DC Solar Circuit Breakers in 5 Minutes: How to Choose Breakers, Avoid Future Problems! Quick Guide
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- เผยแพร่เมื่อ 12 ก.พ. 2023
- Here's some of what I've learned about choosing DC PV circuit breakers for my solar power systems over the years. Make sure you choose the correct type of circuit breaker for each use case, for example: PV solar feed, charge controller, inverter.
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Making the effort to get these details right and understand them is time well spent.
There are so many DC 12/24V and solar PV circuit breaker options on the market, it can be hard to distinguish which ones work well and which ones don't. Reading honest reviews and performing a bit of research can save you a lot of trouble in the future.
Watch out for dishonest sellers listing AC circuit breakers as DC PV solar rated.
Using an ohmmeter to check new and existing circuit breakers for high resistance is a good idea. There should be very little resistance across the breaker. Otherwise, the breaker is suspect.
If you are concerned about the resistance of the protective device, consider the following:
The hotter a circuit breaker gets, generally, the greater it's potential resistance and so the lower its efficiency. Believe it or not, a circuit breaker should be kept as cool as possible.
Sometimes it's better to use an appropriate fuse (such as an ANL fuse) instead of a circuit breaker, as they generally have less resistance - although they too should be kept as cool as possible for the same reasons as circuit breakers.
Quality circuit breakers usually have detailed specifications listed, and you should read them before buying.
Avoid cheap circuit breakers that make false claims and/or don't have proper specifications listed.
A circuit breaker can't protect your investment of wiring and equipment if it doesn't work as expected.
Assumptions can be deadly. It's important to do research and ensure you have the right circuit breaker for the job, and that it will really protect the system if there is a fault.
It is important to pick a breaker with the right amperage rating for the application. Too low and the breaker will activate when there is a surge draw under normal operating conditions, for example when an inverter starts an air conditioner. Too high and it won't activate when there is a short circuit or fault, leading to damage and possibly a fire.
Learn to read and understand the labels on the front. Can you tell the difference between AC and DC markings?
This type of circuit breaker is called a mini circuit breaker or MCB. But there are a lot of classes and variations of each type, so it's important to pay attention to the details.
Some circuit breakers are polarized, meaning they have a positive and negative polarity. Be sure to check the markings and specifications to ensure the breaker works correctly.
When installing a circuit breaker, make sure and torque the terminals properly.
Thermal expansion and contraction makes the wires want to move. The breaker will naturally warm up and cool down over the course of normal use. This can cause loose wires, arcing, heat and fire.
Wires should also be clamped down near the breaker so they don't move at all.
Stay away from the cheapest circuit breakers if you really want to protect your system.
Don't cheap out. Saving 10 dollars on a circuit breaker is not worth causing a fire or burning out wires and equipment!
Consider testing a circuit breaker if you're not sure it will work, but only if you have the ability to do the test safely.
Double Pole DC circuit breakers can switch both the positive and negative side of the PV feed simultaneously.
Circuit breakers are riveted together at the factory, and thus cannot be serviced. Genuine high quality DC circuit breakers are so complex inside, reassembling them would be pointless and educational only.
Hope this video helps you out. Thanks for watching!
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Very informative video. Also I recommend to other viewers to read the comments. Potential questions I had were answered as well as questions I had not yet considered. I thank you once more for the effort you put in to making these videos and the insane effort you put into answering every question.
@Ulbre Thanks a lot for the good feedback! you really understand the effort required :) Some videos take months to produce. The 12v oven video was well over a year! I try to keep up with comments as that helps improve video rank (I hope). Thanks for watching and commenting!!
Thank you! Exactly the info I was lookin for. Good luck in your future endeavors.
Glad to hear it :) welcome!!
Super info. Question, as your example; does the langir C15 has polarity? What does the symbols for 1, 3 on top, 2 and 4 at the bottom mean? Thank you.
