MNDC250PLUS wiring question (see pic)

[Jacotenente]

Working on my system rewire. Using #4 THHN and #6 THHN (for the solar side). In this picture, I landed the #4 THHN up to the big 250a breaker on the LINE side (which will go down to the batteries). LOAD on that breaker will go to the inverter (with 4/0 cable). How does this look? The output of the three Classics (max) will be about 130 amps spread out over three feeds, tied into that LINE side of the 250a breaker and then fed down to the batteries with the 4/0.

Secondly, for the PV input side (where current is lower, voltage is higher)...gonna use a NEG bussbar for all three arrays PV NEG. Then feed three the Classics NEG PV input from that single bussbar. Is that correct?

Never wired up one of these. Not installing the shunt.WB-Jr inside this box.

Thanks.

Chris

[Robin]

I still do not understand this wiring? I see three C series breakers all feeding the top side of a 250 amp breaker. It appears you also intend to use the same 250 amp breaker to feed an inverter. Why would you want to go through two breakers for each Classic feed? I am assuming the three breakers are the battery breakers from three Classics?
Can you draw out a wiring diagram and attach that? It would simplify things for analysis.
Thanks,
Robin

[Jacotenente]

Thanks. I can "try" to draw up something. Yes, the three bottom breakers are for the Classics. The LINE feed for those three and the 250a breaker will have a 4/0 cable direct feed to the breakers from the battery bank. Electrically, they are isolated. The LOAD on the 250a breaker will be isolated down to the inverter by the 250a breaker with a 4/0 cable.

Or, think of it this way, the top of the 250a breaker will serve as a bussbar LINE direct to the battery bank.

Chris

[Jacotenente]

See picture...not a wiring diagram, but serves to better explain why I am wiring it this way. Unless I am way-wrong. The current coming out of the three small breakers (total) can reach 140 amps (ish) during ideal sun conditions. I also included an "overall" picture of where I stopped. The solar wires are hanging off to the side. Can the NEGs be bussed together?

Chris

[dgd]

A few suggestions...
You could wire the 3 breakers to the bottom post of the 250A breaker and use a single short piece of #4. Then common the C breaker top posts together using a section of copper bar with holes drilled ( or use a piece of flattened copper pipe)
There is enough room to fit a shunt +WBjr and a short bolt type bus connector (brass or copper type). Then you can use ring lug terminated copper cables for the inverter and three Classic -ve lines. Another short section of copper bar to connect to the shunt, the other side is the 4/0 main battery cable.
dgd

[dgd]

As a final safety I'd suggest near the battery where your 4/0 positive connects insert a T class 400A fuse.
dgd

[ClassicCrazy]

yeah - like dgd says - I don't get why you don't bring battery positive to bottom of big 250 amp  breaker and then the inverter cable goes to top post of that 250 amp breaker.  That is how Midnite  schematic shows to do it  too.


Larry

[Jacotenente]

A few suggestions...
You could wire the 3 breakers to the bottom post of the 250A breaker and use a single short piece of #4. Then common the C breaker top posts together using a section of copper bar with holes drilled ( or use a piece of flattened copper pipe)
There is enough room to fit a shunt +WBjr and a short bolt type bus connector (brass or copper type). Then you can use ring lug terminated copper cables for the inverter and three Classic -ve lines. Another short section of copper bar to connect to the shunt, the other side is the 4/0 main battery cable.
dgd

Thanks. I thought of doing that (single piece of copper) and #4 wire it up to the 250a breaker. I know it is a short run for the total amount of current the three Classics would put out...#4 THHN is rated for what amount of amps? 90 amps? ALSO, that is the battery side. Per the picture I posted, on polarized DC circuit breakers...that goes to the LINE side. Or are all the videos, literature, and questions I have researched incorrect? These breakers are labeled as such. Thanks!

Chris

[Jacotenente]

yeah - like dgd says - I don't get why you don't bring battery positive to bottom of big 250 amp  breaker and then the inverter cable goes to top post of that 250 amp breaker.  That is how Midnite  schematic shows to do it  too.


Larry

I attached a picture of what doesn't make sense concerning LINE/LOAD side of polarized DC breakers. Additionally, (following DC breaker LINE/LOAD wiring), the PV + Disconnect is shown backwards too (assuming LINE is on top and LOAD is on the bottom of the breaker). Now (look at second picture), if ALL breakers had their LINE/LOAD labeled the same way then the schematic would be more correct. However, they are not. On the second picture, the ++ on this breaker is the LINE side (per what Ryan said on the video...that goes to the side with the greatest potential...ie, the PV array or battery). And, NO, my breakers are NOT mounted upside down.

