Which came first, the chicken or the egg? In my case, the charge controller or DC shut off switch

showmeshowme Registered Users Posts: 63 ✭✭
edited May 15 in Solar Beginners Corner #1

ok, so posting in the beginner's forum still doesn't make it easy to ask a question I figure everyone but me already knows, but this is where I've gotten to, and I need a little information on how and why it's suppose to go this way. For some reason, I've assumed the array needed to go through the charge controller before it hits the DC shut off, but I'm seeing now that it's not that way? Could somebody explain to me in layman's language about why, if there are shut off breakers in the combiner box and another breaker for the array at the DC circuit breaker box, it needs to go through another step before the mppt  cc (MS Classic 150)?

To be honest here, I have not re-read the manual, which is for a NOS Trace Xantrex dual SW5548, and the power panel that it will be mounted on. I know, I know. I'd just like to hear it from someone who may have, at one time, been ignorant, too. Thanks, Lee

"Knowing is not enough, we must apply. Willing is not enough, we must do."   Goethe

NOS Trace Xantrex power panel, (3) Trace Xantrex SW5548's (2 NOS in boxes, one used), Xantrex DC/disconnect, AC disconnect/conversion, Xantrex T240 Auto transformer, (3) C40 PWM charge controllers, (2 NOS, one used)  8k LG Neon 320w, (8)Evergreen  Solar 120w (960w)  , Bergey XL.1 1.5k genny, AirX 400 genny, 48v Interstate Workman batts (frozen/toast), (2) MT Solar Top of Pole 12's, (2) Midnite Solar MSPV 4 combiner boxes, (2) Midnite Solar Classic 150's and one nice Ozark hilltop to set them all.


Comments

  • PhotowhitPhotowhit Solar Expert Posts: 5,824 ✭✭✭✭✭
    showme said:
    Could somebody explain to me in layman's language about why, if there are shut off breakers in the combiner box and another breaker for the array at the DC circuit breaker box, it needs to go through another step before the mppt  cc (MS Classic 150)?d on. I know, 
    It's so you can isolate the charge controller.

    So you would have breakers or fuses at the combiner box, which might be 1000's of feet from the power center (where the charge controller, batteries and inverter are). If you have a combiner box in the power center, I'd suggest you don't need another shutoff before the charge controller.  But having one before the charge controller allows you to shut of energy coming from the solar array, having a breaker between the battery and the charge controller allows you to shut off power from the battery.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
  • showmeshowme Registered Users Posts: 63 ✭✭
    edited May 16 #3

    As of right now (until we get the house built and the power center switched over), the arrays will be 15' from the power center, so the combiner box shut off will be close to the DC disconnect box and the two cc's. After that, there will be a 270' run between the arrays/combiner boxes and the power center.

    So, when you speak of having that breaker between the combiner box and the charge controller, the DC disconnect box has two separate breakers/kill switches. There is an array shut off switch, then the DC disconnect breaker. I can see how the array should feed through the array disconnect before running through the cc, but it seems the manual is saying that the array should go through the DC disconnect breaker before the cc. (is that correct, or am I missing something there?) I understand this box also connects to the batteries, but it looks like it's all over the place when it gets into the disconnect box. What exactly is the route from the array to the inverter? Is it Array>array shut off>charge controller>battery>DC disconnect? or Array>array shut off switch>DC disconnect>cc>batteries, or what?

    Oddly enough, I've worked around electricity as a welder and re-habber of old houses for most of my adult life, but now that I'm into solar and wind, I feel like a 1st grader in a physics class. It is really hard for me to wrap my head around. Even after taking classes in DC electrical math. I think I'm missing an important "electrical gene". 

    "Knowing is not enough, we must apply. Willing is not enough, we must do."   Goethe

    NOS Trace Xantrex power panel, (3) Trace Xantrex SW5548's (2 NOS in boxes, one used), Xantrex DC/disconnect, AC disconnect/conversion, Xantrex T240 Auto transformer, (3) C40 PWM charge controllers, (2 NOS, one used)  8k LG Neon 320w, (8)Evergreen  Solar 120w (960w)  , Bergey XL.1 1.5k genny, AirX 400 genny, 48v Interstate Workman batts (frozen/toast), (2) MT Solar Top of Pole 12's, (2) Midnite Solar MSPV 4 combiner boxes, (2) Midnite Solar Classic 150's and one nice Ozark hilltop to set them all.


