• Have you tried out dark mode?! Scroll to the bottom of any page to find a sun or moon icon to turn dark mode on or off!

diy solar

diy solar

Update: 35KW ground mount system added to existing 3kW rooftop solar in Phoenix, AZ.

Would EMT provide enough protection in comparison to RMC or SCH80 PVC?
(E) Severe Physical Damage
RMC shall be permitted to be installed where subject to severe physical damage.

(E) Physical Damage
Steel and stainless steel EMT shall be permitted to be installed where subject to physical damage.


(K) Physical Damage
Where subject to physical damage, Schedule 80 PVC conduit, Schedule 80 PVC elbows, and listed fittings for PVC conduit shall be used.
 
Looks like you are in the mountains, which scratches out the anti-corrosion benefits of PVC over EMT.

I think you are going to combine before you send the circuit down the conduit? There are pros/cons to this. A few large circuits of aluminum would be cheaper and avoid derating issues. However if you ever want to switch to an AC coupled hybrid system, one large 25kW circuit is way bigger than any current inverter can handle (12kW is the biggest people on this forum use). So splitting to 2 or 3 and combining afterward is a bit more future proof.

You can do 3 circuits of #10 before going below 30A on the derating, I think with the AC output rating of your inverters you can even go up to 4 circuits with 70% derate.

You don't necessarily need a line side tap; you can also use something like sum of breakers / combining with your subpanel feeder conductors instead of on a busbar.
 
Looks like you are in the mountains, which scratches out the anti-corrosion benefits of PVC over EMT.

I think you are going to combine before you send the circuit down the conduit? There are pros/cons to this. A few large circuits of aluminum would be cheaper and avoid derating issues. However if you ever want to switch to an AC coupled hybrid system, one large 25kW circuit is way bigger than any current inverter can handle (12kW is the biggest people on this forum use). So splitting to 2 or 3 and combining afterward is a bit more future proof.

You can do 3 circuits of #10 before going below 30A on the derating, I think with the AC output rating of your inverters you can even go up to 4 circuits with 70% derate.

You don't necessarily need a line side tap; you can also use something like sum of breakers / combining with your subpanel feeder conductors instead of on a busbar.
I'm at the base of a mountain in Phoenix, AZ, so yeah, corrosion isn't much of an issue here.

My intent is to combine (5) 30A circuits at the array and make the run to the house with 2/0 to the main service panel. It's about 150ft total. I'm not sure I follow about not using a line-side tap. My main panel in my garage is full so I don't have room for 5 circuits, or 3 for that matter, but also a line side tap would be much easier wiring wise as my 400A panel in the garage would be a pain to get to, whereas that service panel/meter on the east side of the house would be a much easier route to tap into than trying to get to the interior of the garage.

I think then the challenge is where to tap into this monster and run to another disconnect/meter to the left of it.
1722778938717.png
 
My intent is to combine (5) 30A circuits at the array and make the run to the house with 2/0 to the main service panel. It's about 150ft total.

OK, I would recommend double checking how much you want to commit to having a monolithic 150A solar circuit to wrangle in the future. Perhaps you can live with just redoing the 150ft with new wire down the road if this was a mistake or requirements change.

I'm not sure I follow about not using a line-side tap. My main panel in my garage is full so I don't have room for 5 circuits, or 3 for that matter, but also a line side tap would be much easier wiring wise as my 400A panel in the garage would be a pain to get to, whereas that service panel/meter on the east side of the house would be a much easier route to tap into than trying to get to the interior of the garage.
I don't like line side taps because they require more POCO coordination.

BTW I'm using this definition for line side tap, IE governed by 705.11 instead of 705.12.

705.11

(A) Service Connections


An electric power production source shall be permitted to be connected to a service by one of the following methods:
  1. To a new service in accordance with 230.2(A)
  2. To the supply side of the service disconnecting means in accordance with 230.82(6)
  3. To an additional set of service entrance conductors in accordance with 230.40, Exception No. 5

705.12
The output of an interconnected electric power source shall be permitted to be connected to the load side of the service disconnecting means of the other source(s) at any distribution equipment on the premises.


So tapping after the disconnect visible in the picture above would count as a load side tap, and would be top on my list of things to consider/analyze. It may not be easy to outsource to a designer though b/c it deviates from "paint-by-the-numbers" design

Using 705.12(A)


I think then the challenge is where to tap into this monster and run to another disconnect/meter to the left of it.

I think you can squeeze in conduit going above that roof extension and tap into the existing disconnect
 
I'm at the base of a mountain in Phoenix, AZ, so yeah, corrosion isn't much of an issue here.

My intent is to combine (5) 30A circuits at the array and make the run to the house with 2/0 to the main service panel. It's about 150ft total. I'm not sure I follow about not using a line-side tap. My main panel in my garage is full so I don't have room for 5 circuits, or 3 for that matter, but also a line side tap would be much easier wiring wise as my 400A panel in the garage would be a pain to get to, whereas that service panel/meter on the east side of the house would be a much easier route to tap into than trying to get to the interior of the garage.

