Please recommend suitable input/output fusing for Classic controller

SusidoSusido Posts: 32Registered Users ✭✭
Just received a Midnite Solar Classic 150 controller and now realize I am horribly confused as to what I should be using for the solar input and battery output fuses/breakers.

Currently I have only 2 strings of solar panels each consisting of 3 130 watt 12v panels. Panels are 17.6 Pmax (open circuit 21.6V), Imp 7.3A so the 3 in series will produce 52.8V @ 7.3A. So 14.6A after the 2 strings are combined. Battery bank is 24V. Cable size will be 10AWG to the combiner, 6AWG from the combiner to the charge controller and 6AWG from the CC to the battery bank.

I understand I do not need fuse protection with just the 2 strings but will need a fuse/breaker on each string when I do a planned expansion to 3 strings later this year. When that happens I plan on getting a simple Midnite Solar Baby Box (http://www.solar-electric.com/baby-box.html) and use 3 MNEPV 150VDC breakers but I am unsure as to what these breakers should be rated at for my array. I’m guessing 15A.

For now I can just connect the 2 strings in parallel through a plastic combiner box with a couple of buss bars and then on to the charge controller. But don’t I also need a PV disconnect before the charge controller? And this PV disconnect should be what exactly? The Classic owner’s manual on page 76 provides what for me is a real confusing breaker sizing chart but it appears this thing might be what they call the Input Breaker and it might need to be approximately 63A. What would be recommended to perform this function? I thinking another MNEPV 150VDC breaker but this one much larger than the other 3 breakers but mounted in the same Baby Box (assuming a future 3rd string). Or would something like this breaker http://www.solar-electric.com/pamodccibr.html be better - it’s described as panel mount but could this kind of breaker be mounted separately outside the box? Told you I was confused.

As for the Output Breaker (from CC to battery bank): I currently have lying around one of these Bussman circuit breakers with switch (http://www.solar-electric.com/mr60ampdccib.html). But it’s rated at 150A and 48VDC so I guess that is too large a breaker and too small a DC voltage rating right? Would a Class-T fuse of 110A like this one http://www.solar-electric.com/fb110ampfuwi.html be appropriate here? The Classic Breaker sizing chart seem to indicate something between 90-100A be used here but 110A is the smallest Class-T sold at NAW&S.

Anyway I may be seriously off with my assumptions as to what is needed here for fusing/breakers so I really appreciate your advice.
Seasonally off-grid ... 468 Ahrs @ 48V (8 Rolls S-605 6v FLA batteries),  24 x 130watt panels, 6 x 260watt panels, 2 x Midnite Classic 150, Whizbang Jr., Magnum MS4448PAE inverter/charger, 2 x Honda eu2000i generators paralleled.


Comments

  • ChrisOlsonChrisOlson Posts: 1,807Banned ✭✭
    Re: Please recommend suitable input/output fusing for Classic controller

    I guess I would recommend that when you install the classic to use #4 wire and a 100 amp breaker between the Classic and the battery. You can use smaller wire and breaker too, but if you eventually increase the size of your solar you will have to redo it. So may as well put the size in that the Classic needs for it's output rating.

    I would not use a fuse - use a breaker. You need to be able to easily turn it off and on when doing firmware updates in the controller.

    Your solar should have a disconnect near the Classic someplace with a breaker that protects the wire run from the controller to the array combiner. That breaker should be sized appropriately for the size of the wire in the run. Again use a breaker instead of a fuse - it also needs to be turned off when doing a firmware update.
    --
    Chris
  • SusidoSusido Posts: 32Registered Users ✭✭
    Re: Please recommend suitable input/output fusing for Classic controller

    Thanks Chris, 4AWG and a 100A breaker for the charge controller output it is. As far as the input is concerned, that will be a short run of 6AWG from the solar combiner box (eventually to be equipped with 3 12A breakers for each of 3 strings) to the controller. So I'm guessing a 60A 150VDC breaker here might be appropriate. I am planning to install that breaker on the same DIN rail in the combiner box as the other 3 smaller breakers. Hopefully that will be OK.
    Seasonally off-grid ... 468 Ahrs @ 48V (8 Rolls S-605 6v FLA batteries),  24 x 130watt panels, 6 x 260watt panels, 2 x Midnite Classic 150, Whizbang Jr., Magnum MS4448PAE inverter/charger, 2 x Honda eu2000i generators paralleled.


  • VicVic Posts: 2,908Solar Expert ✭✭✭✭
    Re: Please recommend suitable input/output fusing for Classic controller

    Hi Susido,

    As Chris noted, Breakers are the best thing to use for CC in and out Disconnect/protection.

