Parts needed for 2 panel array Enphase setup?

erikkiehleerikkiehle Registered Users Posts: 6
Hi all,

I'm wanting to install my own grid-tied solar setup just for fun and educational reasons. I have 2 - 224 watt B grade panels I want to install on top of my cedar patio cover. I have chosen to use 2 Enphase M215 microinverters.

I don't see any point in buying mounting rails. I'm planning to just affix the inverters and panels to the cedar patio cover.

Can I just run the Engage cable to a junction box and run 12-3 or 10-3 NM cable if I run it inside conduit through the eves of the house? Or should I use UF or other type of cable? Wife would like it in conduit for appearances. Would you recommend AC, metallic or non-metallic conduit. I'm thinking I'll only need to run it from the junction with the Engage cable through the house eve. Inside the attic all other house wiring is just running all over.

Will I need equipment grounding? Can I tie that in with the grounding wire running back with the 12-3 or 10-3 cable back to the main panel? Or do I need to plan something else for equipment grounding?

Our electrical supplier requires a disconnect accessible within 3 feet from the service entrance/meter so I'm expecting to run the cable there to a blade disconnect and then to a breaker at the main panel.

Please let me know what I'm missing!

Erik in TX.

Comments

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Parts needed for 2 panel array Enphase setup?

    What you're missing is planning, permits, and permission. You can't just install a grid tie system of any size because you want to; it has to be done legally. That means involvement of the utility and local building authority. For 400 +/- Watts of GTI it probably is not worth the effort.

    They will, however, be able to tell you what is required there for every aspect including the structural mount of the panels & inverters, required wire sizes/types, conduit usage, grounding needs, and breaker sizing for your electrical service. I say "there" because there is not the same as here and even though it ought to be the same code everywhere it isn't.

    If you want to experiment with solar I'd suggest you build a small, stand-alone off-grid system instead. It requires a few more components, but it won't require involvement of inspectors or utilities (at least it shouldn't). You will be able to put together something that will run a dedicated load and get a better idea of how much power you can actually get from the sun under various circumstances (GT systems - the actual power is usually hard to decipher unless you have a good monitoring system).

    Please do not construct an illegal grid-tie system.
  • erikkiehleerikkiehle Registered Users Posts: 6
    Re: Parts needed for 2 panel array Enphase setup?

    Hi, I should have been clear that where I live we have no AHJ for electrical work. There are no permits.

    I've communicated with the utility and their requirements are minimal. The utility will send out an inspector once the system is ready to be energized. That'll be similar to a final inspection you might get from an AHJ before they'll authorize energizing the system. Basically they'll verify I have their required blade-style cut-off available near the meter. Their paperwork isn't even that difficult. They don't require a detailed diagram, just UL certified components. Their permission is readily obtainable.

    Since I don't have a city planning/inspection office to ask these questions of I thought I'd come to this forum.

    I'm familiar enough with the 12v off-grid PV system with inverter for 120v AC on my motorhome. I already purchased these two new 24v 224watt panels originally with the intention of putting them on my RV with a MPPT controller. After honest reflection that we don't dry camp enough to justify the wasted generation of having them on the RV full time I've decided to make them grid-tie.

    I know it's not cost efficient, but I don't care. I want to do it to teach myself how. If this goes well I have plenty of space to expand the array in the future (my key reason for choosing micro inverters, expansion).

    Since I don't have a city AHJ to ask questions of I'd still appreciate thoughts from folks on how YOU'D install an array of two PV panels with Enphase microinverters. This is the planning stage. I'd like info on how to best accomplish my desired array while doing it myself.

    Thanks,
    Erik
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Parts needed for 2 panel array Enphase setup?

    In that case the output from Enphase micro inverters is connected via standard wiring practices. If you're looking at two of them you're looking at 430 Watts maximum (assuming the 215 models) @ 240 Volts or <2 Amps. Pretty easy to handle, unless you're thinking about adding more later. Enphase has an upper limit for their branching of (I think) ten or twelve units - basically a 20 Amp circuit.

