Here are the details on my system:

*25 Astronergy 255 watt panels with enphase 215 microinverters
*enphase cables and Iron Ridge XRL rails
*Two 20 AMP AC branch circuits, 10 and 15 panels respectively due to geometries involved)
*Brand new main service panel (200 amp siemens service panel with built in meter socket) in a different location from the old one. The Southern California Edison rep has already come out and marked my new meter location.
*I have submitted my interconnection agreement with line diagram to SCE as well, and have supplied one round of corrections and expect approval any time.

I've done umpteen hours of research and reading but I have a few questions that aren't readily obvious to me thus far.

1. I know I need to have two 8 foot grounding rods at least 6 feet apart... but can I use any existing grounding rod as one of those two, assuming I bond them continuously?

2. I read something about how the equipment grounding wire needs to run in the same conduit as the system wiring when leaving the site of the PV array. So I'll have two branch circuits in insulated 12 AWG and one 6 AWG bare copper wire in my conduit. Does that sound right?

3. SCE does not require a separate disconnect or performance meter, but the sample line diagram does include a solar sub panel. From what I read, I can run my two AC branch circuits directly to the main service panel so there's no reason for a sub panel. Am I wrong?

4. Do the two 20 AMP solar breakers need to be backfed breakers?

5. For normal branch circuits (not the solar ones) requiring GFCI protection, a single GFCI outlet on that circuit is enough right? Or do I need a GFCI breaker on that circuit?

6. I plan on having my enphase cables run into weatherproof J-boxes, then through normal 12 AWG insulated wire to the main service panel. I'll have two circuits (and the EGC 6 AWG bare wire?) running through the same conduit. Conduit and junction boxes will be mounted atop 4x4 treated wood blocks with metal brackets to hold the conduit to the block. So the conduits will be about 4" off the flat composition surface. My wire sizes are good according to the length and temp tables. Any tips/advice for the type of conduit or how I install it?

7. What would be the best way to run all my old wiring over the 30 feet from my old panel location to my new panel location? Would it be worth digging into my walls/roof to run them inside, or can I just run a big conduit / raceway over the roof?

8. Anything else that pops into your mind looking at my plan?

Thanks for reading this far!

I've attached a photo of my old panel for you for comic relief and to marvel at how my house hasn't burned down yet.

Eric
Camarillo, CA

[inetdog]

Good afternoon (ladies and?) gentlemen...

I'm a DIY'er and I'm about to pull my permit for a solar install + panel upgrade. Here are the details on my system:

*25 Astronergy 255 watt panels with enphase 215 microinverters
*enphase cables and Iron Ridge XRL rails
*Two 20 AMP AC branch circuits, 10 and 15 panels respectively due to geometries involved)
*Brand new main service panel (200 amp siemens service panel with built in meter socket) in a different location from the old one. The Southern California Edison rep has already come out and marked my new meter location.
*I have submitted my interconnection agreement with line diagram to SCE as well, and have supplied one round of corrections and expect approval any time.

I've done umpteen hours of research and reading but I have a few questions that aren't readily obvious to me thus far.

1. I know I need to have two 8 foot grounding rods at least 6 feet apart... but can I use any existing grounding rod as one of those two, assuming I bond them continuously?

2. I read something about how the equipment grounding wire needs to run in the same conduit as the system wiring when leaving the site of the PV array. So I'll have two branch circuits in insulated 12 AWG and one 6 AWG bare copper wire in my conduit. Does that sound right?

3. SCE does not require a separate disconnect or performance meter, but the sample line diagram does include a solar sub panel. From what I read, I can run my two AC branch circuits directly to the main service panel so there's no reason for a sub panel. Am I wrong?

4. Do the two 20 AMP solar breakers need to be backfed breakers?

5. For normal branch circuits (not the solar ones) requiring GFCI protection, a single GFCI outlet on that circuit is enough right? Or do I need a GFCI breaker on that circuit?