I think then the challenge is where to tap into this monster and run to another disconnect/meter to the left of it.
View attachment 233874
What's behind the 3 black covers at the bottom?
If breakers, is there a spare? Or space to add another?
If yes to either, this is where I would make the interconnection.
 
Ok, so new twist to this. My utility does not like the idea of two separate solar systems and they need to be combined. I apologize for my newbie question, but how would I go about combining the 2/0awg and 8awg. Would that be another small breaker panel? Are there limitations on the amount of breaker panels? So either I need to go back to the original idea of going to the basement panel with the new array, or run my existing solar system to the far east side of the house and combine them there. I'm just trying to get my head wrapped around this whole thing. If I'm thinking about this correctly, the lines need to be protected, so would that just be a fused disconnect on each line coming in to the house from each solar system?

1722946651360.png
 
Last edited:
A small panel used as a combiner would work. Make sure that it's labeled as such, and I wouldn't put anything else in it.
You might want to check whether your utility has any limitations on connected solar system size.
 
A small panel used as a combiner would work. Make sure that it's labeled as such, and I wouldn't put anything else in it.
You might want to check whether your utility has any limitations on connected solar system size.
Ok thank you. I've been seeing some diagrams where there are many layers deep behind breaker panels. I thought I remember hearing something about limits of disconnects, so that got me thinking if there were limitations of breaker panels.

In regard to the system size, their words were "go as big as you want, we'll update your service to accommodate if necessary". I'm sure there's a limit to that, but they did not have a problem for the 35kW. The basement panel is a 200A panel and has 3/0 SER line feeding it according to the house plans, so that doesn't exceed the feed to that panel.

1722959428841.png
 
would avoid the unsightly SCH80 going along the wall.

An inspector rejected my surface-mount PVC conduit horizontally along the wall.
He said OK only vertically to enter the ground.

If find PVC sunburns, also expands and shrinks as Tim says. Ripped conduit out of a body. You can get slip joints.

I redid that project all in Rigid.
My new project is roof not ground mount, and I'm using EMT.

If you don't have a crawl space the entire length, how about running AC wire in attic?
Put inverter on the wall nearest panels.

Technically, it could be that if PV conduit comes up wall to inverter, then RSD is required. Maybe not? But if so, hanging inverter on a post off of house would avoid that. The only risk to firemen would be DC in the conduit and in the inverter. I would use rigid there, transition to PVC underground if desired.


I agree string not micro inverter, either hybrid or basic grid-tie.

With string, you can parallel two strings of different orientations like SE & SW, less clipping but more hours if over-paneled.


I just figured that since my 35kW would not exceed the 200A rating of that panel in the basement, and that line already has the 200A disconnect near the service panel/meter, it would streamline some of that process.

I'm not sure how all the wires branch out to breaker panels and disconnects.
If PV lands on a 200A panel, 120% rule applies. 200A panel allowed 120% or 240A total breakers feeding it, 200A main breaker + 40A backfed breaker carrying 32A continuous = 7.68kW

Other arrangements would be need to do 35kW, such as smaller main breaker, 225A busbar panel, Line Side Tap, and others.
 
Oh, "Solar Meter" and a disconnect.

No problem to load it up with GT PV.
Is the utility OK with connecting a hybrid, which can draw current in addition to what main panel draws?

I did "load side tap", Meter --> 200A breaker --> Polaris multi-tap (after which I connect breaker panels and disconnect switches to my heart's delight).
That uses feeder tap rules to the things downstream of Polaris.
 
An inspector rejected my surface-mount PVC conduit horizontally along the wall.
He said OK only vertically to enter the ground.

If find PVC sunburns, also expands and shrinks as Tim says. Ripped conduit out of a body. You can get slip joints.

I redid that project all in Rigid.
My new project is roof not ground mount, and I'm using EMT.

If you don't have a crawl space the entire length, how about running AC wire in attic?
Put inverter on the wall nearest panels.

Technically, it could be that if PV conduit comes up wall to inverter, then RSD is required. Maybe not? But if so, hanging inverter on a post off of house would avoid that. The only risk to firemen would be DC in the conduit and in the inverter. I would use rigid there, transition to PVC underground if desired.


I agree string not micro inverter, either hybrid or basic grid-tie.

With string, you can parallel two strings of different orientations like SE & SW, less clipping but more hours if over-paneled.




I'm not sure how all the wires branch out to breaker panels and disconnects.
If PV lands on a 200A panel, 120% rule applies. 200A panel allowed 120% or 240A total breakers feeding it, 200A main breaker + 40A backfed breaker carrying 32A continuous = 7.68kW

Other arrangements would be need to do 35kW, such as smaller main breaker, 225A busbar panel, Line Side Tap, and others.

I can't do a load side tap with that array size, it would have to be a line side tap.

Why is everyone so against microinverters? I could understand the argument of multiple points of failure, but being a ground mount, it's easily accessed and inexpensive to replace the faulty component.
 
Diyer's are mostly of the off grid, self sufficient variety.
Not much use for micro inverters in these scenarios.
Yeah I am not looking to go off-grid. I'm being forced into DIY'ing this because I can't get an installer to work with me since I didn't source my equipment through them. I *might* have found an installer, but they are so slow to reply, it's not giving me much confidence.

