Safely using MCB (mini circuit breakers) for PV & Bi-Directional Battery Protection

[LifeWAT]

I am interested in safely using MCBs (mini circuit breaker) wherever possible in my solar setup; however after reading all the threads and web search matches I can find on the subject, I would like to clarify the following:

Questions
1. Is there a way to test for polarized vs. non-polarized MCBs with a multi-meter or otherwise? If so, please reply with the steps for the benefit of the community.

2. If a MCB is not magnetic, can we automatically conclude that it is not polarized, and the direction of the flow of current is not important, or are there other factors to consider?

I have a number of MCBs I purchased from AliExpress. The Tomzn (trip curve B) and EARU (trip curve unclear) breakers are magnetized, and the TAIXI 150A (trip curve B) breakers are not magnetic.

My setup includes a Growatt 5000ES hybrid inverter (US version), 16s EVE 280Ah battery with 200A JBD BMS and 5000W solar panel array. In addition to the MCB to battery, I will also be using 200A T-Class Fuses.

My Magnetism Tests On Camera

My Preliminary Conclusion

The TOMZN and EARU breakers are magnetic and therefore probably polarized MCBs, only supporting current flow protection in ONE direction, rather than supporting bi-directional current flow protection. These should be used only for one directional current, such as PV in from the solar panels.

The TAIXI are not magnetic, and therefore probably not polarized MCBs, and can be used for bi-directional current, such as between a battery and and a hybrid inverter device. Please correct me if this is wrong.

I love the clean DIN rail mount option rather than other ugly form factor switching methods, but will not use this setup if it is unsafe. I'm hoping this thread can bring accurate responses and safety to the community at large.


I have recently been in touch with Nanque Electric Store on AliExpress, and they are assuring me that their DZ47-63 series breakers (DC12-120V) and NQCM1-600 series breakers (DC-12-120V) are non-polarized, and support bi-directional current protection from battery to inverter. If this is true, they could be a good options.

From the DZ47-63 product listing

References:

• http://greenforcesolar.com.au/wordp...of-Double-Pole-DC-Breakers-LVL2-131210-v2.pdf
• https://www.altechcorp.com/PDFS/DC wiring_white paper_Altech DC series_0813.pdf

@Charleswgibbs @Phil.g00 @hgg @Hedges @BradCagle @Will Prowse

 

[Quattrohead]

Manufacturers data will tell you what you need to know.
Don't rely on technical information from a salesperson, especially a foreign one.
Do your own research to satisfy yourself and AHJ.
If you need to get a permit most of these units are no good to you.

 

[LifeWAT]

Manufacturers data will tell you what you need to know.
Don't rely on technical information from a salesperson, especially a foreign one.
Do your own research to satisfy yourself and AHJ.
If you need to get a permit most of these units are no good to you.

With respect,
1. I do not trust manufactures data when purchasing from overseas. In this case I wish to confirm proper operation myself by physically testing.
2. If I trusted the salesperson I wouldn't be here. I made this post because I don't trust the salesperson, and am looking for practical insight from those who have physically tested and understand MCBs, and can provide clarity for the rest of us to do our own testing.
3. I have been researching this topic for days, and have spent extensive hours learning about the subject. If you know the answers to my questions, please post them, or links online where the answer has been given. I'd be very grateful!
4. There are no permits where I live.

 

[BradCagle]

If they are polarized they should have + and - markings on the terminals. They will/should have arc extinguishing mechanism for PV level voltage (just dont exceed the max dc voltage rating)

Right, the non-polarized would be used with your battery, inverter, etc.. since arc is minimal at that lower DC voltage.

 

[Charleswgibbs]

Wish I could help! Im not sure of how to test for polarization, the magnet test would make sense but I don't know if it's conclusive. The presence of "+" and "-" on supposedly non polarized breakers is confusing as you noted.

I would only trust what the manufacture says, and from a manufacture who can be held responsible for inaccurate specs. Midnite breakers are made by cbi but I trust that Midnite wouldn't risk their reputation or liability by mislabeling polarized breakers, so the extra cost is worth the peace of mind to me.

Hopefully the experts will be able to chime in with more info.

 

[meetyg]

I also got some125A and 160A TAIXI MCCBs from Aliexpress. They are not magnetized from my research.
Seller also said its OK to connect loads at the top, even though they diagram shows otherwise.
But because of the diagram and positive/negative symbols, I was reluctant to use them (wasted money).
In the end I went for this as my main breaker, since it says specificly that it NOT polarized:

https://www.amazon.com/gp/aw/d/B09JS22RJC?psc=1&ref=ppx_pop_mob_b_asin_title

Yes, it more costly than the TAIXI breakers, but I wanted to be safe. Also, the size if this breaker is HUGE ! Even larger than the 160A TAIXI breaker, which at the time I thought is pretty large.
Seems like quality stuff.
I guess I will save my TAIXI for workbench testing purposes, or for uses which are only in one direction.

