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diy solar

Just bought my first off grid house and I’m upgrading the ailing solar. Who wants to get in on the fun?

Apebrains

New Member
Joined
Mar 19, 2024
Messages
25
Location
USA
Hey fellow apes.

Love the self reliance empowerment that goes on here, so I’m picking up my participation.

Last time I posted, I was loading into a solar equipped truck (EcoFlow Delta Pro) to find a house. Fourteen months later, I finally found a paradise in this dismal market that my wife and I could afford.

As one would expect, it needs…a few things.

After living in rolling winter blackouts for the last couple of weeks, we’ve decided to upgrade this:

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To this:

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I’m not a beginner, but I’m no electrician either, so I’d love if you guys could help me learn a few things and answer a few questions, and I’ll try to participate elsewhere with any knowledge I might have.

Probably gonna have a few questions…

Anyone want in on the fun?

-Ape
 
So with the property came 3300 watts of these guys on custom pivot mounts:

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There are ten of them, six on one mount, four on the other.

Here’s the generator left:

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I’m thinking of upgrading the panels at some point, but with the amount of money we’ve just put out, we’re going to have to wait on that leg of the upgrades.

Need to actually insulate the attic first 🙃
 
The 4 panel string is near the minimum voltage the mppt needs, try it and see if it will run.
Generator is 120v so cannot be used as is, chargeverter will fix that.
Update the firmware on the 12000xp to the latest to resolve an mppt startup issue.
Filterguy diagrams are spot on and easy to follow.
 
I agree, except for the unnecessary routing of the PV EGC.
Not that it hurts anything, it's just a waste of effort and copper.
The recommendation is not to ground the PV panels to the inverter ground, keeping it out of the inverter reduces electrical noise transmission into the inverter.
 
can the PV have its own EGC rod ? or is that not recommended to have separate ground rod.
 
if the 4 panel string is too low voltage, connect the 4 and a 6 in series. 10 panels on one mppt, 6 on the other. If that doesn't work, get a small mppt charge controller for the 4 panels direct to battery if that works with the inverter knowing battery current. Or see if two similar voltage & wattage used panels are available locally and add to that mount.
 
can the PV have its own EGC rod ? or is that not recommended to have separate ground rod.
No, the grounding system begins and is created by the N/ G bond.
The grounding system provides a low impedance (resistance) path back to the source for fault current.
Connecting to earth separately, provides zero protection from fault current.
 
Routing the wire directly to where the ground rod is connected is functionally equivalent to landing it in the inverter 99.9%+ of the time.
The remaining 0.01%- of the time are exception cases.

1) Ground fault in the array circuit.
In this case, having the array EGC land in the inverter is probably better because the fault current has a shorter path.

2) Nearby lightning strike.
Ground mount arrays almost always have unintended earth grounding. The OP's rotating mounts are almost certainly earth-grounded through the mechanism and its foundation. In the event of a nearby lightning strike, the array EGC becomes a low-impedance path for a surge from the nearby strike. I would prefer not to put that surge through the inverter, so I recommend the EGC should bypass the inverter.

In both cases, the difference of where the EGC is landed may or may not make a substantial difference.... so you can't say either method is 'wrong'.

@timselectric and I agree on 99.9% of things. On this one, we have different points of view. Unfortunately, that leaves the OP in a place where he has to pick between two different opinions. That is both the curse and the blessing of this forum.

BTW: RF noise is a whole different can of worms. It is nearly impossible to say if landing the array ground in the inverter makes any difference. There are just so many variables that it becomes a case-by-case thing. The one thing that can make a difference is avoiding loops in either the EGC or the Neutral.
 
In both cases, the difference of where the EGC is landed may or may not make a substantial difference.... so you can't say either method is 'wrong'.
We agree that neither option is wrong. They both perform the function intended.
One just takes extra effort and copper.
From a safety standpoint, it's only important that everything is connected to the grounding system. There are many ways to accomplish that. I just always prefer the simplest design. And the manufacturers provide a ground bar with multiple connection points, for this purpose.
 
The 4 panel string is near the minimum voltage the mppt needs,
Let's put some numbers around that.

Inverter Specs:
1736706861742.png

Panel Specs:
1736707017940.png

The key two numbers are the starting voltage of the MPPT (120V) and the Vmp of the Panel (37.7V).

With 4 panels the array Vmp is 4 * 37.7=150.8.

At standard test conditions (STC), the system will work fine. More specifically, at 25C, the system will work fine.

Now we have to explore non STC. If the temperature is lower than 25C the voltage is higher so there is no concern. However as the temperature goes up, there is a concern because the panel voltage can go down. For this we need the Voc temperature coefficient. I found this which indicates a -.31%/degree C.