I could get a pair of Sol Ark 15k's, but that's about 12 grand vs 5 grand for the microinverters. Since I'm grandfathered into net metering, I don't really need to run batteries, and most inverters nowadays seem to have battery management systems integrated, which is part of that increased cost.
 
Load side tap or whatever it is called, if you had:

Meter
200A main breaker only
200A breaker panel, 125A additional breaker panel, 200A fusible disconnect


That ought to support 40kW PV at 80% of fuse rating.
No wire can get overloaded. The wires do have 400A available to them (200A service disconnect main breaker plus 200A fused PV disconnect), but they are all protected by OCP at far end. Feeder tap rules OK to size wire by far end OCP, no longer than 10' and in metal conduit.


Microinverters are under panels, hot environment, inaccessible for replacement.
If you're going ground-mount, no MLPE required.

Microinverters tend to be sized for one panel, or less than one.
String inverters, you can add panels and strings to over-panel as desired, including multiple orientations for more hours.

String inverters cost less per watt, are more efficient, and I think more reliable.
For 35kW, you could use 7, 5kW, 5, 7kW, 3, 12kW or other combinations giving redundancy.

Prior to the discontinuance of Sunny Boy, I would have used 3, 7.7kW +/- Sunny Boys and 4, 5.75kW Sunny Islands to make a grid-backup system. Then a couple more 7.7kW Sunny Boys on a separate panel for straight grid tie (option to feed into Sunny Island only when off-grid, but too much current to pass through to grid.)

Grid-backup is nice, run A/C and everything when grid is down.
At least one hybrid gives you that.
 
Yeah I am not looking to go off-grid. I'm being forced into DIY'ing this because I can't get an installer to work with me since I didn't source my equipment through them. I *might* have found an installer, but they are so slow to reply, it's not giving me much confidence.

I could get a pair of Sol Ark 15k's, but that's about 12 grand vs 5 grand for the microinverters. Since I'm grandfathered into net metering, I don't really need to run batteries, and most inverters nowadays seem to have battery management systems integrated, which is part of that increased cost.
Nothing wrong with micro inverters, I actually plan to have some in my system.
It's just not the norm around here, in this forum.
 
Why is everyone so against microinverters? I could understand the argument of multiple points of failure, but being a ground mount, it's easily accessed and inexpensive to replace the faulty component.
There are those that get 'religious' over that particular debate. Personally, I suspect the truth is closer to 'it depends'
Shade considerations typically drive discussion of power optimizers or micro-inverters, which don't really apply in your situation.
There are times when the cost of micro-inverters (or power optimizers) is not cost-justified. I've heard others comment that as panel count goes up, the harder it is to justify micro-inverters (with a rough rule-of-thumb in the 10kW system size, but I have no idea how accurate that might be).

Personally, in an urban, roof-mount smaller than 10kW system size, I like the simplicity of lower Amp AC wiring and interconnect for grid-tied (and no house batteries involved). But in your very large ground mount system, I'd be looking for some detailed comparison to see how micro-inverters, power optimizers vs straight string inverter 'pencil out' for your location, system size, and full lifecycle considerations (like future expansion as others have mentioned previously).

As for the reliability of string vs micro-inverters... I've heard people having opposite experience... and the real consideration tends to be long term (system lifecycle) and the latest panel and inverter tech products in common residential usage hasn't been around long enough to reach a definitive conclusion (ie both micro-inverters and string inverters have had recent significant generational changes... so not enough time has passed yet to know if one approach will be 'better' than the other in the long run). Similar goes for current generation hybrid inverters which may (?) end up with life expectancies like hot water heaters (vs old gas dryers that lasted for many decades... at least my families did).
 
FWIW we have PVC conduit in the colorado mountain sun which is very similar to your.. what looks like flagstaff-ish area. After about 15 years it is entirely brown and starts getting micro cracks.
oh it says you're in phoenix though is the sun worse there UV wise or it's just way hotter / slightly less UV?
I'd assume the heat would be worse over the long run for the pvc

1722968981465.png
not in Salida but it is the closest place with data and I'd guess it gets a little less sun than we do, so I think we're nearly identical
1722968998312.png
 
Last edited:
I see what you mean. The problem with that approach is the basement ends right where this red line is. I could bore under the sidewalk still and go into the crawlspace over the downstairs bathroom, and do a loop around into the room. I still would require boring a decent distance, but would avoid the unsightly SCH80 going along the wall.
View attachment 233136

side comment
Trenching under a short section of sidewalk is easy (even for DIY) with the right tools.... though short runs are easier..
of the truly low-tech approach ... I've done the trenching nozzle on the end of garden hose.. worked great... easy to McGuyver a pole to keep hose straight and level...

I've seen later threads about running along wall, which was my first thought...
but *if* you come back to this... instead of the blue line (single larger trench) , I'd argue for 2 separate trenches (1st heading due north under narrow sidewalk, then crossing under sidewalk (door) to get to basement access area where your blue line is) being much easier
 

diy solar

diy solar
Back
Top