    The Panel Mount breaker you linked in the first post is NOTa DIN-Rail breaker, and will not work well in the Baby Box. PM Breakers mount with screws from the front of the breaker. These PM breakers are very good, and are very rigid due to the screw mounting.

    You could use the MidNite Quad Box for the CC in and CC out breakers. That box:

    http://www.solar-electric.com/mnedc-quad.html

    And choose appropriate PM breakers. Believe that there is now a 100 A PM breaker. These PM and the Din rail breakers need to be mounted vertically, so these boxes are handy. Also, there are limits on the Max wire size for some of these smaller boxes. It is possible that #4 AWG wire is not exactly permitted in the Baby Box ... Forget. But, believe that the Quad box allows #4.

    Believe that everything at Wind-Sun is 10% off on Earth Day, 4/22/13, FWIW.

    Have Fun, Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • SusidoSusido Posts: 32Registered Users ✭✭
    Re: Please recommend suitable input/output fusing for Classic controller

    Thanks for that info Vic, forgot about Earth Day! I'm technically dealing with 5 breakers - three small 12A 150VDC breakers (DIN rail) for solar panel strings, one 150VDC perhaps 60A DIN rail breaker (yes, I had originally proposed a non-DIN rail panel mount breaker for that job) to act as a solar disconnect and provide protection for the wire run from the controller to the array combiner and one 100A breaker for the controller to battery run. That last breaker doesn't need to be particularly high voltage for a 24V battery bank so I am planning on using one of these 48VDC flush mount breakers: http://www.solar-electric.com/mr60ampdccib.html. Besides the first 4 proposed DIN rail breakers would already fill up all the available spaces.

    Good point about the limited space in some of these enclosures. The Big Baby Box sounds more appropriate. And with the 100A breaker on a separate run, there wouldn't be any 4AWG cables in there.
    Seasonally off-grid ... 468 Ahrs @ 48V (8 Rolls S-605 6v FLA batteries),  24 x 130watt panels, 6 x 260watt panels, 2 x Midnite Classic 150, Whizbang Jr., Magnum MS4448PAE inverter/charger, 2 x Honda eu2000i generators paralleled.


  • VicVic Posts: 2,908Solar Expert ✭✭✭✭
    Re: Please recommend suitable input/output fusing for Classic controller

    OK Susido,

    Was uncertain weather the Baby Box combiner would be elsewhere (nearer the PVs) or all together.

    I do have one of those Bussman breakers that you linked, but am personally unimpressed with them, and doubt that they are switch-rated, and may be a Thermal breaker ...

    Just my opinion that the MN Panel Mounts are far superior to the Bussman and even the MN DIN-Rail breakers. To each their own.

    And regarding this sentence in your post,
    "Besides the first 4 proposed DIN rail breakers would already fill up all the available spaces", The Panel-Mount breakers would NOT work in the Baby Box, or any other DIN-Rail only box, as the PMs mount from the front and have different size cutout, anyway. So this would have meant a MN Quad Box, which could accommodate both of the breakers for the CC. And as Chris also mentioned, it is a very good idea to have both of the breakers for the CC mounted (together IMHO) near the CC for convenience and in case of emergency.

    Just my opinions. Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • SusidoSusido Posts: 32Registered Users ✭✭
    Re: Please recommend suitable input/output fusing for Classic controller

    Sorry, I should have mentioned that the combiner box would be near the controller. I see what you mean about having the convenience and reliability of the two Panel-mount breakers in the same box. Do a 100A for output and a 60A for input sound about right to you?

    The only bad thing is that I'll need two enclosures, one DIN rail and one Quad box. Or are there smaller combination boxes with both?
    Seasonally off-grid ... 468 Ahrs @ 48V (8 Rolls S-605 6v FLA batteries),  24 x 130watt panels, 6 x 260watt panels, 2 x Midnite Classic 150, Whizbang Jr., Magnum MS4448PAE inverter/charger, 2 x Honda eu2000i generators paralleled.


  • ChrisOlsonChrisOlson Posts: 1,807Banned ✭✭
    Re: Please recommend suitable input/output fusing for Classic controller
    Susido wrote: »
    Do a 100A for output and a 60A for input sound about right to you?

    That's what I have on all my Classics - #6 in with a 60A breaker and #4 out with a 100A. However, my combiners are out by the solar arrays so I didn't have to run all those little 10 gauge wires into the utility room. And I have a 60 amp disconnect in the utility room for each array. I don't use anywhere close to the 60 amps capacity - the 3.75 kW array runs at usually 40 amps or so and the other one at about 25 amps. But I put the full 60 amp service in from the array combiners in the event of future expansion. Nothing worse than deciding to put in more solar panels and having to pull out wiring and re-do it because the wiring is too small.

    --
    Chris
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