Next we need to say what the high temperature will be. Lets pick a very high temp: 50C (122F).

50C-25C = 25C|
25C * .31%/C = 7.75%
7.75% * 150.8V = 11.687V
So at 122F, the Array Voc will be 150.8V-11.687=139.11V. This is still above the 120V starting voltage for the MPPT.
 
10 panels on one mppt,
Please do not do that unless you are in a warm climate that never gets cold.
Voc = 45.8V. The array Voc would be 458V and the max voltage allowed on the MPPT is 480V. When you do the math, the system could be damaged if the panels got as 'cold' as 52F (11C).
 
View attachment 269503


I would use one MPPT for each swivel mount as shown above.

The generator does not fit the application very well. It is only ~3000W continuous and it is only 120V. I would recommend using a chargeverter and charging that batteries directly.
Yeah that was the plan, though I’d also like to beef up the input before winter of next year…

And amigo…nothing here fits the application very well. 🥴

I’m working on it. A lot lol
 
The 4 panel string is near the minimum voltage the mppt needs, try it and see if it will run.
Generator is 120v so cannot be used as is, chargeverter will fix that.
Update the firmware on the 12000xp to the latest to resolve an mppt startup issue.
Filterguy diagrams are spot on and easy to follow.
Bingo, agreed on all accounts. Worried about the panels, but we’ll see how we do once I get all of the gear installed to transfer off of the old system. The old system has a well pump attached and some janky interior work…I can’t abide, so I’m fixing everything all at once. It’s got me busy.
 
if the 4 panel string is too low voltage, connect the 4 and a 6 in series. 10 panels on one mppt, 6 on the other. If that doesn't work, get a small mppt charge controller for the 4 panels direct to battery if that works with the inverter knowing battery current. Or see if two similar voltage & wattage used panels are available locally and add to that mount.
I do have a small charge controller that could be used, but maybe I’m misunderstanding, there are only 10 panels total…
 
Routing the wire directly to where the ground rod is connected is functionally equivalent to landing it in the inverter 99.9%+ of the time.
The remaining 0.01%- of the time are exception cases.

1) Ground fault in the array circuit.
In this case, having the array EGC land in the inverter is probably better because the fault current has a shorter path.

2) Nearby lightning strike.
Ground mount arrays almost always have unintended earth grounding. The OP's rotating mounts are almost certainly earth-grounded through the mechanism and its foundation. In the event of a nearby lightning strike, the array EGC becomes a low-impedance path for a surge from the nearby strike. I would prefer not to put that surge through the inverter, so I recommend the EGC should bypass the inverter.

In both cases, the difference of where the EGC is landed may or may not make a substantial difference.... so you can't say either method is 'wrong'.

@timselectric and I agree on 99.9% of things. On this one, we have different points of view. Unfortunately, that leaves the OP in a place where he has to pick between two different opinions. That is both the curse and the blessing of this forum.

BTW: RF noise is a whole different can of worms. It is nearly impossible to say if landing the array ground in the inverter makes any difference. There are just so many variables that it becomes a case-by-case thing. The one thing that can make a difference is avoiding loops in either the EGC or the Neutral.

Yeah, honestly guys, just about anything is an improvement on how things are currently set up. I haven’t yet determined if there is even a functioning ground rod on the property. I did find a ground rod laying next to the fence, which was neither in the ground, nor connected to anything. The property is extraordinarily beautiful, but it does appear that there was some… sufficing going on around here.

The diagram you’ve provided is helpful and along the lines of what I had planned in the first place.

At some point I’d like to try supplementing energy with hydro power in one of my running water bodies as well, but that is a project for later in the year.

I started today just by trying to make space for the units themselves inside the house so that I can eventually demo that waterlogged outbuilding that the setup is currently in.

I’ll then have to move the well pump into the house somewhere as well, and I’m also trying to make sure all of this is up to code lol.

Nobody seems to give rats ass about code out here, but I do in case I want to resell at some stage in the future.

Hoowee. Fun fun!
 
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Please do not do that unless you are in a warm climate that never gets cold.
Voc = 45.8V. The array Voc would be 458V and the max voltage allowed on the MPPT is 480V. When you do the math, the system could be damaged if the panels got as 'cold' as 52F (11C).

Up in the Trinity mountains in Northern California. We get cold and hot, so your temperature heuristic was invaluable.

Next question…where did you guys go to become this literate on the systems engineering front? It drives me insane to not be able to intelligently discuss things with people…..so I need to acquire this level of proficiency lol.

I understand everything you’re saying, but I want to know how it occurred to you to say it 🍻
 

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