Another option is this one:

ZJ BENY Bdm 125A Dc Circuit Breaker

NOARK DIN MOUNT MINIATURE CIRCUIT BREAKER EX9BN

www.springers.com.au

Under specifications it says: No polarity.
Unfortunately I was only able to get it from an Aussy supplier who agreed to ship to Middle-East. Shipping cost me a fortune, but maybe you will be able to find this model with local (or cheaper) shipping rates.
I plan to use the 125A ZJBENY as my battery breaker (one for each 24v battery) so that I can isolate one battery if it needs maintenance etc... while the other battery continues to power my inverter.

 

[Hedges]

I would think that for a DC rated breaker, magnet and polarized go hand in hand.
The DC47, I think I see 6k amp interrupting for 100A model, 4k amp interrupting for 63A model.
That's in the short circuit current range of lead-acid, not lithium. Maybe class T fuse in series will prevent catastrophic failure. But it isn't "current limiting", will likely leave breaker ruined.

"DC MCB 12V 24V 48V 60V 110V" "DC 12V ~ 120V" I'm going to guess 120V, 110V, and maybe 60V, requires two poles in series.

If you're going to take a chance with one of these, maybe test by loading to rated voltage and over-current so it trips, in both polarities?
(Are they spec'd to function many times, like UL listed breakers are?)

 

[Henderson]

I am interested in safely using MCBs (mini circuit breaker) wherever possible in my solar setup; however after reading all the threads and web search matches I can find on the subject, I would like to clarify the following:

Questions
1. Is there a way to test for polarized vs. non-polarized MCBs with a multi-meter or otherwise? If so, please reply with the steps for the benefit of the community.

2. If a MCB is not magnetic, can we automatically conclude that it is not polarized, and the direction of the flow of current is not important, or are there other factors to consider?

I have a number of MCBs I purchased from AliExpress. The Tomzn (trip curve B) and EARU (trip curve unclear) breakers are magnetized, and the TAIXI 150A (trip curve B) breakers are not magnetic.

My setup includes a Growatt 5000ES hybrid inverter (US version), 16s EVE 280Ah battery with 200A JBD BMS and 5000W solar panel array. In addition to the MCB to battery, I will also be using 200A T-Class Fuses.

My Magnetism Tests On Camera

My Preliminary Conclusion

The TOMZN and EARU breakers are magnetic and therefore probably polarized MCBs, only supporting current flow protection in ONE direction, rather than supporting bi-directional current flow protection. These should be used only for one directional current, such as PV in from the solar panels.

The TAIXI are not magnetic, and therefore probably not polarized MCBs, and can be used for bi-directional current, such as between a battery and and a hybrid inverter device. Please correct me if this is wrong.

I love the clean DIN rail mount option rather than other ugly form factor switching methods, but will not use this setup if it is unsafe. I'm hoping this thread can bring accurate responses and safety to the community at large.


I have recently been in touch with Nanque Electric Store on AliExpress, and they are assuring me that their DZ47-63 series breakers (DC12-120V) and NQCM1-600 series breakers (DC-12-120V) are non-polarized, and support bi-directional current protection from battery to inverter. If this is true, they could be a good options.

From the DZ47-63 product listing

References:

• http://greenforcesolar.com.au/wordp...of-Double-Pole-DC-Breakers-LVL2-131210-v2.pdf
• https://www.altechcorp.com/PDFS/DC wiring_white paper_Altech DC series_0813.pdf

@Charleswgibbs @Phil.g00 @hgg @Hedges @BradCagle @Will Prowse

This is very interesting. I asked them the same thing a few hours ago concerning current protection in either direction for the 150A model and was told it would only protect in a single direction. I may still use them however. For my setup, I'm only relying on the breaker as a disconnect switch for the battery. I'm using t class fuses on each battery and my reliance is on the fuse, in addition to having the BMS and inverters with the necessary over current protection settings.

 

[100FUEGOS]

This is very interesting. I asked them the same thing a few hours ago concerning current protection in either direction for the 150A model and was told it would only protect in a single direction. I may still use them however. For my setup, I'm only relying on the breaker as a disconnect switch for the battery. I'm using t class fuses on each battery and my reliance is on the fuse, in addition to having the BMS and inverters with the necessary over current protection settings.

One day you will open that MCB under some load (it does not have to be huge) and fireworks will start. In this case, that inline fuse will not protect you as the AMPS will not be massive either.

 

[LifeWAT]

One day you will open that MCB under some load (it does not have to be huge) and fireworks will start. In this case, that inline fuse will not protect you as the AMPS will not be massive either.

Could you please explain why so we can learn? If the breaker is indeed non-polarized, and does not direct the arc with magnets in one direction only, why would there be fireworks? I genuinely would like to know.

I also want to clarify that the TAIXI 150A breakers in my original post are the only ones that I presume to be non-polarized, and that might be an option for a battery disconnect switch and breaker function. The other two brands I know can only be used for current protection in one direction.

 

[Henderson]

Could you please explain why so we can learn? If the breaker is indeed non-polarized, and does not direct the arc with magnets in one direction only, why would there be fireworks? I genuinely would like to know.

I also want to clarify that the TAIXI 150A breakers in my original post are the only ones that I presume to be non-polarized, and that might be an option for a battery disconnect switch and breaker function. The other two brands I know can only be used for current protection in one direction.