Hi, glad you liked the video! The langir is not polarized, but it is a DC breaker. The documentation for the model shown indicates the DC source/load can be connected to either side (backfeeding is also acceptable with this type of breaker), or you can loop the wire on the bottom (2,4). One reason for the numbers is to ensure correct identification of the terminals. If you find a breaker with (+/-) labels, it's extremely important to check the installation documents. Current must flow in the correct direction, no matter where the breaker is wired in the circuit. If you do not see polarization markings, then the breaker is supposed to be able to interrupt DC in any direction. I've noticed the manufacturers sometimes take slight liberties with how they label and print their breakers, and it can get very confusing. In short, to install breakers safely it's important to spend time researching and looking up the spec sheets, to avoid making mistakes. If the company's documentation is not clear, I'd buy from another company that has good installation instructions. Hope this helps. DD
Great video. ❤
Thank you! :)
I’m using a DC breaker to isolate my PV array from the SCC. I have the PV array is wired to 1 and 3. The SCC is wired to 2 and 4. Is that correct or does it not matter? TIA.
Just guessing it's a similar breaker to the example? Should be fine, but can you check if your breaker has a datasheet somewhere showing the electrical specifications and hookup diagram. On the double pole (and non polarized) DC breaker shown in the video, it's perfectly fine according to the documentation. If the breaker is polarized, just need to make sure the voltage is flowing in the correct direction.
I have a 2P 16A MCB rated at 500vDC. I will be breaking the (+) and (-) through it. My solar array puts out about 330vDC. When you say it can only handle 250vDC/side, do you mean I need to go to a breaker with a voltage rating higher than what I've got (i.e., 1000vDC)?
Hi, should be fine, as it will break the 330V circuit twice simultaneously - no problem.
@@solarpoweredge 👍 Super, thanks.
Welcome!!
NEED HELP: Understanding DC Circuit Breakers???
1) I have 2 48V battery racks
each with 6 batteries in parallel.
Max Amps IN and OUT is 100A each
so each rack is Max 600A at 48V
but realistically just under 60V
Could you recommend a DC Breaker
that will handle 600A at 60V?
2) Inverters max in and out is 250A
could you recommend a DC breaker
to handle 250A at 60V (for 48V)?
3) solar strings are 450V at 12A
could you recommend DC breaker?
Please help!
Thank you
Hello, for the batteries, you need a very big fuse or circuit breaker (harder to find). I recommend a cylindrical bolt on fuse or a big ANL fuse if you can find it. In this case it should be a brand name from a big company, for example Eaton or Schneider. You could also pair a fuse with a very large DC disconnect switch for battery isolation if needed.
For the inverter, a brand name (Schneider electric) 300A+ (could still use ANL fuse).
For the solar panels, there are many options. A 600V or higher ~20-30A breaker from a brand name - another words, avoid the cheap generic brands. Beware and read the documentation for the breaker - at such high DC voltage mistakes can be very risky.
For such an install, you may need a to consult a qualified electrician to perform an inspection before taking the system live. Hope this helps!
Very informative video on DC breakers. I am using 8 455 watt panels per string, 4 strings total. Each strings OCV is 394 at 14.3A (Isc x 1.25). On the coldest day, voltage will jump to 432VDC. I was thinking 500VDC at 15 amps but I am having a time finding QUALITY breakers for this setup. Could you please check my numbers and inform me of a good supplier of quality DC breakers and their housing? Thank You very much
Hello and thank you for the good feedback on the video; the breaker rating needs to exceed the string current by some margin, it looks like you calculated that already. With such high voltage, I'd suggest brand name breakers only. Double-pole if possible. Quality breakers are harder to find and more expensive. Indeed what you will find absolutely everywhere are the cheaper options, they are easy to find. I recommend searching for old established brands vs. cheap products with low price on large ecommerce sites. I can't put links here. Examples, Eaton and Schneider but there are others. If you spend some time searching, eventually you will see more professional websites selling pro-grade PV items including the breakers. They tend to be smaller more generic sites. It sure does take some digging but about 15 minutes searching should do it :)
@@solarpoweredgeThank You much! I've looked for hours to no avail. I'll check Eaton and the others, I am sure they have DC rated breakers. I would assume they would be magnetic, arc fault types? Should I use polarized types?
So my numbers for the breakers, VDC/A, (500/15) are acceptable? Or should I go up on the amps, say to 20? I just want this thing to be safe and able to shut down automatically should something bad occur.