Here is a link to Ryan's video explaining DC breakers (start watching at 4:40)
https://www.youtube.com/watch?v=Mtq3cs9Gucc

[ClassicCrazy]

yeah - like dgd says - I don't get why you don't bring battery positive to bottom of big 250 amp  breaker and then the inverter cable goes to top post of that 250 amp breaker.  That is how Midnite  schematic shows to do it  too.


Larry

I attached a picture of what doesn't make sense concerning LINE/LOAD side of polarized DC breakers. Additionally, (following DC breaker LINE/LOAD wiring), the PV + Disconnect is shown backwards too (assuming LINE is on top and LOAD is on the bottom of the breaker). Now (look at second picture), if ALL breakers had their LINE/LOAD labeled the same way then the schematic would be more correct. However, they are not. On the second picture, the ++ on this breaker is the LINE side (per what Ryan said on the video...that goes to the side with the greatest potential...ie, the PV array or battery). And, NO, my breakers are NOT mounted upside down.

Here is a link to Ryan's video explaining DC breakers (start watching at 4:40)
https://www.youtube.com/watch?v=Mtq3cs9Gucc

Okay  Chris - I have a couple breakers here and I see what you mean with the line and load labels. On the smaller DIN rail mounts they have the + on the bottom which would be coming from the source voltage. But as you say the other panel type breaker with studs  is labeled Line on the top and Load on bottom .Guess I never paid attention to those.

I just looked this up and found discussion about this  in the past.
The small Din Rail mount breakers that have the + at the bottom need to be connected to with + to higher voltage source.
The other panel type breakers with studs are not polarity sensitive and you can wire them either way .
Discussion was here
http://midniteftp.com/forum/index.php?topic=3538.msg34227#msg34227

And this is good since I wired my system with panel stud breakers with source voltage at the bottom !  Plus that is the way Midnite shows them wired in photo's of their wiring too.

Larry

[Jacotenente]

yeah - like dgd says - I don't get why you don't bring battery positive to bottom of big 250 amp  breaker and then the inverter cable goes to top post of that 250 amp breaker.  That is how Midnite  schematic shows to do it  too.


Larry

I attached a picture of what doesn't make sense concerning LINE/LOAD side of polarized DC breakers. Additionally, (following DC breaker LINE/LOAD wiring), the PV + Disconnect is shown backwards too (assuming LINE is on top and LOAD is on the bottom of the breaker). Now (look at second picture), if ALL breakers had their LINE/LOAD labeled the same way then the schematic would be more correct. However, they are not. On the second picture, the ++ on this breaker is the LINE side (per what Ryan said on the video...that goes to the side with the greatest potential...ie, the PV array or battery). And, NO, my breakers are NOT mounted upside down.

Here is a link to Ryan's video explaining DC breakers (start watching at 4:40)
https://www.youtube.com/watch?v=Mtq3cs9Gucc

Okay  Chris - I have a couple breakers here and I see what you mean with the line and load labels. On the smaller DIN rail mounts they have the + on the bottom which would be coming from the source voltage. But as you say the other panel type breaker with studs  is labeled Line on the top and Load on bottom .Guess I never paid attention to those.

I just looked this up and found discussion about this  in the past.
The small Din Rail mount breakers that have the + at the bottom need to be connected to with + to higher voltage source.
The other panel type breakers with studs are not polarity sensitive and you can wire them either way .
Discussion was here
http://midniteftp.com/forum/index.php?topic=3538.msg34227#msg34227

And this is good since I wired my system with panel stud breakers with source voltage at the bottom !  Plus that is the way Midnite shows them wired in photo's of their wiring too.

Larry

Thanks. Two questions:
1) If the C-series (studded) DC breakers are "not polarity sensitive" as you say, WHY are they labeled with LINE and LOAD?
2) Concerning the large 250a breaker...mine is labeled "LINE and LOAD". Is it polarized? If so, LOAD is on the bottom and should go to the inverter...not to the batteries (the Midnite Solar wiring diagram/pictures show THAT is where you put the battery cable on). This totally negates what Ryan (et. al) have stated in videos on how to properly wire polarized DC breakers.

So, what gives?

