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48v battery breaker suggestions?

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(@thebutcher)
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I did a little digging, the requirement for a non-polarised ganged breaker here is partly due to the mains risk in transformerless inverters, but also partly because of clown installers using incorrectly wired single polarised breakers causing fires.


   
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(@wpg205)
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Thanks for the thoughts/suggestions.

Anyone have have a suggestion for a polarized or non-polarized 2 pole DC breaker that they trust? I'll have max amps of 60 and volts 100<. I've searched and searched and haven't quite found anything. I need it to be din mounted. 

 


   
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(@thebutcher)
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I'd be happy with a 2 pole TOMZN.  They have a range of options, but here's a 2 pole 80A 600VDC rated one.  If you contact them they can supply the datasheet and wiring arrangements for their breakers.

https://www.aliexpress.com/item/32788927432.html?spm=2114.12010612.8148356.19.29f1a4c5Vrrdda

 


   
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(@thebutcher)
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Well, now not so happy.  The Tomzn breakers do work well but I just discovered something that isn't so good.  For no particular reason I had the box of spare breakers on my bench and idle curiousity got the better of me so I started checking the magnet orientation in them.  1 of them was reversed.  Nice.  Effectively it means that if this breaker was wired with source and drain on the same side as the others, the contacts opened and a persistent arc formed (not always the case) it would be pulled down into the contacts (or pushed into, I don't know the internal layout) instead of being forced into the arc trap and extinguished.  I will be checking all the ones in service later today.

It always pay to test stuff purchased from China, even if it is a reputable brand.


   
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(@sid-genetry-solar)
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Is this a single-pole breaker?  I'm aware that the 2-pole breakers seem to have the polarities reversed between the 2 poles.


   
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(@thebutcher)
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Yes, single pole.  The 2 pole breakers are reversed with the intended wiring to ensure one side is always going to push any arc into the trap and break the circuit.

I'll still use Tomzn breakers, they seem pretty robust, but from now on I will be checking the magnet orientation in singles to ensure its the right way around and in 2 poles to ensure they are opposed orientation.


   
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(@thebutcher)
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I forgot to mention, my use methodology is:

  • if the thing on the far side of the breaker can only ever sink current I am happy to use a single pole breaker
  • If the thing can both source and sink, ie a battery or a charger (defect = draws current), I use a 2 pole breaker since it has to be able to safely break current flows in both directions.

   
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(@thebutcher)
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On 8/21/2021 at 12:26 PM, TheButcher said:

I'll still use Tomzn breakers, they seem pretty robust, but from now on I will be checking the magnet orientation in singles to ensure its the right way around and in 2 poles to ensure they are opposed orientation.

My opinion is changing.  The Tomzn breakers I have are supposedly 125A.  Today I put one to the test.

Standard conditions would have these things tested at 25c air temp but being summer here it's 31c instead.  Not that significant in the scheme of things but even so it has to be considered.  The breaker was in free air, no obstructions on either side nor any other heat sources such as another hot breaker and all cabling / fittings in good stead.  With my inverter chugging along at 2800W AC ouput, meaning DC amps should be around 125A (24V lifepo4, bus voltage was nigh on 25, 90%-ish efficiency in the inverter) and found acceptably close via a DC clamp meter.  The breaker held on for a few minutes then tripped.

Well it's better to have a breaker let go early than late but it should have kept going for a lot longer in ambient 31c, a lot longer.  Unfortunately that's not the end of it.  The breaker, given plenty of time to cool, will not reset.  It's toast.

I think I'll try some TAIXI MCCBs and see how they go.  Stay tuned.


   
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(@sid-genetry-solar)
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23 minutes ago, TheButcher said:

The breaker, given plenty of time to cool, will not reset.  It's toast.

Very interesting.  I've got several of these breakers on the MPPT charge controllers--but all the main power breakers I'm using are non-Chinese units (i.e. Airpax, Heinemann, etc.)  Worth noting that I've even had problems with (used) GJ1P breakers tripping early AND half-tripping (i.e. only one pole tripping, but not both)--context being the 12kw inverter tests at Sean's w/ a 300A GJ1P.

I will be very interested to hear how some "TAIXI" breakers handle.  They're all so similar in design (except for the print) that I can't help but wonder if they're all just rebrands of the same shoddy breaker manufacturer...


   
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(@inphase)
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I know that budget can be a concern, but when it comes to circuit breakers handling any appreciable current, I stick to known quality manufacturers. The ones you would use for line voltage distribution, like Eaton or Schneider/Square D, Siemens, or even, God help me, GE. There are some pretty decent used ones. A large frame enclosed circuit breaker from nearly any manufacturer will have a DC rating. Sometimes you have to use a two or three pole breaker with the poles in series to get that rating, but that, in my opinion, is better than chancing it with a Qong Poo Best Electrics, Ltd. brand breaker.


   
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(@sid-genetry-solar)
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1 hour ago, InPhase said:

A large frame enclosed circuit breaker from nearly any manufacturer will have a DC rating.

Most regular AC breakers are only rated to 32vDC; usually for 48vDC systems, we end up needing dedicated DC-rated breakers. 

