Solar Secrets & Hacks - DIY Solar Combiner Box 

You are welcome. Thanks for watching!

Yes, safety is always first.

You are welcome, Curtis! Thanks for watching.

You are welcome! I appreciate that. Thanks for watching and subscribing!

Haha that makes sense. But there are lots of other great ones that will help you understand some of the stuff we have been emailing back and forth about!

@@LDSreliance cool + thnx :D

You can't go wrong with multiple safety devices, for sure. Thanks for the support!

Thanks, I appreciate it.

The Eco Worthy boxes are fine and not that expensive. But the Midnite Solar and other boxes are just silly when you get something like this for a fraction of the cost.

Good idea!

The solar panels have diodes.

@@LDSreliance The solar panels only have bypass diodes. They almost never have reverse blocking diodes. There are videos about the difference, and it is explained why you may want blocking diodes in a combiner box.

Yes, I can see where that might be a good thing to add. Thanks

I also noticed there is no lightning protection spd or ground bump, and 48VDC is nearly useless for any serious solar power system.

Thanks! I appreciate it.

You don't get all the benefit of the combiner box unless you do the latter. I would not use the Y connector at all unless you have to. I'd probably run 3 strings of 2s if it were me but I don't know what your roof looks like or what you are trying to accomplish. But having each panel or each small string able to be individually fused using thick gauge cables is the big benefit here.

You definitely want the wire run as short as possible. However, it is less of an issue when you are dealing with higher voltages. So if you have > 48V coming from the combiner box then you are probably fine. But to answer your question, there are quite a few wire size charts and calculators out there. My favorite tools can be found in this video I did in the past: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-TO_a619bWh0.html

Yes, that would be too much. They are only rated for 48V DC. You would need a more application-specific combiner box that can handle that high of voltage.

@@LDSreliance Thank you very much for the response.

You are welcome. Thanks for watching!

Good idea. Thanks

Not necessarily. They both do the same thing (combine several incoming wires into one output wire).

In that case you don't want to use a QO breaker system. These are just the only DC rated ones you will find in stock at your hardware store. There are much higher voltage, solar-specific units you can get. Try Eaton as they have a ton of them up to 500V DC and a ton of Amps if you need it: www.eaton.com/ecm/idcplg%3FIdcService%3DGET_FILE%26allowInterrupt%3D1%26RevisionSelectionMethod%3DLatestReleased%26Rendition%3DPrimary%26dDocName%3DCA08100018E

Maybe you should wire them in parallel to increase your amps instead of volts!

I don't think you really need a combiner box for 4 panels. You can wire them all in series for a 48V array or you can wire them all in parallel with MC4 Y Connector cables. A combiner box is more for complicated series-parallel wiring or for multiple string situations.

No, I have never used one in an AC configuration.

I can't see your pic. It is too small. You don't need a combiner box. But I don't see how you are getting 10 panels down to a single wire with only one 5 to 1 y adapter. You would need two for the positive side and then two for the negative side and then a 2 to 1 adapter on each side to tie the first two together on each side.

@@LDSreliance One for the Pos and one for the Neg. I have them series/parallel connected to make a 24V array. The pic shows me holding a trophy for the Ward Chili cook off.

Haha awesome! I won that one year. OK, that makes more sense if you did 24V.

Yes, in some cases it is wise to put in a diode to block backfeeding the panels. Are you sure the battery voltage is 52V? I assume it is a 48v nominal lithium battery? Do you have a clamp meter you can clamp on and see if any current is passing through?

He is using DC breakers from what I saw, didn't understand the comment

I have been looking for a similar device for almost 12 years. Not that works exactly as you have described (that I know of). There are various devices that can accomplish the same thing, but not as elegantly, simply, or cheaply.

Sorry, I don't mess with AC much so I don't know how you would set that up.

@@LDSreliance thanks for the reply

That is an interesting concept, but I don't see what the real benefit would be of that. You would basically just be putting on a breaker/switch on both the positive and negative leads. How is that better than one?