  • PhotowhitPhotowhit Solar Expert Posts: 5,824 ✭✭✭✭✭
    Basically think of the Array being connected to the battery and the inverter connected to the battery. I don't understand what you are referring to as a "...array shut off switch...".  I will use a breaker as required. I do have a 'switch' on my old inverter, not sure there is a 'switch' on any charge controller I've owned.

    At the risk of confusing things... This is my 'E-Panel' a Midnite product designed to hold breakers for your system. It doesn't have an AC breaker as pictured, but has one now in the open DIN rail. The side by side pictures are marked with the path of the current;


    The Array wiring comes in from the back at the top.

    Then the energy comes from the charge controllers back to through the breaker box/E-Panel to the other breakers at the top left;

    You can consider the Busbars as the battery.

    Here is an overview of the Power center, the battery is to the right, follow the big cables...lol.
    My old inverter is the yellow and grey box to the left. It's still there, but I use a Magnum 4024 mounted above it now.



    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
  • littleharbor2littleharbor2 Solar Expert Posts: 1,698 ✭✭✭✭
    Typically the combiner is with the array and will have PV fuses or DC rated breakers on each individual string. Exiting the combiner would be a pair of  appropriately sized wires. These would come into some sort of enclosure with a higher current rated breaker to accommodate the current of all combined strings. Here's a couple photos of my setup and another box. The array lines enter then exit the box and go to the SCC. The output of the SCC to the battery again enters and exits the breaker box and heads to the buss bars or battery depending on how your set up is arranged. This gives you the ability to shut down the system for maintenance, troubleshooting or whatever you need to do. 
     Note the breaker for the SCC output should be the next size up from the expected output of the SCC. In the event of Cloud Edge Effect insolation you can experience higher than expected current which can pop the breaker and essentially shut down your system. Luckily the two times it happened to me I was standing in front of the controller watching and saw this happen. I could have been back in California for the month and come home to a big mess. If you can see from one of these photos there's an 80 amp breaker in the battery output location. Had a 60 before figuring my array wouldnt ever put out more than 60 amps. Those 80 amp single pole breakers aren't easy to find. 

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

  • PhotowhitPhotowhit Solar Expert Posts: 5,824 ✭✭✭✭✭
    Had a 60 before figuring my array wouldnt ever put out more than 60 amps. Those 80 amp single pole breakers aren't easy to find. 
    I think we have discussed this before...

    The Square D breakers are rated for something like 50 volts DC and with a Midnite 200 charge controller, I would assume a much higher voltage coming in... Indeed a 2100 watt array going through a 15 amp breaker would be something like 100+ volts...

    ...something to ponder.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
  • littleharbor2littleharbor2 Solar Expert Posts: 1,698 ✭✭✭✭
    edited May 16 #7
    Photowhit said:
    Had a 60 before figuring my array wouldnt ever put out more than 60 amps. Those 80 amp single pole breakers aren't easy to find. 
    I think we have discussed this before...

    The Square D breakers are rated for something like 50 volts DC and with a Midnite 200 charge controller, I would assume a much higher voltage coming in... Indeed a 2100 watt array going through a 15 amp breaker would be something like 100+ volts...

    ...something to ponder.
     That's why you see the midnite solar double wide 300 volt  breaker on the incoming line here.

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

  • PhotowhitPhotowhit Solar Expert Posts: 5,824 ✭✭✭✭✭
    Very confused about what is the "array" in the other picture...
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
  • littleharbor2littleharbor2 Solar Expert Posts: 1,698 ✭✭✭✭
    Photowhit said:
    Very confused about what is the "array" in the other picture...
    There isn't an array connected. I just pulled that as another example from my old stuff. That was likely connected to a low voltage array long ago.

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

  • showmeshowme Registered Users Posts: 63 ✭✭
    edited May 18 #10

    Wow. It's going to take a while for me to peruse this information and let it soak in. I know that sounds silly to anyone who is 'in tune' with this information, but my head starts to spin as soon as I try to decipher it. But thank you PW and LH2 for all of this good stuff and the pics, too.