 

1 hour ago, InPhase said:

Sometimes you have to use a two or three pole breaker with the poles in series to get that rating, but that, in my opinion, is better than chancing it with a Qong Poo Best Electrics, Ltd. brand breaker.

I understand you're referring to multipole breakers, and ganging the poles in ONE UNIT together in series...but I feel I should clarify in case someone tries putting MULTIPLE breakers in series "to increase the DC voltage rating."  The problem with that is the extreme likelihood that ONE of them will trip first, resulting in that ONE breaker seeing the ENTIRE bus voltage...which it isn't rated for. 

 

I've heard customers complain about name-brand (though used) DC-rated breakers tripping early, so not sure what all is involved with that.

At least I'd rather they trip early...rather than not trip at all.


   
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(@thebutcher)
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Posted by: @sid-genetry-solar
Very interesting. I've got several of these breakers on the MPPT charge controllers--but all the main power breakers I'm using are non-Chinese units (i.e. Airpax, Heinemann, etc.)

I think the problem with these things are the contacts going high resistance, high being in terms of milliohms of course.  I pulled the failed one apart and noticed quite a bit of pitting on the contacts.  In all the time I have had this breaker in service it has not been switched under load and not had the inverter's capacitors dropped onto it either.

I felt the battery side breaker on my Victron charger just now and it was roasting hot indicating it was carrying high current but the Victron was only doing about 30A out at the time.  The meter showed the breaker was dropping 500mV and a bit of probing showed that it had to be the contacts.  Yikes.  Pulled that one out of service and put a spare in which shows about 25mV drop.

I think it'd pay to check the breaker's temperature and voltage drop under load Sid, just in case you have a problem lurking there.


   
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(@inphase)
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7 hours ago, Sid Genetry Solar said:

Most regular AC breakers are only rated to 32vDC; usually for 48vDC systems, we end up needing dedicated DC-rated breakers.

I'm not referring to your standard snap-in type residential circuit breaker. I mean something like this Eaton EHD3100 three pole breaker I have on my desk. It is rated at 250 VDC if two poles are used in series. I would bet that at 48 volts that wouldn't even matter.

7 hours ago, Sid Genetry Solar said:

 

I understand you're referring to multipole breakers, and ganging the poles in ONE UNIT together in series...but I feel I should clarify in case someone tries putting MULTIPLE breakers in series "to increase the DC voltage rating."  The problem with that is the extreme likelihood that ONE of them will trip first, resulting in that ONE breaker seeing the ENTIRE bus voltage...which it isn't rated for. 

 

I've heard customers complain about name-brand (though used) DC-rated breakers tripping early, so not sure what all is involved with that.

At least I'd rather they trip early...rather than not trip at all.

You have to give a used breaker a little bit of a wide berth. There's a reason why it was pulled from service. After a few hard trips, a breaker's calibration is nudged off of nominal, maybe way off. Still workable, but a little quick on the trigger.


   
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(@sid-genetry-solar)
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Posted by: @inphase
You have to give a used breaker a little bit of a wide berth. There's a reason why it was pulled from service. After a few hard trips, a breaker's calibration is nudged off of nominal, maybe way off. Still workable, but a little quick on the trigger.

True, but when the Eaton EHD3100 retails for $535........

...that's why I tend to buy "new old stock" from eBay for about $50/ea 😉.


   
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pilgrimvalley
(@pilgrimvalley)
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I like the class T fuses for the inverter to LiFePO4 battery protection ,,,,, yes I know (a class T fuse) is not a circuit breaker that is resetable....but then again many DC rated breakers are not designed to be shut off switches and are only reliable some of the time. 

the second part: >>>>  is a Square D QO heavy duty disconnect switch which can be bought in varieties of 250volt DC to 600 volt DC ratings....

then if you need to disconnect you just use the proper DC rated disconnect switch.... I have several of these....

and the class T fuse provides the high amperage interrupt needed for LIfePO4 batteries... I have 544 amp and 1088 amp LifePo4 batteries as well as 280amp LifePO4 batteries in service... i do not pull that high amperage but have the heavy duty equipment vs the el cheapo ya never know what you get Chinese copycat stuff

YMMV

some people do not like class T fuses ( or any fuse as it is a one time safety that has to be purchased every time you blow one) as you have to buy another fuse if it blows....but if it blows you have a fault in your wiring set up that you desperately need to find and correct....

your mileage may vary but I use 4/0 copper cables with hydraulically crimped lugs and 300 amp or 400 amp class T fuses...they protect the inverter from the battery and if it is a junk inverter then they protect the battery from the junk inverter...

I have had no problems with class T fuses and heavy duty 250 volt DC rated disconnect switches.....

I have lately been upping the ante to 600 volt rated DC disconnects....

I like Square D brand heavy duty DC rated disconnect switches....you can get them with or without fuses in steel boxes....I normally try to get the outdoor rated DC disconnect boxes; even if I install it inside....

one bad install inside your house using al cheapo stuff >>>> ???? 

I have cleaned up house fires behind rotten tenants >>>> not fun....

spend the time and money >>>> to protect your investment >>>> do your research.....

AC wiring is the easy side IMO

DC wiring takes more care to be safe,,,, be careful in all you do....🤔😎

 

 

 


   
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