@@LDSreliance it’s for safety in case there is a short or overcurrent on either leg it will fully isolate that device vs just cutting one side such as just the positive side, but yet leaving the negative lead energized to the rest of the connections. It is just good practice when dealing with DC that both legs are removed from the circuit if a short or overcurrent is detected.

So why is that not done in other applications? In the auto industry or landscape lighting or other low voltage DC applications? I've never heard of this being a best practice or being done (to fuse or breaker both negative and positive). I'm sure it can't hurt anything. I am just curious.

@@LDSreliance at 50v and up it can kill you. 12 & 24v applications your resistance is high enough if u touch something that is energized u won’t get electrocuted. At 48v and up u don’t have enough resistance and it could be fatal if some leg is energized and you complete a circuit. Best to cut the circuit at both connections, especially since there is no equipment ground that is bonded at the neutral as in the AC configuration which should be the least resistance path, assuming all is operation to specs. But what do I know I check 9v batteries with my tongue, so my answers are probably years of shocking my brain cells causing ridiculous conclusions.

You can never be too careful, for sure.

No, that would not work in parallel. To wire something in parallel would mean the voltage is the same.

Why do you need diodes? The solar panels already have them so power can't go that direction.

Incorrect. You need blocking diodes which are different than bypass diodes in the panels when running in parallel. One parallel array can use energy to put current into the other due to shaded or bad panels. Blocking diodes are needed when arrays are in parallel. It’s best to use a real pv combiner box which utilizes fuses for each array and blocking diodes.

Devo is correct. Blocking diodes and bypasss diodes are not the sam thing. There are videos about this on RU-vid. The panels have bypass diodes. But they usually (or maybe always) don’t have blocking diodes. I’m an electrical engineer and have lab equipment, so I was able to check my panels. As expected, they have bypass diodes, but don’t have blocking diodes. Fortunately, it’s easy to buy inline blocking diodes on Amazon.

Combiner boxes are always parallel. They aren't needed for series wiring because you just connect the panels to each other in that case. In your example, the output would be 23V and whatever the output current is for each panel multiplied by 3. So it is the opposite as series wiring, which multiplies the voltage.

@@LDSreliance thanks for the info,a combiner box is not for me. I guess there is no way to run series without the shade affecting the whole string?

Instead of typing out a ton of information here, here is a link to some ideas that may help you: aurorasolar.com/blog/shading-losses-in-pv-systems-and-techniques-to-mitigate-them/#:~:text=How%20to%20reduce%20shading%20losses,level%20power%20electronics%20(MLPEs).

You can do it that way, yes. You could have 6 breakers - one for each panel. Or 3 breakers - one for each string of 2 panels in series. Or 2 breakers - one for each string of 3 panels in series. However you want to set it up for the best performance.

@@LDSrelianceYou think would be ok if I connect them in parallel even though will get some shade for a short period of time? thanks for your info!

If you can't get around the shade then yeah it will be ok. In that case, not having strings is preferable because shade will affect an entire string's production even if the shade is on a single panel.

@@LDSrelianceYOU ROCK THANKS AGAIN!!

You are welcome. Good luck!

The input wires come from the panels or from strings of panels. They get wired to the breakers. Then a single set of larger diameter wires will output the combiner box and head over to your charge controller or grid-tied inverter.

In general that is true. But these aren't normal AC breakers. One of the largest power center companies in the world rates them for 48V DC as well. So I think it is safe to say they will work just fine if you use them within the parameters that Schneider publishes.

Yep!

@ OZ Turks - Lowe's does sell Square D "QO" or "QOB" AC rated breakers - that also have a 48 Volt *MAX* DC rating. But, most 48 Volt battery banks can be HIGHER than 48 Volts, therefore they should *NOT* be used with 48 Volt or higher battery banks, nor used with with 48 Volt VOC or higher Solar Panel Arrays. And it must be a 15 amp - 70 amp breaker. Per footnote #2 - The 10 Amp breakers do not have any DC rating. Download and read the SPECS carefully! This information has be available for about 20 years ...

@@vtorsi610 so what your saying is build a 24 volt system

@@mteca5093 Yes, the QO series breaker will work with a 12 volt or 24 Volt system.