6. I plan on having my enphase cables run into weatherproof J-boxes, then through normal 12 AWG insulated wire to the main service panel. I'll have two circuits (and the EGC 6 AWG bare wire?) running through the same conduit. Conduit and junction boxes will be mounted atop 4x4 treated wood blocks with metal brackets to hold the conduit to the block. So the conduits will be about 4" off the flat composition surface. My wire sizes are good according to the length and temp tables. Any tips/advice for the type of conduit or how I install it?

7. What would be the best way to run all my old wiring over the 30 feet from my old panel location to my new panel location? Would it be worth digging into my walls/roof to run them inside, or can I just run a big conduit / raceway over the roof?

8. Anything else that pops into your mind looking at my plan?

Thanks for reading this far!

I've attached a photo of my old panel for you for comic relief and to marvel at how my house hasn't burned down yet.

Eric
Camarillo, CA

Whew! That is a lot of questions, some of which are most easily answered if you have a minimum level of understanding already.

And the answer to a question you did not ask:
8. Since your main panel is center fed (as in the main breaker is in the center!) you will not be able to make use of the 120% rule for your backfeed into the panel. You will have to limit the sum of the main and the backfeed to no more than 100% of the bus rating of the panel (which might be the same as the current main breaker size.) If that is the case, you will need to make the main breaker smaller or get a licensed electrician to do what is called a supply side or line side tap into the panel (connecting your PV breaker in a separate panel to the wires on the POCO side of the main breaker.)

7. Do you mean that you are putting in a new main panel, possibly for the above reason? If so any wiring which is on the POCO side of the main breaker (or your PV panel breaker if doing a line side tap) must NOT come inside the walls of the house, period. Certainly not for 30 feet.

6. When you did your temperature calculations, did you include the adder for conduit exposed to the sun above a roof? Not just the higher ambient outside temperature?
PVC can be good for this purpose and is easier to install. Using EMT (thinwall=conduit, as opposed to RMT which is as thick as water pipe) requires a certain amount of skill, and knowledge or experience. But you can also use the EMT itself as the EGC. More about that later. For PVC you may need to use expansion joints.

5. Yes. Making the first receptacle (not outlet) a GFCI will do the job. But new code may require AFCI too and in that case the rules for using an AFCI receptacle instead of an AFCI breaker are more strict.

4. If the breakers are going to be backfed (power input on screws and output on the bus bar) the breakers must NOT have a line or load marking on any of the terminals. There is no specific listing for backfed, as long at the breaker is not marked asymmetrically.

3. See answer number 8. Even a separate sub-panel may not be enough without changing your main panel or doing a line side tap. If a line side tap, then there has to be a breaker or breakers somewhere on the PV AC circuit.

2. And here is where the knowledge is required. Your PV system will require both an EGC (equipment grounding conductor) and a GEC (Ground Electrode Conductor). The EGC does not need to be larger than the other feed wires but the GEC may need to be. If you use the same wire for both you need to follow the GEC requirements, which include that the wire be uninterrupted from each of the microinverter ground terminals all the way to the ground electrode OR be spliced only with an irreversable splice (some crimp type splices and thermal weld splices).

1. Here is where the NEC cycle year becomes important. You may be able to use your existing electrodes for the racking etc, you may be required to install separate electrodes but bond them to the existing ones or you may be required to use new electrodes and NOT bond them. The latter is generally considered now to be a really bad idea but is required by the 2014 NEC.

0. I see that is a Zinsco panel. That is indeed bad news regardless of how good or bad it looks on the surface. You may find yourself installing a new panel as part of this job. Consult a good licensed electrician whose opinion you trust.

[Schlag96]

8. Since your main panel is center fed (as in the main breaker is in the center!) you will not be able to make use of the 120% rule for your backfeed into the panel. You will have to limit the sum of the main and the backfeed to no more than 100% of the bus rating of the panel (which might be the same as the current main breaker size.) If that is the case, you will need to make the main breaker smaller or get a licensed electrician to do what is called a supply side or line side tap into the panel (connecting your PV breaker in a separate panel to the wires on the POCO side of the main breaker.)

Thanks so much for taking the time to reply. I appreciate it.

