More Noob Combiner Box Confusion

[WYtreasure]

Yes, the MPP LV6548 has two controllers built in. It combines them to feed the one battery array. Ideally I'd like to add another battery or two in parallel, but I'll see how this all works first.

The Siemens GF222NA, 2 pole disconnect looks like a great solution, thanks!

I suggest you check the specs on the Siemens before jumping in.
I am still doing some homework but it looks okay for me because of the Class T fuse protecting the disconnect from the battery AND reducing my charge and discharge to about 50 Amps MAX.

https://s3.amazonaws.com/dcc-data-extract/new-delta/asset/Compas/daily/Compas/SpeedFax/SF-17-Sect-04-ALL-web.pdf?04122021

 

[sethile]

I suggest you check the specs on the Siemens before jumping in.
I am still doing some homework but it looks okay for me because of the Class T fuse protecting the disconnect from the battery AND reducing my charge and discharge to about 50 Amps MAX.

I read up as much as I could last night. I found it a bit confusing. I ended up pulling the trigger on the Siemens, along with 2-25A fuses that apparently fit it. I used Amazon Prime so I can easily return them if need be. It seems like it fits the bill, and will certainly be better than most of the other options I was seeing. I'm really surprised with all the solar installations going on there are not more off the shelf solutions for things like combiners and disconnects.

For my installation the Siemens GF222NA is in between the MNPV6 combiner box, and the MPP LV6548 PV inputs. I'm still puzzling out if I need the Class T fuse between the LV6548 and the EG4 battery... The EG4 has a built in breaker, and I'm not seeing anything in the installation instructions about fusing it. I'll run it by Signature Solar... I hate to spend money and add components that are redundant. But I hate fires worse

Working on a block diagram for inside stuff, and updated the PV panel diagram with the new plan. Talked to helpful fellow at the city building department today, and starting plan how to get my application for a permit together. Sounds like they're mostly worried about the roof and wall handling the weight of the panels. Seemed he was very willing to work with me on this.

I clearly have a lot to sort out.... The next step will be contacting MPP to verify it's not a horrible mistake to push they're published 18A PV array input spec on the SCCs to 24.18A in light of them saying not over 25A as reported in the thread above. And depending on how that goes, how best to fuse accordingly.

These are used panels--I'm assuming they will not be reaching their full potential, but...

Edited:
These diagrams are getting pretty close now after verifying with Watts247 on the LV5648, and Signature Solar on the EG4. See next post.




Updated the following diagram after verifying with tech support about the on board 125A breaker being their recommended protection.

 

[sethile]

Nailed some things down today.

E-mail with Watts247:

My question:
Hello,

I picked up the EG4 from the freight terminal yesterday, and it appears to have arrived in good shape. It will be wired to an MPP LV6548 (currently backordered).

Folks on the DIYSolar forum advocate strongly for installing a T-Class fuse. Of course they're also DIYing batteries. I had been thinking the built-in 125 Amp breaker along with the BMS on the EG4 would be adequate protection and I would not need to fuse it.. Thought I'd check in with you on that.

There answer:
Hey Scott,

We do recommend a 125A DC breaker between the batteries and inverter. You are absolutely on the right track keep it up!! If there are any other questions you have please don't hesitate to reach out.

And with Signature Solar:

My question: Hello Folks,

Looking forward to receiving the LV6548 and starting to plan my installation. In light of that I have a pressing question regarding the specs for the PV inputs in the manual, and especially the 18 Amps.

The manual states, " Check the input voltage of PV array modules. This system is applied with two strings of PV array. Please make sure that the maximum current load of each PV input connector is 18A."

There is a discussion about this on the DIYSolar forum in the following thread:
https://diysolarforum.com/threads/mpp-solar-lv6548.14840/page-20

User scottvanv states:
"Ok, definitive answer from Andy Y. with MPP Solar Support Team:

"Please don't worry. PV input current 22A is ok and it will not cause the unit damage. We suggest that please keep the max PV input current within 25A. Thank you."
Do you think I'm OK going with the 25Amps mentioned here? I'm bumping up against the 25A with my current plan:


These are used panels--I think it's unlikely they will be achieving specs. I have 26 of them to work with:
Specs:
Model: SS250P-60
Maximum Power: 250W
Open Circuit Voltage: 37.6 Voc
Voltage at Pmax: 30.3 VPmax
Short Circuit Current: 8.85A
Current @ Pmax: 8.27A
Max System Voltage: 600V
Fuse rating: 15A
Dimensions: 39" wide x 65" tall
Weight: 42 lbs

Another option would be to stick with 2 parallel strings and run 6S2P into each controller. It would be more challenging logistically with my available locations, but doable. The Voc of 6 in series would be 225.6 Voc. It does get cold here in Western KY, but not often. We had a cold sunny morning yesterday (lows in the teens). Neither location receives full sun in the winter until mid-morning.