    Per my inability to register electrical theory easily, I often think about another problem I've had before. When I was in my mid 20's back in the early 80's my younger brother and I moved to Texas to find work, since there was nothing in Missouri. We found jobs at Dow Chemical in Freeport, TX at the infamous "Red Planet" in the plant where catalyst pills for Dow's styrene (styrafoam) were produced. It was basically an automated plant that created those pills out of a slurry of iron oxide and a lot of other ingredients, but there was a process of starting up the system's kiln, augers, etc. which was done on a huge board with more lights and switches than I could count. It was a simple (to everyone else, including my brother) start up system that had to be done exactly right, or it would shut everything down. I was just flabbergasted by how I could not get it right, no matter what I did. And I consider myself an intelligent person! But that "simple" process haunted me the whole time I worked at that nasty place. I would literally sweat red for days at Surfside Beach or the pool when I was off. Anyway, that's about when I realized that I am not wired for some things. Once I get something down, I'm fine. But it's just the idea that I can't grasp a thing when it's right in front of me sometimes. Like riding a bike, once your over the hump you wonder what kept you from 'getting it' before.

    Mike, you've helped me before and you are correct, we've discussed the importance of over powering breakers and the problems with going over the limits by different effects (cold, brightness, etc.), and the damage it can do on undersized equipment. That I can understand. I'm just trying to figure out the elements of the flow path and how it is affected by everything else in the system, along with my (still) difficulty in completely understanding electrical math.

    I know this may not help, but for the sake of clarity of what I'm working with, I'm putting a couple of pics of what I have and what I intend to end up with on the wall. The first pic is the ad for what I bought years back in anticipation of going off grid, and a second pic of what mine will end up being, which Robin Gudgel use to own.. Oddly enough, even though it may be considered "antiquated" to some, it was a system that he (Robin) had in his early days. Unfortunately, in order to store it I had to dismantle the systems parts, so I can't give you any good pics (until I dig them out of a box I've stored somewhere) of the original power board wiring. Right now all the equipment is layed out on a big table. But I will get back here as soon as I've studied your replies. Sometimes I have to laugh at myself. I can get out a blueprint of a power house, a car plant, a brewery, a bridge- and know exactly what needs done from A-Z, but when I do the same with this system, it's like I've never seen a wire before. But that's what I'm on this forum for. A way out of my fog.

      


    "Knowing is not enough, we must apply. Willing is not enough, we must do."   Goethe

    NOS Trace Xantrex power panel, (3) Trace Xantrex SW5548's (2 NOS in boxes, one used), Xantrex DC/disconnect, AC disconnect/conversion, Xantrex T240 Auto transformer, (3) C40 PWM charge controllers, (2 NOS, one used)  8k LG Neon 320w, (8)Evergreen  Solar 120w (960w)  , Bergey XL.1 1.5k genny, AirX 400 genny, 48v Interstate Workman batts (frozen/toast), (2) MT Solar Top of Pole 12's, (2) Midnite Solar MSPV 4 combiner boxes, (2) Midnite Solar Classic 150's and one nice Ozark hilltop to set them all.


  • showmeshowme Registered Users Posts: 63 ✭✭

    Sitting here studying the replies, and thought I'd post a pic of the breaker in question. I didn't mention that I'd already bought two new MNEDC60 breakers, which I now won't use. After ordering them, they were the wrong size (dimensions) anyway. The intent is to have 2 new of everything and keep the old single originals for back up. Here's the original array breaker


    Sorry about the gigantic pics. I even downsized them. At least they're readable.

    "Knowing is not enough, we must apply. Willing is not enough, we must do."   Goethe

    NOS Trace Xantrex power panel, (3) Trace Xantrex SW5548's (2 NOS in boxes, one used), Xantrex DC/disconnect, AC disconnect/conversion, Xantrex T240 Auto transformer, (3) C40 PWM charge controllers, (2 NOS, one used)  8k LG Neon 320w, (8)Evergreen  Solar 120w (960w)  , Bergey XL.1 1.5k genny, AirX 400 genny, 48v Interstate Workman batts (frozen/toast), (2) MT Solar Top of Pole 12's, (2) Midnite Solar MSPV 4 combiner boxes, (2) Midnite Solar Classic 150's and one nice Ozark hilltop to set them all.


Sign In or Register to comment.