Small home DIY install in Ohio

[foo1bar]

Hello everybody,
...
Hope it will interest you.

Hi Alan. I'm sure it is interesting to some people.
But it's generally considered rude to hijack a thread and post an unrelated topic.
Especially since your post isn't related to the section this thread is in - "Solar panels for your home".
There is an "Introduce yourself" section - https://www.solarpaneltalk.com/forum...ourselves-here
And a section for off-grid: https://www.solarpaneltalk.com/forum...-panel-systems
Both would be better spots.

[SunEagle]

To Alan23

Nice little project with that van. Unfortunately with only 2 x 140watt panels you will only get (at best a couple of hours) 23amp out of them which is no where near enough for a 400Ah battery system.

Now if you used 2 x 6v 230Ah batteries then you have a balanced solar / battery system with 280watts of panels and an MPPT CC.

[Alan23]

Hello everybody,

I support all the ways to use solar energy like Nut&Volts. I've made a DIY electric system on my old (but sweet!) camping car, recycling 2 solar panels from my neighbour's house. They are usual home panels, like this :

dd2649957847232ac33cb5df149acb32631fed08.jpg
(image source : lebonelectricien.pro)

With a few skills, you can create your own electric system. A simple layout looks like this one :

6f3914be1db11f3f655865a4dbcf52ca.jpg

Just make sure to use a MPPT controller if you don't want bad surprises...
Hope it will interest you.

++ Alan

[Nut&Volts]

Thank you guys for the answers! Very helpful information and lets me know I'm headed in the right direction.

I did discover that the AC side of the M190 Enphase cable is not PV cable. It is TC-ER which is exposed run tray cable. Researching now to understand the limitations of this cable.

So the simplest plan right now is to run THHN/THWN-2 cable from my subpanel (through wall and then conduit) all the way to a junction box at the array. If I do anything different it will be best for me to ask my inspection.

[sensij]

Im still curious if anyone has answers to my main questions. Can PV wire be run inside EMT conduit on the roof and into a attic junction box? Is there any type of wire/cable that is allowed on the roof in conduit and inside in the attic and walls?

PV Wire isn't supposed to be in the attic, and the insulation is so thick you fill the EMT fast. THHN/THWN-2 is 90 deg rated wire that is good in conduit both outside and inside. That would be a good choice from your rooftop junction box to your blue box in the attic. I think you can then go to romex from that point to your MSP. Make sure to use the right rooftop temperature adjustments for the wire in the EMT on the roof. I'm not as familiar with grounding for microinverters, but make sure to ground the EMT, if required.

[foo1bar]

Is there any type of wire/cable that is allowed on the roof in conduit and inside in the attic and walls?

I believe wire that is THHN/THWN-2 is allowed in conduit. Both conduit inside and conduit out on the roof.

If you have a box on the roof you could transition to thhn/thwn2 there.
If there isn't an easy way to do that, I would guess that a foot or two of PV wire inside conduit into a junction box in the attic could still pass. (ie. just enough to get to a spot where you can transition)
I think that'd mostly be up to the inspector though.

[Nut&Volts]

Is it really?

I looked at M190's 13 vs. 6+7.
Doing the math I come up with 0.3% less energy (and that's being very pessimistic - ex. assuming that you're at maximum power output all the time you're producing).....

You're right, looking at it more closely it's something like $7 more "profit" a year. Any extra extension cable is at least $20, but that should be my only added costs because my layout can support center or end tap and EMT won't change much. A bit of a toss up it seems, will look closer at my layout to see exact lengths and

Im still curious if anyone has answers to my main questions. Can PV wire be run inside EMT conduit on the roof and into a attic junction box? Is there any type of wire/cable that is allowed on the roof in conduit and inside in the attic and walls?

[tyab]

I center strung my Enphase setup not due to energy loss issues but simply I was doing everything I could to stay under that 2% guidance for total losses from wire resistance to ensure the micros could track the grid as best as possible - and I was getting right up to the limit on my strings furthest away from the combiner sub panel.

For me It meant the following changes:

Upgrading from normal size 2 gauge box to oversized 2 gauge box to meet fill calcs due to oversized downstream wire.
Extra Enphase end terminator per string
Extra Arlington LPCG747 strain relief.

Ran about $20 per string. No change to EMT I was running, no change to wire connectors I was using. For me - worth it since I stayed under that 2%. For someone else - can't say.

[foo1bar]

That's lots of energy over the lifetime of the system going to waste.

Is it really?

