DIY Solar Install

[ButchDeal]

Can you put 24 inverters without massive clipping on one MPPT?

I'm getting that data from this datasheet.

try to ask again maybe. why would you have 24 or ANY inverters on an MPPT.
The data sheet is showing that the inverter HAS 3 MPPT inputs. You can use either 1, 2 or 3 of the MPPTs.
The Start voltage for it is 125V.

If you are asking if you can put 24 PV modules on the same MPPT, then sure but they would be a mix of series/parallel to get into the operating range (100-550V) but you would want to mostly be in the RATED MPPT range which is were the inverter is much more efficient most of the time.

[foo1bar]

I've also decided to go with microinverters, instead of optimizers and an inverter. It's actually cheaper and easier.

When I was pricing things, a solaredge system was a cheaper option than an enphase system.
IIRC they were close until you added in the enphase cable, which was a pricy thing.

[Gilligan]

try to ask again maybe. why would you have 24 or ANY inverters on an MPPT.
The data sheet is showing that the inverter HAS 3 MPPT inputs. You can use either 1, 2 or 3 of the MPPTs.
The Start voltage for it is 125V.

If you are asking if you can put 24 PV modules on the same MPPT, then sure but they would be a mix of series/parallel to get into the operating range (100-550V) but you would want to mostly be in the RATED MPPT range which is were the inverter is much more efficient most of the time.

Ok, I think we are going all different directions on this.

I asked about my brother's point of Micro-inverters turning on with almost no sun whereas with a string inverter you don't turn on till it reaches 125v. I was asking if that was correct.

Then someone said "yeah but if you have 24 panels it only needs 4v each", to which I was saying that you don't have 24 panels on one string.

Does all this now make sense? Other than the part where he got snippy in response to someone else's comment like I had said it.

[ButchDeal]

Ok, I think we are going all different directions on this.

I asked about my brother's point of Micro-inverters turning on with almost no sun whereas with a string inverter you don't turn on till it reaches 125v. I was asking if that was correct.

Then someone said "yeah but if you have 24 panels it only needs 4v each", to which I was saying that you don't have 24 panels on one string.

Does all this now make sense? Other than the part where he got snippy in response to someone else's comment like I had said it.

your question stated

Can you put 24 inverters without massive clipping on one MPPT?

from your above comment you meant to ask "Can you put 24 PV modules on one MPPT without massive clipping?"

on a string system the brother is right technically but wrong practically, as a well designed system would easily get to voltage by the time there was enough light to make much difference.

As for the 24 PV modules on a single MPPT sure but not generally in series unless they are low voltage modules. and without clipping sure depends on the size of the inverter and the size of the PV modules though.

[Gilligan]

AHHH, I see... yeah, sorry about that.

My line of thinking is that you want "minimum" number of PV panels per MPPT because you don't want one failed/failing/bird pooped on panel bringing down a whole string of 24 panels right?

[Markyrocks69]

AHHH, I see... yeah, sorry about that.

My line of thinking is that you want "minimum" number of PV panels per MPPT because you don't want one failed/failing/bird pooped on panel bringing down a whole string of 24 panels right?

I was replying to both of you in the same reply.

It's been a long day. But anyways as been said its basically a moot point. I've seen many discussions about the differences between the 2 types of systems and haven't seen anyone discuss this particular issue. The reason being is it is such a fringe inconsequential thing. The majority of the power made is going to be during peak sun hours. Whatever minuscule loss will never make up the difference extra that you pay up front . You'd basically be spending a dollar to recoup a hundredth of a penny a day.

On the note of money be aware that the trunk cable or whatever its called for micro inverters is not cheap. From a 30 second search 300ft is 1000$ which is alot. You might find it cheaper. Edit: to put this in perspective 1000ft of use-2 10 gauge wire is like 350$

also modern panels have a bypass diodes in them that basically shut the panel off if its shaded. Some panels have multiple diodes to shut off quadrants of the panel if parts of it are shaded. So apparently the old wives tale of one panel having bird poop on it tanking a whole string is a thing of the past. Dont ask me how the high efficiency sunpower panels I have work exactly. I have no idea.