The pictured panel will no longer exist. I'm putting in a whole new panel, this one:

http://www.homedepot.com/p/Siemens-200-Amp-20-Space-40-Circuit-Overhead-Flush-Meter-Combo-Load-Center-MC2040B1200F/203686447

7. Do you mean that you are putting in a new main panel, possibly for the above reason? If so any wiring which is on the POCO side of the main breaker (or your PV panel breaker if doing a line side tap) must NOT come inside the walls of the house, period. Certainly not for 30 feet.

No I know I need a riser coming in from the overhead. I meant all of the house branch circuits feeding in to the old panel - they all need to get over to the new panel location somehow.

6. When you did your temperature calculations, did you include the adder for conduit exposed to the sun above a roof? Not just the higher ambient outside temperature? PVC can be good for this purpose and is easier to install. Using EMT (thinwall=conduit, as opposed to RMT which is as thick as water pipe) requires a certain amount of skill, and knowledge or experience. But you can also use the EMT itself as the EGC. More about that later. For PVC you may need to use expansion joints.

Thanks, this was the kind of info I was looking for. Yes I did use the tables for hot sun roofs.

5. Yes. Making the first receptacle (not outlet) a GFCI will do the job. But new code may require AFCI too and in that case the rules for using an AFCI receptacle instead of an AFCI breaker are more strict.

OK any of them that need AFCI I'll just do the breakers that way.

4. If the breakers are going to be backfed (power input on screws and output on the bus bar) the breakers must NOT have a line or load marking on any of the terminals. There is no specific listing for backfed, as long at the breaker is not marked asymmetrically.

OK I could have sworn I read something about the breaker going "both ways" but I guess I imagined that.

3. See answer number 8. Even a separate sub-panel may not be enough without changing your main panel or doing a line side tap. If a line side tap, then there has to be a breaker or breakers somewhere on the PV AC circuit.

I should be good with the new panel.

2. And here is where the knowledge is required. Your PV system will require both an EGC (equipment grounding conductor) and a GEC (Ground Electrode Conductor). The EGC does not need to be larger than the other feed wires but the GEC may need to be. If you use the same wire for both you need to follow the GEC requirements, which include that the wire be uninterrupted from each of the microinverter ground terminals all the way to the ground electrode OR be spliced only with an irreversable splice (some crimp type splices and thermal weld splices).

I wasn't planning on using the same wire for both. I was planning on doing the GEC separate, with a 6 AWG copper straight to the earth. I figure if I'm spending $12,000 on a solar system why not give any stray potentials a nice big superhighway to mother Earth

1. Here is where the NEC cycle year becomes important. You may be able to use your existing electrodes for the racking etc, you may be required to install separate electrodes but bond them to the existing ones or you may be required to use new electrodes and NOT bond them. The latter is generally considered now to be a really bad idea but is required by the 2014 NEC.

I'm 2011 NEC with 2013 CA. Yay!

I'm not yet sure how many existing rods I have until I tear into the wall under my old panel.

0. I see that is a Zinsco panel. That is indeed bad news regardless of how good or bad it looks on the surface. You may find yourself installing a new panel as part of this job. Consult a good licensed electrician whose opinion you trust.

Oh I've known since I bought the house last August that I'd be putting in a new panel. The lights dim when you turn on the vacuum! lol

[Mike90250]

Oh I've known since I bought the house last August that I'd be putting in a new panel. The lights dim when you turn on the vacuum! lol

You may look at getting a new Power Company Service Drop installed, if those wires are undersized, the 200' of them, overshadows the 60' in your walls.

[Schlag96]

You may look at getting a new Power Company Service Drop installed, if those wires are undersized, the 200' of them, overshadows the 60' in your walls.

Yep that's in the plan as well. When they move the service they'll make sure what's coming in is correct. All those costs are covered by those little fees I've been paying every month since moving to CA 9 years ago!

How would you guys run all the existing wiring to the new panel?

I'm going to the side wall about 15 feet away. I marked where the main riser will come up with red ink. The way I figure it, I can either:

1. Cut into the interior ceiling and run it all through the joists
2. Cut into the roof and run it all through the joists
3. Run it all up and over the roof through a raceway or multiple conduits

Can you point me toward what you think would be the easiest safest most code compliant way? Or some other option I'm not thinking of?

Thanks!