Best way to mount DC breakers?

[WorldwideDave]

Hi friends. I have 4 ground mount arrays. They are 4 parallel strings, about 150VDC each. Each parallel string has its own inline 30A fuse. I plug each string with its fuse into it's own DC breaker box on the input/bottom side. On the output side of each of the DC breaker boxes, I then run the 4 parallel wires into a 4 in 1 MC4 combiner wire (sometimes called a parallel connector or a 4-in-1 dongle or a branch connector). From that 4-in-1 adapter I then run a 100' cable to the side of my house, and plug it into the input side of a PV disconnect box.

I have the four separate plastic DC breaker boxes. Immediately next to the ground arrays I have a cement wall. I need to mount those 4 separate DC breaker boxes. I don't want to buy a combiner box. I have cement wall.

My question is this: Should I :

Option 1.) first attach a piece of wood, paint it to match the wall, then attach the 4 plastic boxes to the wood, OR
Option 2.) attach something else like wonderboard/hardibacker to the wall, then paint it, then mount the 4 plastic boxes to that
Option 3.) bolt the 4 DC breaker boxes directly to the cinder block wall
Option 4.) ??? Input option here

Please let me know in the comments. Thanks for reading, and your replies!

 

[740GLE]

Option 5

Buy a combiner box, seems to be the easiest thing, this is the prime example of why they exist.

 

[WorldwideDave]

Option 5

Buy a combiner box, seems to be the easiest thing, this is the prime example of why they exist.

See above where I say verbatim "I don't want to buy a combiner box".
Cashflow issue.
And *if* I was to buy a combiner box, the exact same problem would exist - how do I mount the box to the cinder block wall. See prior post.

Thanks for reading and responding.

If you feel like you want to ship me a combiner box with 4 DC breakers, my zip code is 90266 for calculating shipping from new Hampshire. /s

 

[42OhmsPA]

I'd use tapcons to mount a combiner box to the wall.
I'd ditch the inline fuses.
I'd ditch the 4 to 1 cable, sounds like to much current is running through it.
You don't need to buy a prebuilt combiner box, you can make your own easy; I'd use Dihool breakers.

Posting photos of what you're working with would probably help a lot, the 4 existing boxes have me confused.

 

[WorldwideDave]

Posting photos of what you're working with would probably help a lot, the 4 existing boxes have me confused.

Sure. Here you go. 8AWG runs to the PV disconnect. They are sitting on a pool heater that is disconnected. Using as a bench for now.

 

[WorldwideDave]

Should note I’ve had zero issues with this configuration. 250V 70A Victron smart MPPT. Small used 200w panels. Never more than about 1010 W can be generated total from all 4 strings on 12V system. All good.

Also I have dc inline fuses so why not use them.

 

[Rocketman]

Most 4-in-1 MC4 combiners have a 30a max rating, is your 4p array, getting close or exceeded the rating on the combiner? Which means the Isc amps on the panel is below 7.5amps.

My plan is to make my own combiner box with Dinkle terminal blocks, these will mount on the rail. I am getting a Vevor outdoor box to mount them in.

My system will be 4S4P.

Each hot wire will go to a fuse, then go to a red terminal block - the four terminal blocks will be connected together with jumpers, then a #8 wire goes to the mppt.

The black wires will go to a black terminal block - connected with jumpers then #8 to the mppt.



For those that don’t know about terminal blocks - here is a photo. Yes I could go with a breaker, but I already have the 12a & 15a fuses.

As long as you don’t need a combiner box, I would drill the cement wall and put a plastic plug in it, then screw the current boxes you have into the plug (sorry I forgot the name of that type of concrete fastener- but all good hardware stores have them).

Good Luck!

 

[WorldwideDave]

Most 4-in-1 MC4 combiners have a 30a max rating, is your 4p array, getting close or exceeded the rating on the combiner? Which means the Isc amps on the panel is below 7.5amps.

My plan is to make my own combiner box with Dinkle terminal blocks, these will mount on the rail. I am getting a Vevor outdoor box to mount them in.

My system will be 4S4P.

Each hot wire will go to a fuse, then go to a red terminal block - the four terminal blocks will be connected together with jumpers, then a #8 wire goes to the mppt.

The black wires will go to a black terminal block - connected with jumpers then #8 to the mppt.