[nsgoldberg]

This thread got a little off track....

I'm tired of wading through reviews, spec sheets, and countless forums. I'm just going to pull the trigger on this one. I've spec'd a system that I'm confident I'll be happy with and will last a long time, and be easy to upgrade. I can also install it without derating or upgrading my MSP, since it's 7.6kW. And these panels fit very well on my roof, leaving space for a future solar pool heater (need the pool first, 7-8 years, hopefully), and another 2.5kW of panels when the time comes that I need them.

Please let me know if you see anything glaring that you would change. The price is just under $10k for everything that goes on the roof. Seems like a good price to me.

System Specs:
Panels: 24 Hanwha Q-Cell Duo G5 320W Monocrystalline ($195 ea = $0.61/watt)
Microinverters: 24 Enphase Q7-60-2-US ($112 ea)
Combiner: Enphase X-IQ-AM1-240-2 ($520)
Racking: Ironridge XR100
Also misc hardware, clips, Ironridge Flashfoor
I would only need to purchase the wire, conduit, and flashing to complete the system (Home Depot, est. $600-$1000).

[nsgoldberg]

On the note of money be aware that the trunk cable or whatever its called for micro inverters is not cheap. From a 30 second search 300ft is 1000$ which is alot. You might find it cheaper. Edit: to put this in perspective 1000ft of use-2 10 gauge wire is like 350$

I thought the wire lengths were long enough where you could wire them together using only the panels and the microinverter connections? I will have them on two separate roof planes, so will need 20' or so to connect the two. What cable are you talking about here? That's pretty damn expensive.

Edit: Nevermind, I had 24 of the Enphase Q cables included, at $13 ea. That's $314 for the cables to connect it. Plus a couple of longer lengths for the bridge between roof planes. So $350 or so for the cables. Not too bad, and that's included in the $10k.

[Markyrocks69]

I thought the wire lengths were long enough where you could wire them together using only the panels and the microinverter connections? I will have them on two separate roof planes, so will need 20' or so to connect the two. What cable are you talking about here? That's pretty damn expensive.

The microinverters still need to be wired together using the trunk cable. So basically the trunk cable needs to run through each panel. You could use a junction box to connect one set to the other using regular wire through conduit but I know the trunk cable is some money.

Edit: Nevermind, I had 24 of the Enphase Q cables included, at $13 ea. That's $314 for the cables to connect it. Plus a couple of longer lengths for the bridge between roof planes. So $350 or so for the cables. Not too bad, and that's included in the $10k.

I guess that's not that bad. But again that's compared to a 150ft roll of use-2 10 would probably cost 50$...

This thread got a little off track....

System Specs:
Panels: 24 Hanwha Q-Cell Duo G5 320W Monocrystalline ($195 ea = $0.61/watt)
Microinverters: 24 Enphase Q7-60-2-US ($112 ea)
Combiner: Enphase X-IQ-AM1-240-2 ($520)
Racking: Ironridge XR100
Also misc hardware, clips, Ironridge Flashfoor
I would only need to purchase the wire, conduit, and flashing to complete the system (Home Depot, est. $600-$1000).

How much trunk cable do you need and how much is that going to cost?

[foo1bar]

I asked about my brother's point of Micro-inverters turning on with almost no sun whereas with a string inverter you don't turn on till it reaches 125v. I was asking if that was correct.

To put it simply: It's not correct - definitely not correct for a solaredge optimizer setup. And it's probably also not correct that you get more power out of a microinverter setup for the first 30 minutes of a day compared to a pure string inverter setup. (My guess is that they are within about $1/year worth of power for that part of the day)

[Gilligan]

To put it simply: It's not correct - definitely not correct for a solaredge optimizer setup. And it's probably also not correct that you get more power out of a microinverter setup for the first 30 minutes of a day compared to a pure string inverter setup. (My guess is that they are within about $1/year worth of power for that part of the day)

But I'm talking about a standard string inverter.