Thank You for your help, greatly appreciated!
You are welcome... I have found it is very hard to find actual online sellers for decent breakers. There is one company plastered all over the internet, but they don't actually make breakers and so won't mention their name here. For Eaton and Schneider you may have to contact a dealer. Or look for a local PV / electrician supply house that is willing to sell to you. I don't know why they make it so hard! I usually don't find the premium names on the big "A" website for example, except in AC breakers.
I am pretty sure any PV DC circuit breaker from the big names will have satisfactory arc handling characteristics. I wouldn't necessarily spec polarized breakers, but just need to install them correctly if they are polarized. As far as the rating, 400v on a 500v breaker is fine. If your series string current x 1.25 is under 15A (meaning you allowed about +20% margin), that should be fine as well. Keep in mind in cold weather the current might spike. Sun comes out from behind the clouds, hits the freezing panels, current spikes. The worst that could happen? It might trip the breaker, but that's hopefully not going to be a common occurrence. It's not dangerous, just a potential nuisance.
@@solarpoweredge Thank You Sir. That 434 volts is with temp compensation down to 15 deg. F.
Thanks again, the hunt continues...
NP sir, glad I can help, take care :)
55watts 2 panels need breakers?. If yes, how many amps breaker need?
Hello, 550 watts total? What is the current on the panels? Estimate: 24v panels, probably need about 20a PV breaker. 12v panels, probably 40a. Without knowing the full details (voltage, amperage), it's very hard to be sure.
2:00 how to know the correct ampere ?
I have 2 solar panels each one is 545W and max power current 13.36A
I have 10 ampere breaker but it turns off when I use 600W
Hi, the 10A breaker is probably undersized for the panels. There are multiple ways to handle this. One way is to use a 16A breaker for each panel (for parallel connections) or one 16A for series connection. A ~32A breaker could be used for both panels in parallel circuit. Those are very powerful solar panels so I believe you need a bigger breaker. Hope this helps. -DD
@@solarpoweredge thanks
Welcome! :)
Looking for a recommendation for DC, 300 A
Larger DC breakers are harder to find. Check out Schneider Electric DC breakers, expensive but high amp ratings. An alternative is to use a 300A+ ANL fuse block, those are much more cost effective and can still protect the circuit.
HELLO, Can you please guide me . I have 8 panels 410 watts each connected in series with approximately 380 VDC and 15 amp , my question is can i use 16 AMP , 500v dc breaker
Hello, that is very high voltage, must wear gloves and use proper protection.
The amperage rating on a 16A breaker seems too close to 15A. So it might trigger randomly. No harm done, but that would be annoying. I'd recommend at least 20A+ and 500+Vdc.
Possible option - run 2 strings, half voltage, double the conductors, and 2 lower amp breakers would be fine. This also reduces problems from panel shading.
@@solarpoweredge . Thank you for your prompt response. For the time being I have 8 panels in a series , my inverter capacity is till 16 panels so probably I will mount another 8 panels into separate series string . If I divide my current 8 panels into 4 + 4 string in parallel, don't you think my vdc will go way down. Since my inverter minimum vdc input requirement is from 130 vdc to 500 vdc max. I Will follow your suggestion to install a 20 amp breaker .
@@solarpoweredge . Thank you for your prompt response. For the time being I have 8 panels in a series , my inverter capacity is till 16 panels so probably I will mount another 8 panels into separate series string . If I divide my current 8 panels into 4 + 4 string in parallel, don't you think my vdc will go way down. Since my inverter minimum vdc input requirement is from 130 vdc to 500 vdc max. I Will follow your suggestion to install a 20 amp breaker .
@@solarpoweredge . Also please explain a bit about panel shading
. My rooftop doesn't have any obstacles for panel shading . Yet still plz guide if I divide my current panels into 2 strings , how will my inverter perform
Inverter specifications are minimum 130 vdc required and max.500 vdc for PV input
Nice
Thanks :)
Dang, no links?
@DrewAk49 Hello, do you mean for DC breakers? I had to leave the links out out on this one. But if you search "Langir dc solar breaker" on Amazon, you will see at several options. I really like Langir circuit breakers and own several by now.
👍
Ty :)