View attachment 312434

For those that don’t know about terminal blocks - here is a photo. Yes I could go with a breaker, but I already have the 12a & 15a fuses.

As long as you don’t need a combiner box, I would drill the cement wall and put a plastic plug in it, then screw the current boxes you have into the plug (sorry I forgot the name of that type of concrete fastener- but all good hardware stores have them).

Good Luck!

Each panel is 7.1 max amps I believe. 4s4p for me. So I think each parallel string is max of 7.1 but call it 7.5 just in case. 4 strings is 30A exactly.

Not sure on the 4 in one rating.

Any other suggestions?

 

[glandpuck]

What you need to do is simple. Create a combiner box using a standard DIN rail for the mounts. Get a UL listed NEMA 3R enclosure. Install the DIN rail. Mount DIN rail solar fuse holders and UL solar fuses of the correct amperage for your string and fuse the PV+ and PV-. Then add a DIN mount double pole DC breaker of the correct amperage and voltage. Midnite Solar is an excellent source for this. Again the PV+ and PV- pass through the breaker. Then the fused and breakered PV+ and PV- pass through a real DC disconnect of the proper amperage to prevent arcing. From the disconnect switch to the MPPT input of the inverter. the panel and array ground to your common ground point near the inverter.

 

[740GLE]

Each panel is 7.1 max amps I believe. 4s4p for me. So I think each parallel string is max of 7.1 but call it 7.5 just in case. 4 strings is 30A exactly.

Not sure on the 4 in one rating.

Any other suggestions?

With a 250v SCC can you maybe do 5s or 6s?

Or is there partial shading/ arrays pointing different directions?

 

[42OhmsPA]

Sure. Here you go. 8AWG runs to the PV disconnect. They are sitting on a pool heater that is disconnected. Using as a bench for now.

Yea, I know it's not what you want to hear but I would clean all that up and go the route @glandpuck suggested, that's the same route I went with mine.
Each string into the combiner to parallel, out to a main disconnect and out to the SCC.
They make boxes like the one I attached in multiple sizes, some even have the bus bars to combine strings included.

 

[TM48]

4 parallel wires into a 4 in 1 MC4 combiner wire

How much current are you feeding though that MC4 quad combiner? Most are only rated for 30 amps and many are sketchy at that. As far as the four boxes I would just tapcon them directly to the cement wall. Simpler, nothing to paint or rot and will look better.

 

[chrisski]

I attached my one box direct to the cinder wall

 

[K&M]

I wouldn’t use wood behind the breaker boxes. It’s only gonna last so long.

I would either

A. Use Tapcons to attach the breaker boxes directly to the cinder blocks.

B. Use something that will never rot such as pvc trim boards. https://www.lowes.com/pd/Metrie-PVC-Trim-Board-3-4-In-x-5-1-2-In-x-8-Ft/5013353105

 

[SplitUniverse]

Most 4-in-1 MC4 combiners have a 30a max rating, is your 4p array, getting close or exceeded the rating on the combiner? Which means the Isc amps on the panel is below 7.5amps.

My plan is to make my own combiner box with Dinkle terminal blocks, these will mount on the rail. I am getting a Vevor outdoor box to mount them in.

My system will be 4S4P.

Each hot wire will go to a fuse, then go to a red terminal block - the four terminal blocks will be connected together with jumpers, then a #8 wire goes to the mppt.

The black wires will go to a black terminal block - connected with jumpers then #8 to the mppt.

View attachment 312434

For those that don’t know about terminal blocks - here is a photo. Yes I could go with a breaker, but I already have the 12a & 15a fuses.

As long as you don’t need a combiner box, I would drill the cement wall and put a plastic plug in it, then screw the current boxes you have into the plug (sorry I forgot the name of that type of concrete fastener- but all good hardware stores have them).

Good Luck!

If that picture is representative of your "fuses"you plan to use I would think twice. At 4P you are around 200V and those fuses look like they are just small enough to maintain an arc at that voltage; once started a 200V arc can easily span 1/2in in air. It would really suck to make such a nice contraption just to wake up with it melted into a blob the first time your fuse blows.