Optimizers are a whole other expense I'm not really looking for.

[nsgoldberg]

How much trunk cable do you need and how much is that going to cost?

That would be the $350 I put above. It's not like the older microinverters where you have one main cable and they branch off of it. In the Enphase, you just have short lengths that bridge each junction box. Here's a video showing the install:

https://www.youtube.com/watch?v=rEVgEo4up-I

I'm also looking at roof mounts. Anyone have experience with the Ironridge Knockout Tile Mounts? I like the design, easy to install, it just replaces a tile, no moment arm (the load passes straight to the joist), and built in weatherproofing. They cost almost twice as much as the All Tile Hook, but I think it's a better design, plus no grinding of the backside of the tile. Seems worth the money.

https://www.ironridge.com/pitched-roofs/

[foo1bar]

Edit: Nevermind, I had 24 of the Enphase Q cables included, at $13 ea. That's $314 for the cables to connect it. Plus a couple of longer lengths for the bridge between roof planes. So $350 or so for the cables. Not too bad, and that's included in the $10k.

I would plan out your entire cable path for those cables.
Maybe Enphase has gotten the price down since I looked, but it was definitely more expensive when I looked.
So double check that you have all the cable lengths that you'll need, and that if you need to have cable that is longer that you have the needed plugs to seal the built-in connectors that won't be connected to the enphase microniverters. And I think Enphase encourages you to have their cable come to a spot in the center of the array and from there down to the breakers. ("center-feed"). I think both to minimize losses in the cables and keep the inverters closer to same voltage output. (there's a voltage rise as you go closer to the end of the cable because each micro-inverter is feeding in power. It's like voltage drop calculations you would see for something like an appliance, but in reverse)

[nsgoldberg]

I would plan out your entire cable path for those cables.
Maybe Enphase has gotten the price down since I looked, but it was definitely more expensive when I looked.
So double check that you have all the cable lengths that you'll need, and that if you need to have cable that is longer that you have the needed plugs to seal the built-in connectors that won't be connected to the enphase microniverters. And I think Enphase encourages you to have their cable come to a spot in the center of the array and from there down to the breakers. ("center-feed"). I think both to minimize losses in the cables and keep the inverters closer to same voltage output. (there's a voltage rise as you go closer to the end of the cable because each micro-inverter is feeding in power. It's like voltage drop calculations you would see for something like an appliance, but in reverse)

That makes sense, thanks. I have a location in mind for the combiner, and it will be close to the center of the array. I still need to calculate the exact cable lengths needed and racking lengths. Getting closer now though.

I think my last post was deleted since I had links in it. Does anyone have experience with the Ironridge Kockout Tile System? It seems a lot easier to install, it simply replaces a tile, and has built in waterproofing, plus the load is centered over the lag, so there's no moment arm. Also no grinding of tiles! It's almost twice as much as the All Tile Hook, but I think it might be worth it.

Edit: I found the Quick Mount PV Tile Mount, and like that design better. Plus they sell a tile penetration for conduit which looks really clean.

[Markyrocks69]

Ok so couple things. 1st I'd like to say if you're installing this on a tile roof... be prepared for a nightmare. I'd definitely have a handful of spare tiles available bc if it's real ceramic you're probably going to break a few. That being said how old is your roof? You may have said that b4 idk

2nd I was checking out your shopping list but apparently those micro inverters say that they're meant to work with 60 cell panels. Those q cell duos have 120 cells. Idk if this matters or not but it might be worth looking into if you're going to have a problem or not.

3rd the xr 100 rails dont list your micro inverters as being compatible with their mounting/bonding kit. This is something else you may want to look into. Maybe enphase has their own mounting kit? I have no idea I may be looking at old documentation. But if it's not "listed" and you get a stickler it might not pass.

4th thing. How long do the rails you are using need to be? I only ask bc if you are using 12ft or 14ft sticks, given the wind speed and snow loads in your area, you could probably use the xr10. If I'm correct and you basically get zero snow and low wind speed?