That may be true of most, but the QO is rated for DC and successfully sold and used as a DC breaker by numerous online solar outlets and off gridders around the world. Here is one example of a major solar e-commerce store selling them: www.altestore.com/store/enclosures-electrical-safety/overcurrent-devices-fuses-breakers/din-rail-circuit-breakers/square-d-plug-in-circuit-breakers-p41287/ If a major corporation like Schneider Electric is willing to stamp their approval on these to work with 48V DC then you can bet they are confident they will work. Because if they don't and some cabins or outbuildings catch fire or someone gets hurt or killed, they can lose millions in lawsuits. So they don't mess around with ratings.

I made the comment about using ac breakers for dc current not talking about the panel people tend to believe because it works it can be use and thats not the case ,ac and dc breakers work very different

OK, I thought you meant the QO breakers. Because they work for both. But you are right, if you grab any AC breaker off the shelf, it probably won't work for an equivalent DC current.

What do you mean parallel wiring aside? Each circuit breaker can handle a string of panels. In your case, parallel wiring would be required to use more than one panel on each breaker. It can be done. You just have to work within the safe current carrying capacity of the cables, which is generally AWG #10.

@@LDSreliance so say I wore 2 panels in parallel for a total of 18 amps. I would have to get a 20 amp breaker for those 2 panels?

Yes.

@@LDSreliance so you’re using 4 strings on your setup? The 4 strings come together in parallel?

I don't have a system using a combiner box right now. But in the past, yes.

How do you figure? Even the largest panels, around 400W, could make use of #10 AWG wire for up to 8 feet by themselves @ 12V with less than 2% voltage drop. But anyone using that size of panels is installing a larger system where you will be using much higher voltages than 12V, in which case #10AWG can go for much longer runs.

Sorry I didn't read the word "parallel" the first time before I commented. Yes, you are right. You would not be able to parallel large panels. But I don't know why you would do that, anyway.

@@LDSreliancei need amps more then i need volts. im attempting to run a 5000btu ac on 4 210watt panels in parallel . i think on a good sunny day ill be able to run the a/c without putting much drain on my battery . the ac has a low start up wattage and and draws 40-45ish amps dc the batteries can handle it but only for a 4 or so hours.system dosnt need to run much else Just a few lights and charging little devices. also space is factor cause the panels are on my van roof. other wise id parallel a bunch of little guys and make it easy on myself

@@mastershake1187 But why? High amps gives you no benefits. Your batteries have less capacity (Peukert Effect), you have to run heavy gauge wires (like you mentioned), and it can be more dangerous. Just by running 2 parallel strings of 2 panels in a 24V configuration solves all your problems.

@@LDSreliance the panels im looking at are rated at 12.5 amps so if i parallel 2 strings dosnt that only give me 25 amps? i figure if i can provide all the amps the a/c needs then i dont have to drain my batts down constantly if i parallel all the panels together . according to the specs sheet my 200 ah batts can handle that many amps being drawn from them, but yes it does effectivly turn them into 160ah batteries. is there some other way i can get the a/c running(on a good day) without killing my batteries?

Yes. That is all it is rated for.

@@LDSreliance that’s like one 300-350w solar panel no? Is it 48v for each breaker?

Not necessarily. Most off-grid systems are 48V or less. Most rooftop, grid tied systems are much higher voltage.

@@LDSreliance how many wattage is your system? How many strings?

Mine is 24V with 2 strings. Total of about 1000W right now. This is on my shed.

As I stated in the video, the QO series from Schneider Electric is perfectly safe for 48V DC and the QOB series can go up to 125V DC. They will provide overload protection, which is what is needed, and are UL listed for instantaneous tripping (must use multiplier based on AC curve). They can be used on grounded or ungrounded systems. www.se.com/us/en/product-range/7218-dual-rated-ac-dc-circuit-breakers/#overview

Actually, a 48V PV system would reach much higher than 48V. So the highest you would want to run through this would be a 36V nominal setup.

Works for any solar from 12-36V nominal.

Just three of my 300 watt 24v panels in a string can crank out up to 900w 9.7a and 144v dc in the dead of winter. How are those QO 48v dc breakers going to handle that? There not or they are not going to work correctly. You cannot use your combiner box with QO breakers for a high voltage PV combiner... @@LDSreliance

And just one of my panels by itself can crank out 48v dc in the winter.