 

[Brucey]

Hi friends. I have 4 ground mount arrays. They are 4 parallel strings, about 150VDC each. Each parallel string has its own inline 30A fuse. I plug each string with its fuse into it's own DC breaker box on the input/bottom side. On the output side of each of the DC breaker boxes, I then run the 4 parallel wires into a 4 in 1 MC4 combiner wire (sometimes called a parallel connector or a 4-in-1 dongle or a branch connector). From that 4-in-1 adapter I then run a 100' cable to the side of my house, and plug it into the input side of a PV disconnect box.

The 4 into 1 "branch connector" should be set aside. Fire risk.

Ideally you'd have an mnpv6 combiner enclosure like this.

MidNite Solar MNPV3 / MNPV6 / MNPV12 Combiner Breaker Box

Midnite Solar's MNPV series of combiner boxes facilitate the flexibility and safety that solar arrays require. Whether you have a small array with just a couple strings, or a large array of up to 12 strings, the MNPV series provides solutions to problems often overlooked. Common Applications...

www.currentconnected.com

But its expensive. So you can just get the breakers and the busbar that will connect to the top of the breakers.

Get four of these:

MidNite Solar MNEPV10-150-1PNP Circuit Breaker 10A 150VDC

Shop now for MidNite Solar MNEPV10-150-1PNP Circuit Breaker 10A 150VDC 1P.

www.stellavolta.com

And one of these:

MidNite Solar MNPV6-BREAKER-BB Copper Busbar 120A

Shop now for MidNite Solar MNPV6-BREAKER-BB Copper Busbar 120A.

www.stellavolta.com

Note these breakers are 10A, based on your 7A string currents. Your 30A dc breakers will never fulfill any ocp functionality.

Attach the breakers to a din rail from a vendor of your choice. Run your home run from the bus bar back to the scc. Could use something like this for the negatives:

MidNite Solar MNSBB-B Short Busbar

Shop now for MidNite Solar Short Busbar MNSBB-B in Black. For PV+ input on the narrow OB E-Panel and for a separate PV bus bar for charge controllers.

www.stellavolta.com

You have per string disconnect and ocp with these breakers. Note they have 1PNP at the end of their model name which designates non polarized.

May want to consider adding an spd300 when funds permit for surge protection.

This is assuming your string voltage is below 150V if not you'll need different breakers.

 

[Crowz]

The 4 into 1 "branch connector" should be set aside. Fire risk.

Ideally you'd have an mnpv6 combiner enclosure like this.

MidNite Solar MNPV3 / MNPV6 / MNPV12 Combiner Breaker Box

Midnite Solar's MNPV series of combiner boxes facilitate the flexibility and safety that solar arrays require. Whether you have a small array with just a couple strings, or a large array of up to 12 strings, the MNPV series provides solutions to problems often overlooked. Common Applications...

www.currentconnected.com

View attachment 312500

But its expensive. So you can just get the breakers and the busbar that will connect to the top of the breakers.

Get four of these:

MidNite Solar MNEPV10-150-1PNP Circuit Breaker 10A 150VDC

Shop now for MidNite Solar MNEPV10-150-1PNP Circuit Breaker 10A 150VDC 1P.

www.stellavolta.com

And one of these:

MidNite Solar MNPV6-BREAKER-BB Copper Busbar 120A

Shop now for MidNite Solar MNPV6-BREAKER-BB Copper Busbar 120A.

www.stellavolta.com

Note these breakers are 10A, based on your 7A string currents. Your 30A dc breakers will never fulfill any ocp functionality.

Attach the breakers to a din rail from a vendor of your choice. Run your home run from the bus bar back to the scc. Could use something like this for the negatives:

MidNite Solar MNSBB-B Short Busbar

Shop now for MidNite Solar Short Busbar MNSBB-B in Black. For PV+ input on the narrow OB E-Panel and for a separate PV bus bar for charge controllers.

www.stellavolta.com

You have per string disconnect and ocp with these breakers. Note they have 1PNP at the end of their model name which designates non polarized.

May want to consider adding an spd300 when funds permit for surge protection.

I need to go retrieve one of those combiner boxes at the old house. I just remembered I had put one on the side of the house there years ago that isn't being used now

 

[WorldwideDave]

With a 250v SCC can you maybe do 5s or 6s?

Or is there partial shading/ arrays pointing different directions?

Two of the point One Direction two of them point another.

