Help with building a dc breaker box

[outlaw525s1991]

I have 6 100w 12v mighty max polycrystalline solar panels connected through a 6 string combiner box(1 panel connected to each string, I did this so they were fused). I want a db ‘load center’ inside my cabin. I would like a breaker that the incoming power from the combiner box runs into first not only acting as a breaker but also as a disconnect; I want it this way so I can disconnect the incoming power from inside incase I ever needed to, instead of having to run outside quick, say incase of a emergency. I have a 50amp pwm controller, which honestly is probably at its max if I where to get 100% perfect performance, which to date has not happened. My battery bank is undersized right now due to the system obviously not being complete. I have 2x100ah deep cycle lead acid batteries connected in parallel, giving me a 12v 200ah bank. My inverter is a 2000w pure sine wave Jupiter inverter from harbor freight. I’d like everything that needs a fuse and or breaker to have one. I’d rather have a breaker box just for the looks but if fuses are better I honestly don’t care as long as it’s going to be protected(the wires). The system is used lightly mainly to discharge and recharge the batteries so they are not just sitting. I am just about ready to give up on trying to figure out how to do this. Thank you for your help I seriously appreciate it. Have a happy and safe thanksgiving.
Sincerely; allen



Ps: I’ve attached inverter specs and panel specs

 

[littleharbor2]

This is what is commonly used for incoming PV and from SCC to battery.

 

[OzSolar]

I would like a breaker that the incoming power from the combiner box runs into first not only acting as a breaker but also as a disconnect;

If you already have breakers in your combiner box then you could just use a safety switch for the disconnect. Something like the below switch from Siemens should be just right. We often use them for array disconnects as it's rated for DC up to 250v but I have a hunch it could easily deal with much higher voltages.

Siemens General Duty 60 Amp 2-Pole 2-Wire 240-Volt Non-Fusible Outdoor Safety Switch LNF222RA - The Home Depot

General Duty Safety Switches are intended for applications where reliable performance and continuity of service are needed, but where duty requirements are not severe and usual service conditions prevail.

www.homedepot.com

Since you have a 12V system you can use readily available Square D QO breaker box breakers (not Homeline). They are rated for DC use in systems up to 36volts. I've built a lot of power centers for 12 and 24v cabins with them.

This is what is commonly used for incoming PV and from SCC to battery.

**for applications under 48V. I'll mention (again) that it's not for systems over 36v unless you are switching both neg and pos and 70 amps or under. I'd be curious how others interpret this tech note from Schneider regarding up 125vDC applications.

Nice work getting that DIN rail breaker in that box.

edit: to fix broken link

 

[littleharbor2]

If you already have breakers in your combiner box then you could just use a safety switch for the disconnect. Something like the below switch from Siemens should be just right. We often use them for array disconnects as it's rated for DC up to 250v but I have a hunch it could easily deal with much higher voltages.

https://www.homedepot.com/p/Siemens-General-Duty-60-Amp-2-Pole-2-Wire-240-Volt-Non-Fusible-Outdoor-Safety-Switch-RBPU-LNF222RAU/309777796/

Since you have a 12V system you can use readily available Square D QO breaker box breakers (not Homeline). They are rated for DC use in systems up to 36volts. I've built a lot of power centers for 12 and 24v cabins with them.


**for applications under 48V. I'll mention (again) that it's not for systems over 36v unless you are switching both neg and pos and 70 amps or under. I'd be curious how others interpret this tech note from Schneider regarding up 125vDC applications.

Nice work getting that DIN rail breaker in that box.

Most systems these days have high voltage MPPT inputs. Of you look at the breaker on the right side of the first photo, it is rated for 300 Vdc. The breaker on the left is a Square D QOU breaker which are fine for 48 Vdc. systems.

Just a matter of mounting the din rail out far enough off the back of the box to hold the breakers where they need to be.

 

[chrisski]

I have 2x100ah deep cycle lead acid batteries connected in parallel, giving me a 12v 200ah bank.

Is the PWM pusing too much power for the batteries?