Seems like I'm bumping up against Volts to use 24 panels in 6S2P into each input, or Amps for 25 panels with 5S3P for one of them and 5S2P for the other. I'd hate to drop it down to 5S2P for each input and only use 20 panels. But I also hate blowing things up...

What do you think?

Their answer:
Scott, the unit will self regulate, along as you dont go over voltage.

Over paneling by up to 20% is fine, it won't do any harm

Ian

So, I'm feeling pretty good about the basic plan so far... still working on the loose ends and waiting for stuff to show up. But I think I have enough to go ahead with preparing my building permit application.

Thanks for all the help!

 

[Supervstech]

With 6 in series and a max low temp of -18C
The max voltage produced would be 242.6V

 

[sethile]

With 6 in series and a max low temp of -18C
The max voltage produced would be 242.6V

Thanks for this! I was wondering how the numbers worked out, but had not found the equation and run the math yet. I was planning to do that if having three string in parallel was nixed by tech support.

My best sun is on the South facing wall, which has room for 10 panels max, so having 5S2P there maximizes that area (I don't want to split a series string between the South wall, and the East facing roof--that seems like a quick way to degrade the potential with shading and orientation differences within the string. So 10 on the side leaves me with 16 panels for the East facing roof (assuming they are all good--they're used after all). 5S3P uses more panels than I can do with 6 in series without buying more panels. And if I bought 2 more panels and ran 6S3P up there, I'd be over paneling by 500 watts (still within the tech advice of getting away with 20% over, by 300 watts, but pushing on it).

With clearance on the 5S3P from tech support, I fell like its my best option.... It maximizes my best sun, eliminates breaking a series string up into different orientations, and uses all but 1 of the panels I have, which I can almost certainly use for something else at some point

 

[WYtreasure]

Thanks for this! I was wondering how the numbers worked out, but had not found the equation and run the math yet. I was planning to do that if having three string in parallel was nixed by tech support.

My best sun is on the South facing wall, which has room for 10 panels max, so having 5S2P there maximizes that area (I don't want to split a series string between the South wall, and the East facing roof--that seems like a quick way to degrade the potential with shading and orientation differences within the string. So 10 on the side leaves me with 16 panels for the East facing roof (assuming they are all good--they're used after all). 5S3P uses more panels than I can do with 6 in series without buying more panels. And if I bought 2 more panels and ran 6S3P up there, I'd be over paneling by 500 watts (still within the tech advice of getting away with 20% over, by 300 watts, but pushing on it).

With clearance on the 5S3P from tech support, I fell like its my best option.... It maximizes my best sun, eliminates breaking a series string up into different orientations, and uses all but 1 of the panels I have, which I can almost certainly use for something else at some point

MidNite Solar - Classic Sizing Tool.

MidNite Solar is the industry leader and manufacture of quality Renewable Energy System electrical components and E-Panels.

www.midnitesolar.com

Check with the National Weather Service for the coldest recorded temp in your area. You may be surprised.

This might be a good time to test the panels, one by one. Wear rubber gloves ?

 

[sethile]

This might be a good time to test the panels, one by one. Wear rubber gloves ?

I looked at 2 of them the other day, which looked pretty good for late afternoon direct sun. I do plan to test them all, after I get the gloves

MidNite Solar - Classic Sizing Tool.

MidNite Solar is the industry leader and manufacture of quality Renewable Energy System electrical components and E-Panels.

www.midnitesolar.com

Check with the National Weather Service for the coldest recorded temp in your area. You may be surprised.

This might be a good time to test the panels, one by one. Wear rubber gloves ?

That's a fantastic tool, thanks! And I did check the weather service, and you're right, I was very surprised! -20F!

This is our 27th winter here, and I think we've been just under 0F maybe 3 or 4 times at the most, and just briefly... Running that nifty calculator with 0 puts max Voc at 257.4--even that is too high! -20 put me well over at 265.8 Voc. Guess it only takes one time to fry the SCC or something else.