    Keep in mind they use some specialized connectors too: http://www.solar-electric.com/enm2somianda.html

    (I must be seeing that page wrong - those prices?)

    If it were me I'd create a dedicated 20 Amp 240 Volt line in the main service panel to connect the micro inverters to. That way you could go up to twelve and not overload it. This would be 12 AWG wire.

    The grounding is a whole 'nother kettle of fish. NEC wants the line run back to the panel and indeed the inverter output ground connection should be. Again standard wiring practice. But by the same token code says the panel frames & mounts should be grounded and that's where engineers start to disagree as how best to. My practice is to run that ground outside the house and down to a grounding rod outside the house to reduce the possibility of introducing high Voltage from nearby lightning strikes to the interior. This is not what code says as they are fixated on the single point ground by shortest route stuff. You won't know which one is right unless something goes wrong, and then if it was right you won't know because nothing will go wrong. Confusing enough? :p

    I expect your utility will be happy providing they see "UL Approved" on the components (no homemade panels) and standard wiring practice on the AC as mentioned above. Use conduit to protect the wiring outside and you can use ordinary 12/2 G safely.

    I'm sure I missed a few dozen points here but someone is bound to point them out.
  • dreesdrees Solar Expert Posts: 481 ✭✭✭
    Re: Parts needed for 2 panel array Enphase setup?

    With the M215 you can have up to 17 inverters per branch circuit. The circuit should be protected by no more than a 20A breaker.

    As 'coot suggests there is more than one way to skin the grounding problem, best practice is to run a separate continuous equipment ground from the equipment to your grounding rod. This ground is separate from the ground on the branch circuit - typically solid 8-6 GA wire run through the panels and inverters, irreversibly spliced to stranded cable if running cable through conduit.

    If you are using EMT, keep in mind that the EMT should also be grounded.

    As far as running conduit back to your main panel or NM/romex wire, obviously if it's outdoors you have to run conduit with individual wires (THWN), otherwise once inside you can use NM wire. From your setup it sounds like you want to do this:

    Branch cable -> junction box outside -> conduit (w/THWN wire inside) running outside to inside -> junction box inside -> NM/romex running to service panel -> 20A dual pole breaker.
  • erikkiehleerikkiehle Registered Users Posts: 6
    Re: Parts needed for 2 panel array Enphase setup?

    Great! Thanks to both of you. Sounds like the rest is pretty basic stuff. I do have 2 questions still.

    1) The utility specifies a lockable blade-type disconnect to be located near the utility service entrance. Would this be an example of such a device? Do only the two hot lines need to be switched? Ground and Neutral can bypass this disconnect and run straight to main panel?
    http://www.solar-electric.com/sqddisw24acn1.html

    2) Is there any free or cheap software to create a simple block diagram for PV location image for the utility?

    Thanks,
    Erik
  • dreesdrees Solar Expert Posts: 481 ✭✭✭
    Re: Parts needed for 2 panel array Enphase setup?
    erikkiehle wrote: »
    1) The utility specifies a lockable blade-type disconnect to be located near the utility service entrance. Would this be an example of such a device? Do only the two hot lines need to be switched? Ground and Neutral can bypass this disconnect and run straight to main panel?
    http://www.solar-electric.com/sqddisw24acn1.html
    Yes, something like that works. HVAC/pool-pump disconnects are also commonly used. The equipment ground can bypass it, but the other ground needs to pass through and ground the switch. The neutral should also pass through. Too bad your utility requires one - all the big utilities in California now no longer require an AC disconnect.
    erikkiehle wrote: »
    2) Is there any free or cheap software to create a simple block diagram for PV location image for the utility?
    You can typically draw them up for one-offs just using power point or similar. If you need a free office suite, look at LibreOffice, specifically the Draw program.
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