The lead acid banks I used had a 10% - 30% OC the C20 charge rate. So with the SCC capable of pushing 50 amps, the battery itself probably takes between max of 20 amps to 60 amps because of the max charging rate.

 

[timselectric]

I'd be curious how others interpret this tech note from Schneider regarding up 125vDC applications.

Yes, two pole required.

 

[OzSolar]

Of you look at the breaker on the right side of the first photo, it is rated for 300 Vdc.

I've installed hundreds of them but what what you've done is complete hack and should not be shown as an example.

The breaker on the left is a Square D QOU breaker which are fine for 48 Vdc. systems.

No it's not.

 

[littleharbor2]

I've installed hundreds of them but what what you've done is complete hack and should not be shown as an example.


No it's not.

Gee thanks. This is a DIY forum and this example is something I built about 12 years ago and it has been working fine for me.

 

[timselectric]

No it's not.

That one (80a) is rated for 60vdc.

 

[ghostwriter66]

https://www.homedepot.com/p/Siemens-General-Duty-60-Amp-2-Pole-2-Wire-240-Volt-Non-Fusible-Outdoor-Safety-Switch-RBPU-LNF222RAU/309777796/

Hmm...looks like the product you're searching for is not available.

 

[ghostwriter66]

Gee thanks. This is a DIY forum and this example is something I built about 12 years ago and it has been working fine for me.

file:///C:/Users/Littleharbor2/Downloads/QOU%20Unit%20Mount%20Circuit%20Breakers_QOU115.pdf

the file is on YOUR hard drive -- we do not have access .....

 

[littleharbor2]

the file is on YOUR hard drive -- we do not have access .....

Thanks

 

[OzSolar]

That one (80a) is rated for 60vdc.

The way I read it the 80a has no DC rating from Square D, not even 48v. Do you have something from Schneider that says differently than below?

https://iportal2.schneider-electric.com/Contents/docs/0100CT1501_SEC-07.PDF

What manufacturer reps have shared at professional development workshops that I've attended is that when solar folks talk about 48v they are generally referring to 48v nominal but when Square D talks about it they mean up to 48v. It has confused many people, including me.

Similar to BlueSeas until recently having a very hard 48V limit on thier 48V product. I called thier tech support about if their 48V products could be used in 48v nominal systems and NO was the answer. Now I see they have a 58v rating.

Here's an informative post from someone else that has also done thier research on this. They even go as far as saying 32v is the hard limit for Square D QO.

Hmm...looks like the product you're searching for is not available.

Hmnn... let's try it again. Thanks for pointing that out. Fixed in my prior post as well.

Siemens General Duty 60 Amp 2-Pole 2-Wire 240-Volt Non-Fusible Outdoor Safety Switch LNF222RA - The Home Depot

General Duty Safety Switches are intended for applications where reliable performance and continuity of service are needed, but where duty requirements are not severe and usual service conditions prevail.

www.homedepot.com

 

[timselectric]

The way I read it the 80a has no DC rating from Square D, not even 48v. Do you have something from Schneider that says differently?

From data bulletin 0601DB0401

 

[timselectric]

Just realized that you were looking at QO & QOB.
Instead of QOU breaker.

 

[OzSolar]

Gee thanks. This is a DIY forum and this example is something I built about 12 years ago and it has been working fine for me.

Product data sheet Specifications Mini circuit breaker, QOU, 15A, 1pole, 120/240VAC, 10kAQOU115 lugs, load side[Ue] rated operational voltage 120/240 V AC120 V AC48 V DC Mounting Mode Unit mount AWG gauge AWG 14...AWG 2 aluminium/co

Is that really a QOU in that box? I don't think I've ever seen a QOU in a factory box like that so I just automatically thought it was a QO. The label that I can read in your picture calls those QO boxes. DIY is fine but if you are going to modify a QO breaker box to take QOU's then it would be important to point that out.

Working fine for 12 years is not the same as using equipment that is designed and UL listed for the job. Once you modified that QO box to put QOU's and Midnight breakers in there you made something that is not UL listed for the job. A savvy inspector (if one is required) might catch that and reject it.

Just realized that you were looking at QO & QOB.
Instead of QOU breaker.