 

[WorldwideDave]

Yea, I know it's not what you want to hear but I would clean all that up and go the route @glandpuck suggested, that's the same route I went with mine.
Each string into the combiner to parallel, out to a main disconnect and out to the SCC.
They make boxes like the one I attached in multiple sizes, some even have the bus bars to combine strings included.
View attachment 312486

It is messing because I’m waiting for a mounting solution. Tidy and buying more stuff doesn’t solve mounting problems but it sure looks cool.

 

[WorldwideDave]

I attached my one box direct to the cinder wallView attachment 312491

You made my day thanks. Like the brown wall.

 

[WorldwideDave]

I wouldn’t use wood behind the breaker boxes. It’s only gonna last so long.

I would either

A. Use Tapcons to attach the breaker boxes directly to the cinder blocks.

B. Use something that will never rot such as pvc trim boards. https://www.lowes.com/pd/Metrie-PVC-Trim-Board-3-4-In-x-5-1-2-In-x-8-Ft/5013353105

Tapcons for the win.
PVC trim board unique approach.

 

[WorldwideDave]

The 4 into 1 "branch connector" should be set aside. Fire risk.

Ideally you'd have an mnpv6 combiner enclosure like this.

MidNite Solar MNPV3 / MNPV6 / MNPV12 Combiner Breaker Box

Midnite Solar's MNPV series of combiner boxes facilitate the flexibility and safety that solar arrays require. Whether you have a small array with just a couple strings, or a large array of up to 12 strings, the MNPV series provides solutions to problems often overlooked. Common Applications...

www.currentconnected.com

View attachment 312500

But its expensive. So you can just get the breakers and the busbar that will connect to the top of the breakers.

Get four of these:

MidNite Solar MNEPV10-150-1PNP Circuit Breaker 10A 150VDC

Shop now for MidNite Solar MNEPV10-150-1PNP Circuit Breaker 10A 150VDC 1P.

www.stellavolta.com

And one of these:

MidNite Solar MNPV6-BREAKER-BB Copper Busbar 120A

Shop now for MidNite Solar MNPV6-BREAKER-BB Copper Busbar 120A.

www.stellavolta.com

Note these breakers are 10A, based on your 7A string currents. Your 30A dc breakers will never fulfill any ocp functionality.

Attach the breakers to a din rail from a vendor of your choice. Run your home run from the bus bar back to the scc. Could use something like this for the negatives:

MidNite Solar MNSBB-B Short Busbar

Shop now for MidNite Solar Short Busbar MNSBB-B in Black. For PV+ input on the narrow OB E-Panel and for a separate PV bus bar for charge controllers.

www.stellavolta.com

You have per string disconnect and ocp with these breakers. Note they have 1PNP at the end of their model name which designates non polarized.

May want to consider adding an spd300 when funds permit for surge protection.

This is assuming your string voltage is below 150V if not you'll need different breakers.

120 bucks plus shipping and a box of my choice. Hmmm. But better than a fire. Total voltage now is at 150 or so. Mppt supports 250. It’s at 12v. Not sure if going to 48v changes the string voltage or not but I don’t think so.

 

[42OhmsPA]

It is messing because I’m waiting for a mounting solution. Tidy and buying more stuff doesn’t solve mounting problems but it sure looks cool.

Tapcons that many have mentioned work great. Do you have a hammer drill and rotary masonary bits?

Edit - wrong bit typed.

 

[glandpuck]

Yea, I know it's not what you want to hear but I would clean all that up and go the route @glandpuck suggested, that's the same route I went with mine.
Each string into the combiner to parallel, out to a main disconnect and out to the SCC.
They make boxes like the one I attached in multiple sizes, some even have the bus bars to combine strings included.
View attachment 312486

HERE IS MY CAUTIONARY TALE: I tried an Amazon Chinese 50 amp bypass breaker and before it was near acceptable limits, it melted and shorted sending 240 volts through my 120 volt lines and blew up multiple surge protectors and transformers in gate openers, swimming pool controller, irrigation controllers, HVAC, etc. Cost me over 1K to replace and repair everything. So I look for the UL rated devices only now.

 

[glandpuck]

Tapcons that many have mentioned work great. Do you have a hammer drill and rotary bits?

Masonry bit. You can also use the masonry bit and hammer drill to then insert the plastic sleeve liner and thread into that. Depends on loads. For big bolts into concrete, then you are talking SDS or SDS Max drill and concrete bits and Simpson concrete bolts.