I looked at M190's 13 vs. 6+7.
Doing the math I come up with 0.3% less energy (and that's being very pessimistic - ex. assuming that you're at maximum power output all the time you're producing)

So if it's "free" to set it up with a center-tap setup instead of a long enphase cable connected at one end then why not get those very minor gains.
But if it costs more than 0.25% of the system cost then I think it's no longer worthwhile.
If I were looking at it, I'd probably put the decision line even lower - at 0.15% extra cost.

0.15% (or 0.3% or whatever you decide on) doesn't cover a lot - things I think you might have as extra expense:
Extra wire to get to the midpoint.
Extra conduit.
2x the enphase-cable terminations.

I think the main point of that pdf is that you want to avoid too long of strings because the last one on the string could wind up in over-voltage state and shutdown.

[Nut&Volts]

Why are you breaking up the branches? I'm not following the logic that reduces voltage drop. To combine the multiple branches, you can use Midnite Solar's MNPV6-DISCO AC MICRO combiner box to combine up to 3 branches. This will work for you if you just have the 2 branches of 12 and 13. Then exit the combiner box in conduit.

Check out diagrams on page 2-4 on this document. https://enphase.com/sites/default/fi...lculations.pdf
Voltage drop and losses increases exponentially as you get more inverters in a string. That's lots of energy over the lifetime of the system going to waste.

I really want to avoid having extra enclosures/panels in my setup. It's extra time/money/losses that I dont believe is needed. I like solar panels-->inverters-->wire transition-->breaker-->disconnect-->main

[Amy@altE]

Why are you breaking up the branches? I'm not following the logic that reduces voltage drop. To combine the multiple branches, you can use Midnite Solar's MNPV6-DISCO AC MICRO combiner box to combine up to 3 branches. This will work for you if you just have the 2 branches of 12 and 13. Then exit the combiner box in conduit.

[Nut&Volts]

Hey all,
Been away for awhile. Project is still moving forward.

• Roof Inspection Completed - everything is good to go
• M190 inverters purchased - 20 are brand new, so 15yr warranty for only $25
• 245W all black Astronergy panels purchased - pallet of 25 for $0.43/W shipped

I have been able to answer a lot of my own questions, but I'm still struggling with a few on the wiring side. I plan to have two arrays, one of 12 and one of 13 panels. Each one will have two strings of M190s that are btwn 6-7 inverters long to reduce voltage drop. Usually called a center tap I've learned. So this will leave me with 4 interconnect cables which need to go from PV cable to Romex wire (or other house wire).

What I want to do... Run Enphase interconnect cables (PV cable) through wire glands into junction box mount on the end of my rail. From here those same cables will run through EMT conduit (4-6ft) into the siding of a roof gable. This puts the conduit in the attic. I will then the run the PV cable into a standard blue box as a junction box. This is where I will wire nut connect the PV Cable to Romex cable. The Romex cable will run through my attic/down wall into the garage subpanel.

Is that feasible? If I cant run the PV Cable into the attic, can I run the Romex cable in the EMT out to the array mounted junction box??

I understand the AHJ will have final say, but I would like to know if I'm missing something before I ask.
-Kyle

[sensij]

Discovered another issue with SAM and micros. Say I have 10 panels and 10 inverters in my system and two different arrays (so 5 on each). For one it seems like the software only allows you to put arrays in parallel on the DC side. This seems to decrease output.

Microinverter arrays *are* in parallel. Any attempt to treat them as series systems is incorrect, unless you are looking at using something like two 36 cell panels in series to create the equivalent of a 72 cell panel.

[Nut&Volts]

Discovered another issue with SAM and micros. Say I have 10 panels and 10 inverters in my system and two different arrays (so 5 on each). For one it seems like the software only allows you to put arrays in parallel on the DC side. This seems to decrease output. I may just be using this aspect incorrectly. The other issue is that it seems to lump all 10 inverters as one large on instead of applying each on to each panel. This means you'll rarely see clipping when you have arrays in different directions. Makes it difficult to find the reasonable limits for panel sizing

My solution is to simulate with a single panel/micro. I can do for each array layout (ie south roof and then one for west roof). Then just multiple the annual output by the number of panels I plan to have on each array. These results seem to make a lot more sense.

Anyone else experienced this problem? Am I just using the system design functions of SAM wrong?

[Nut&Volts]

Ah. I missed that in the OP first post. Yes I can see the price of a DIY being that low and having a much quicker payback then one for me.

Yes exactly self-install is key here. I also noticed a flaw in my use of the SAM parametric simulation feature (inverter parameters). So my break even is definitely not going to be below 5 years. My cost per watt is nice and lower around $0.7/Wdc (excluding my labor). This is with the old stock M190 inverters, C-grade panels from Sun Elec and Unirac racking. I have an unshaded roof, but have to live with the less sunny weather of Ohio.