I said 12V to 36V DC nominal. If you are going to string your panels above 36V then that would not apply. Very few off grid installs use high voltage strings like you are doing. Most systems are on RV's, boats, gates, surveillance cameras, landscape lighting, and cabins where high voltage would be impractical or impossible. So for most off grid systems, a combiner like this box works perfect.

What are you talking about? The QO series IS rated for DC current up to 48V. Did you watch the whole video or just look at the thumbnail? SPD's are not required for solar panel systems. While it may be a good idea, there are no codes that require it. NEC article 690 covering photovoltaic systems does not even use the word surge in the entire document. So, again, it is a good idea if you live in a lightning-prone area, but it is not "needed" as you stated.

Even though some of what you say MIGHT be true, it doesn't account for those of us who don't give 2 shits about "codes", and feel no compulsion to comply with government mandates that we had no say in.

@@wileecoyote4116 , to ignore the fact that the system is unsafe is just stupid. Whether regulations or not. DC will kill you. I have been an installer for 20 years. In the end it makes it unsafe to work with, or can/ wil damage your own equipment. Here in SA we have a lot of thunderstorms, and our regulations is quite clear. And i always add more protection that what is needed, have you been on a tin roof with PV panels that was not grounded?

I think we can all agree that grounding an AC system is mandatory and the right thing to do for safety. Where we have gotten off the rails a bit is your attack on the QO series load centers that they are not rated for DC (false) and your assertion that you "need" a surge protection device for lightning. I think that is good practice in lighting prone areas, but there are no codes or other safety regulations requiring it and I would sleep like a baby in a house without one. And while you seem very competent with grid tied PV systems where there are lots of rules for cogeneration, grid connection, and all applicable NEC codes for the AC side of things... off grid systems (low voltage DC) are a different animal entirely that you don't seem to understand and have very, very few codes and rules. So lets leave the discussion there and agree to disagree.

For grid tied solar, that is true. But this isn't for grid tied solar. This is for off-grid systems, which are at least as common as grid tied, albeit usually much smaller.

Probably true for grid-tied. But there are no electrical codes for low voltage, off-grid systems to my knowledge.

Illegal? You mean against the NEC or other code? Possibly, although I have seen it plenty of times on AC systems. But this is a low voltage DC system and the NEC doesn't apply.

Most off grid systems are 12V or 24V. Most "substantial" systems are grid tied and don't use combiner boxes.

@@LDSreliance eh, not to throw any shade, but i respectfully disagree - *MOST* "off-grid" systems would be 48V nominal. i'm not talking about your cabin or RV/van 'off-grid' types. i'm talking whole house off-grid. i would speculate +75% would be 48V systems. higher volts = less amps = better efficiency = less $ in wire = longer wire runs, etc.

You are citing a maximum, not the minimum. There are hundreds of thousands of low voltage, off-grid solar panel systems out there just in the United States. They power surveillance cameras for construction sites, mobile floodlights for events, outbuildings for rural and semi-rural homeowners, boondocking RV's, wellhouses, automatic gates, and many other uses. And those large MPPT charge controllers are overkill for most of those use cases. They can get by just fine with a cheap PWM or entry level $100 MPPT controller that operates on 12/24V.

@@LDSreliance all renogy and the epever clones (or is it the ooposite?) Go up to 100V for most models, victrons start at 75V, even the renogy pwm amd clones of that model go to 55V. That's a ton of voltage far above the box. And this is an area where so many people just copy paste without having a clue what their doing, so to have no red flag warning is just not a great thing especially with how cheap it is to just get the 200w panel used at the same price of the 50w new...and bigger is always better, until its not. I would also question why go through the trouble of such a low voltage handicap and fusing when you can do 2 larger parallel strings without the fuses and come out with much more power at close to a similar price when you shift the fuse supplies to mppt and panels. But that's purely opinion on the latter.

You clearly aren't going to see past your narrow band of thinking here so let's just agree to disagree. Have a good one.