Chris

[Robin]

The 250 amp breaker is not polarized. I do not know why it says line and load, but I have it on good authority that they are not polarized. In an inverter hook up it is not possible to connect them correctly if they were polarized anyway. Inverters draw current to inverter, but send current the other direction to charge. That is the same as in a combiner. You can only get it right on one direction. Our MNEPV breakers are indeed polarized. Combiners typically go one direction, but when a PV panel shorts, the current reverses  to blow the breaker in the shorted string. We have tested our combiner breakers with reverse current and they still work fine. CBI is working on non polarized breakers. I have a sample here, but as of yet, no date assigned. They are the same size as our MNEPV breakers except 300V instead of 150.
I saw the MNTBB red on the bench. That is what was intended to bus the controllers together.

[Resthome]

yeah - like dgd says - I don't get why you don't bring battery positive to bottom of big 250 amp  breaker and then the inverter cable goes to top post of that 250 amp breaker.  That is how Midnite  schematic shows to do it  too.


Larry

I attached a picture of what doesn't make sense concerning LINE/LOAD side of polarized DC breakers. Additionally, (following DC breaker LINE/LOAD wiring), the PV + Disconnect is shown backwards too (assuming LINE is on top and LOAD is on the bottom of the breaker). Now (look at second picture), if ALL breakers had their LINE/LOAD labeled the same way then the schematic would be more correct. However, they are not. On the second picture, the ++ on this breaker is the LINE side (per what Ryan said on the video...that goes to the side with the greatest potential...ie, the PV array or battery). And, NO, my breakers are NOT mounted upside down.

Here is a link to Ryan's video explaining DC breakers (start watching at 4:40)
https://www.youtube.com/watch?v=Mtq3cs9Gucc

Okay  Chris - I have a couple breakers here and I see what you mean with the line and load labels. On the smaller DIN rail mounts they have the + on the bottom which would be coming from the source voltage. But as you say the other panel type breaker with studs  is labeled Line on the top and Load on bottom .Guess I never paid attention to those.

I just looked this up and found discussion about this  in the past.
The small Din Rail mount breakers that have the + at the bottom need to be connected to with + to higher voltage source.
The other panel type breakers with studs are not polarity sensitive and you can wire them either way .
Discussion was here
http://midniteftp.com/forum/index.php?topic=3538.msg34227#msg34227

And this is good since I wired my system with panel stud breakers with source voltage at the bottom !  Plus that is the way Midnite shows them wired in photo's of their wiring too.

Larry

Thanks. Two questions:
1) If the C-series (studded) DC breakers are "not polarity sensitive" as you say, WHY are they labeled with LINE and LOAD?
2) Concerning the large 250a breaker...mine is labeled "LINE and LOAD". Is it polarized? If so, LOAD is on the bottom and should go to the inverter...not to the batteries (the Midnite Solar wiring diagram/pictures show THAT is where you put the battery cable on). This totally negates what Ryan (et. al) have stated in videos on how to properly wire polarized DC breakers.

So, what gives?

Chris

Chris,

If you notice in Ryan's video when he talks about Midnite panel mount breakers there is a white text overlay that pops up which states these are not polarity sensitive.  When he talks about Midnite din rail breakers this is where he talks about polarity and current available Midnite din rail breakers need to be wired correctly. This has been mentioned in the forums before.  It could have been made clearer by stating this verbally. For that reason the only place I have Midnite Din rail breakers are in the Combiner box. I use Midnite panel mount breakers for every thing else.

[Jacotenente]

Cool...thanks. I saw/seen that in the video...still doesn't explain why they are labeled LINE/LOAD. Are the new ones Midnite testing labeled that way? Why use DIN-rail DC polarized breakers at all? Pretty sure the Aussie's don't allow them either. Also, just want to say "thanks" to Midnite for all their help/advice with this rebuild and MNDC box. Projecting my system will be back up before Easter Sunday...sucks buying power.

Chris

[Vic]

It has been stated somewhere,   perhaps on this Forum,   that the non-polarized panel-mount breakers have Line and Load markings,   because SO many electricians are accustomed to looking for such markings,   and would question which terminals were line,   and load,  if they were not marked,   so   this was a stated reason.

Also,   it is not clear to me,   that ALL panel-mount breakers are non-polarized.   Wonder about the older Airpax breakers from several decades ago (as were used in the Trace and Xantrex systems)  --  are these panel mount breakers polarity-sensitive?

FWIW,     Vic