Was actually going to ask the same question ecspecially when I see the big brand server rack batteries using similar breakers that one would get on amazon and aliexpress.

 

[OilCan]

I personally don't care to use the mini breakers for high current through the battery system, so I installed a molded-base DC circuit breaker from the battery bank. Like this one, it is wall-mounted:

https://www.amazon.com/gp/product/B09P4QNMRY/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

 

[Henderson]

I personally don't care to use the mini breakers for high current through the battery system, so I installed a molded-base DC circuit breaker from the battery bank. Like this one, it is wall-mounted:

https://www.amazon.com/gp/product/B09P4QNMRY/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

Yes, those are quite heavy duty. I have a 600A model as my main total battery DC connect. Looking at the smaller breakers for the individual batteries.

 

[nvbt]

Hi. I am also looking for non-polarized breaker. Just found Projoy PEBS series.
They specially emphasize that it is non-polarized in video on website, also this is stated in datasheet in cnnection diagram.
datasheet for 125A low voltage version https://en.projoy-electric.com/static/upload/file/20221103/1667468510198525.pdf
I'll try to contact their Alibaba store.

 

[LifeWAT]

I would think that for a DC rated breaker, magnet and polarized go hand in hand.
The DC47, I think I see 6k amp interrupting for 100A model, 4k amp interrupting for 63A model.
That's in the short circuit current range of lead-acid, not lithium. Maybe class T fuse in series will prevent catastrophic failure. But it isn't "current limiting", will likely leave breaker ruined.

"DC MCB 12V 24V 48V 60V 110V" "DC 12V ~ 120V" I'm going to guess 120V, 110V, and maybe 60V, requires two poles in series.

If you're going to take a chance with one of these, maybe test by loading to rated voltage and over-current so it trips, in both polarities?
(Are they spec'd to function many times, like UL listed breakers are?)

I ended up ordering two of the larger MCCB (Moulded Case Circuit Breakers). I will test to the best of my ability upon arrival, but I don't think I have a way to test more than about 120A load.

1. TAIXI DC12V 24V 48V 250A Moulded Case Circuit Breaker Battery 100A 200A 300A 400A 600A MCCB Car Charging Pile Protector
I got the 2 Pole, 200A version

2. TOMZN 2P DC 600V DC Solar Molded Case Circuit Breaker MCCB Overload Protection Switch Protector for Solar Photovoltaic PV
I got the 2 Pole, 250A version

Once again, my desire is to use one of these circuit breakers between my 280Ah battery and my Growatt 5000ES inverter, as well as a 200A class T fuse. I appreciate @Hedges pointing out the low "amp interrupting" capacity on the smaller MCBs.

In light of this, I think the MCCB would be the only path I will consider at this point. The MCCB switches that are on the way have 25kA (TAIXI) breaking capacity and 35kA (TOMZN) breaking capacity, vs the smaller 6kA (TAIXI) 150A MCBs in my original post. Please feel free to chime in, but I believe 25kA + should be fully adequate to handle breaking current for my 16, 280Ah lithium cells in series (48v nominal).

The TAXI MCCB I ordered says it has an electrical life of 4000 times (switching on and off).
The TOMZN MCCB I ordered does not have this spec listed. I would assume it to be similar.

I plan to get a thermal camera, to monitor these breakers under load, to ensure they are not getting hot inside with normal load, which in my case will be around 60-110A.

 

[Hedges]

While not as convenient (have to move around to find hottest spot), this is 10% the price:

12:1 Infrared Laser Thermometer

Amazing deals on this 12:1 Infrared Laser Thermometer at Harbor Freight. Quality tools & low prices.

www.harborfreight.com

I used it comparing some breakers, identifying which were aged and running hot.
(I also tested trip current with AC load, and used transformer to test at higher currents/lower voltage.)

Testing Magnetic-Hydraulic circuit breakers

I've built myself a circuit breaker tester. I assembled three transformers into a 3-phase wye auto-transformer, and by means of a breaker and cord/plug it can be repurposed into a current multiplier. A breaker connects X1 to H2 and H3, providing 4.7x current boost on X2 paralleled with X3...

diysolarforum.com

 

[Bud Martin]

I just look at the front panel of EG4-48V rack mount battery, it uses AC circuit breaker
CHiNT CB-125A 100A 250V ~ 50Hz. I wonder how they come up with that.
So they use AC breaker in place of NON-Polarized DC circuit breaker?

 

[Quattrohead]

I just look at the front panel of EG4-48V rack mount battery, it uses AC circuit breaker
CHiNT CB-125A 100A 250V ~ 50Hz. I wonder how they come up with that.
So they use AC breaker in place of NON-Polarized DC circuit breaker?
View attachment 120010

Others have said they are rated for DC too but unless it specifically says so on the breaker I do not believe it.

 

[Hedges]

And an extra pole ganged to it. Remote trip, as a controlled shutdown mechanism?

 

[meetyg]

Those breakers on server rack batteries make me uncomfortable. Some use AC breakers (awful), some use DC breakers, but probably polarized (maybe not a problem if only one pole?).