Yep, I just caught that as well.

DIY'ers are going to have a (much) harder time finding and using the DIN rail mounted QOU breakers. Not exactly DIY friendly from an installation or price standpoint.

My local supply houses don't stock them last time I needed one I had to order it. If people are aren't careful, as illustrated by what I just did, they could easily assume the QO at their local big store is what's being talking about in this thread.

 

[timselectric]

Yep, I just caught that as well.

DIY'ers are going to have a (much) harder time finding and using the DIN rail mounted QOU breakers. Not exactly DIY friendly from an installation or price standpoint.

My local supply houses don't stock them last time I needed one I had to order it. If people are aren't careful, as illustrated by what I just did, they could easily assume the QO at their local big store is what's being talking about in this thread.

All true.
But diy'ers don't always know what they need. And easily make similar mistakes in many parts of the system.
All that we can do is try to help them find the right products for their needs.
And it's reciprocal. We all gain from this forum.

 

[outlaw525s1991]

If you already have breakers in your combiner box then you could just use a safety switch for the disconnect. Something like the below switch from Siemens should be just right. We often use them for array disconnects as it's rated for DC up to 250v but I have a hunch it could easily deal with much higher voltages.

Siemens General Duty 60 Amp 2-Pole 2-Wire 240-Volt Non-Fusible Outdoor Safety Switch LNF222RA - The Home Depot

General Duty Safety Switches are intended for applications where reliable performance and continuity of service are needed, but where duty requirements are not severe and usual service conditions prevail.

www.homedepot.com

Since you have a 12V system you can use readily available Square D QO breaker box breakers (not Homeline). They are rated for DC use in systems up to 36volts. I've built a lot of power centers for 12 and 24v cabins with them.


**for applications under 48V. I'll mention (again) that it's not for systems over 36v unless you are switching both neg and pos and 70 amps or under. I'd be curious how others interpret this tech note from Schneider regarding up 125vDC applications.

Nice work getting that DIN rail breaker in that box.

edit: to fix broken link

So any of the square D QO breakers and breaker box are dc rated? I read that but wasn’t sure if that was still the case. The article I found was from years ago. I would much rather use a Square d box and brakers due to that being what my main load center is so would look uniform together inside the control room. Thank you

 

[outlaw525s1991]

Is the PWM pusing too much power for the batteries?

The lead acid banks I used had a 10% - 30% OC the C20 charge rate. So with the SCC capable of pushing 50 amps, the battery itself probably takes between max of 20 amps to 60 amps because of the max charging rate.

I’m not sure what you are asking me? My bank is normally fully charged. Although the cheap PWM charge controller I have is garbage and needs to be upgraded as soon as I can. I also need 4 more 100ah batteries to be where my bank should be. I just wanted a “load” center inside my cabin not only yo stop the incoming pv power if needed but also as a way to have my battery bank,charge controller and inverter all under their own breaker just for protection. Maybe I should just use fuses instead? Idk I have been trying to figure out the most cost efficient way and right now nothing on the inside is protected only the panels running through the combiner box. I just don’t like the fact I don’t have any sort of protection and I’m new to all of this and have never really done it so I have been learning as I go. I made this post out of frustration the other night trying to figure out a list of things I need to build the “load” center. Honestly think I’m just going to run some fuses and call it good for now and once I learn more and have more knowledge I’ll build an actual dc breaker box. Right now I just clearly do not have the knowledge to do so.

 

[chrisski]

I’m not sure what you are asking me?

What is the max charge rate of your each of Your batteries? If you exceed that, you could be killing your lead acid battery.

This is from a data sheet for a flooded lead acid battery bank:

Your number, percentage, will be different.

With this battery, it can’t be charged more than 13 amp per 100 ah of capacity. You have 200 ah of battery, and if the spec is the same as above, the max charge rate is 23 amps. With a 50 amp MPPT, you could exceed that 23 amp rate.

With 600 watts of panels you could push 50 amps while charging to the batteries, exceeding the rate.

On a good day, you could realistically see 36 amps from the panels, still exceeding the max rate.