Safer than 6 in series using the information from tech support specifically giving me the green light on the 5S3P at 24.8Amps, while also saying the unit self regulates as long as you're not over voltage. Also, the 5 in series works better for my locations, uses more panels in even strings, and with less in series I reduce the shading issue. Win Win Win, assuming I don't screw it up

 

[WYtreasure]

I looked at 2 of them the other day, which looked pretty good for late afternoon direct sun. I do plan to test them all, after I get the gloves

That's a fantastic tool, thanks! And I did check the weather service, and you're right, I was very surprised! -20F!

This is our 27th winter here, and I think we've been just under 0F maybe 3 or 4 times at the most, and just briefly... Running that nifty calculator with 0 puts max Voc at 257.4--even that is too high! -20 put me well over at 265.8 Voc. Guess it only takes one time to fry the SCC or something else.

wOw -20 is surprising me as well. ?

Someone smarter than me knows how to insert a disconnect which is temperature controlled. We just have to find that someone.

 

[sethile]

wOw -20 is surprising me as well. ?

Someone smarter than me knows how to insert a disconnect which is temperature controlled. We just have to find that someone.

Oh, of course! That makes a ton of sense... Bet it would be an interesting project, too, but can only imagine the struggle sourcing the right components to pull it off, even if I found the right Brainiac to help

I bet eventually there will be off the shelf solutions for all this stuff scaled to a variety of installations. It surprises me they're not already out there! Maybe I'm just not finding them... I've seen some cool things for big $$ grid tie systems, but as soon as I back down into an appropriate spec for my little 6.5KW installation, it's slim picking...

As it stands I'm better of pushing Amps with the 5S3P and letting the LV6548 do it's "self regulate" trick if and when it needs to.

 

[WYtreasure]

I have a manual disconnect (in the nice warm house) between the combiner box and the charge controller.
I realize "manually disconnecting" is not a popular option around here but it could be used during those times of SUPER COLD TEMPS.

If you are headed for temps below ZERO or have THUNDERSTORMS approaching, perhaps you could just disconnect until the hazard passes.

Down the road when Mr. Wizard invents the automatic disconnect doohicky you can stop babysitting the system. I'm home a lot and babysit mine.

 

[newbostonconst]

I have a manual disconnect (in the nice warm house) between the combiner box and the charge controller.
I realize "manually disconnecting" is not a popular option around here but it could be used during those times of SUPER COLD TEMPS.

If you are headed for temps below ZERO or have THUNDERSTORMS approaching, perhaps you could just disconnect until the hazard passes.

Down the road when Mr. Wizard invents the automatic disconnect doohicky you can stop babysitting the system. I'm home a lot and babysit mine.

I wouldn't do that....in my opinion the damage is done on reconnection. My SCC starts making power on the cold days before the sun is fully up so they never get to high even though my system is designed to be high on the cold days.

 

[WYtreasure]

I wouldn't do that....in my opinion the damage is done on reconnection. My SCC starts making power on the cold days before the sun is fully up so they never get to high even though my system is designed to be high on the cold days.

Interesting, I'm listening and am pretty sure the OP wants to hear more as well.

 

[newbostonconst]

Interesting, I'm listening and am pretty sure the OP wants to hear more as well.

Ok, I am not an expert but my other thoughts on this are that on those cold days the panels aren't aimed directly at the sun so high voltage is even less likely to happen....

I think the calculator is set to reject for worse case, like if they were aimed directly at the sun at high noon and powered them up on the coldest day... Then the scc would fail.... The likely hood of that is near zero if you understood the concept...but that is my guess....

The other to fail would be just pushing to many watts through it so.... I would like add another set to my string if I could find matching panels....also thought about putting some west facing and east facing on the same scc with blocking diodes.... Then I could use the same 250 foot cable and combiner box and scc but with more panels...

I do like testing things and again am not an expert....I have my hybrid inverter running on 20 cells in series right now at 69 volts which isn't common... 550 ah's... Pack made of 20-280 ah cells, 4-55 ah cells and two Battleborn cells in a series/parallel configuration...

 

[WYtreasure]

Ok, I am not an expert but my other thoughts on this are that on those cold days the panels aren't aimed directly at the sun so high voltage is even less likely to happen....

I think the calculator is set to reject for worse case, like if they were aimed directly at the sun at high noon and powered them up on the coldest day... Then the scc would fail.... The likely hood of that is near zero if you understood the concept...but that is my guess....

I have come to understand the highest volts come when there is little to no sun, so no current, and extremely cold temperatures. For some reason the panels produce voltage when subjected to extreme cold. There are numerous discussions on the subject within the forum but I am a failure at finding things here.

Protecting my equipment from known hazards is my motivation for utilizing a manual disconnect. When the thunderstorms are coming I can pull a lever and maybe keep the lightning away from the controller and everything downstream of it.

I understand that overpaneling, done properly can be a good thing, some panels facing East, some facing West and you get the best of both worlds without frying the Controller. I honestly do know everything about nuthin.

 

[Supervstech]

wOw -20 is surprising me as well. ?

Someone smarter than me knows how to insert a disconnect which is temperature controlled. We just have to find that someone.

A simple low temp charging disconnect could be configured to drop solar input below -5F common battery protect setup.
There is YouTube videos on the subject using a dc relay. Here’s one, but I don’t like the relay he uses… get one rated for the voltage of the array.

 

[sethile]

A simple low temp charging disconnect could be configured to drop solar input below -5F common battery protect setup.
There is YouTube videos on the subject using a dc relay. Here’s one, but I don’t like the relay he uses… get one rated for the voltage of the array.

Great idea!! If I end up pushing it I'll look into doing that.

On a related question: I'm more worried about power output (amps and watts). My planned configuration of 5S3P array is safe in terms of Voc even at -20 F. But I'm on the edge the max for current (18A in the specs, and 25A from tech folks, and my array is 24.81A without the coefficient). And I'm pushing it on the Watts (4KW in the specs, and my 5S3P would be 3,750W without the coefficient).

Tech support said it's safe to over panel--apparently the LV5648 will self regulate as long as I don't go over 250Vs, so I should be fine. But I'd like to check what might happen. Neither power or current was shown on the tool for the low temperature coefficient (or maybe I missed it). Can you point to an equation or a tool that would include Watts, and/or current? If the results are alarming, it might be fun and fruitful to play with the low temp shutoff relay like batteries use.

 

[newbostonconst]

I have come to understand the highest volts come when there is little to no sun, so no current, and extremely cold temperatures. For some reason the panels produce voltage when subjected to extreme cold. There are numerous discussions on the subject within the forum but I am a failure at finding things here.

Protecting my equipment from known hazards is my motivation for utilizing a manual disconnect. When the thunderstorms are coming I can pull a lever and maybe keep the lightning away from the controller and everything downstream of it.

I understand that overpaneling, done properly can be a good thing, some panels facing East, some facing West and you get the best of both worlds without frying the Controller. I honestly do know everything about nuthin.

I have a MidNite SCC and have been watching it at sunrise and with my configuration it has been in MPPT charging mode when the sun is barely up. I never see a high voltage increase...

 

[newbostonconst]

A simple low temp charging disconnect could be configured to drop solar input below -5F common battery protect setup.
There is YouTube videos on the subject using a dc relay. Here’s one, but I don’t like the relay he uses… get one rated for the voltage of the array.

Isn't that pretty much what the HyperVOC is on the MidNite charge controllers?

 

[Koldsimer]

Isn't that pretty much what the HyperVOC is on the MidNite charge controllers?

Exactly. It provides an additional buffer for your scc to prevent it from frying itself in an over voltage situation. I run a 48v batttery and a classic 150 so it will protect itself up to 198v.

 

[sethile]

Update: The MNPV6 will not work for my set up. This is entirely my fault. It's clear in the specs:

Applications:  PV combiner up to six strings using MNEPV breakers rated for 150VDC. 120 amps total output  PV combiner up to three strings using MNEPV breakers rated for 300VDC. 120 amps total output  PV combiner up to four strings using 600VDC fuses and MNTS touch safe fuse holders rated for 600VDC  DC load center using MNPV breakers

My 5 series strings are 188Voc ea. I couldn't figure out why the 250VDC breakers I ordered would not fit. Well, that's why... I could likely fit 4 of them using the setup for the fuse holders, but it's time to bail. I either need two combiner boxes (one for 5S2P, and the other for 5S3P), for each input on the LV5648, or I go with branch connectors and in-line fuses (I'm back to leaning that direction).

In addition to this rather discouraging revelation about the MNPC6 for my set up, another big surprise occurred when I opened the boxes from Renogy. Instead of the 5 breakers I ordered, I received 5 CASES (12 breakers in each case for a total of 60)!!! Some poor soul in shipping is likely getting admonished if not canned for that one!

It's sad to be honest some days... Instead of listing all these breakers on eBay I'm working on RMAs for the entire mess.... Tech support did thank me for letting them know