I have been looking for a bi-directional (non-polarized) dc mcb for use with a battery i.e. greater than 100 amps.

So far I have come across only ABB(S80xP) and CBI(several) that seem to manufacture legitimate products that fit the bill.

Of course there are all the chinese ones that claim to be bi-directional but on closer inspection the images always show the +- symbols which to my mind is a dead give away that it is not what it claims.

I recently came across this one DC No-Polarity Miniature Circuit Breaker (200V DC / 125A / B Curve) (2-Pole) (LFP Battery) that meets the visual inspection. The price is however too good to be true.

Can anyone else pass an opinion?

Edit:

I have a theory that the no-polarity is achieved by looking at the wiring diagram on the 4 pole version DC No-Polarity Miniature Circuit Breaker (1000V DC / 20A / C Curve) (4-Pole) (Solar PV)

If one looks at the diagram the left and right pairs are connected in series, this effectively turns the breaker into a 2 pole breaker. Now if one follows the current flow through either leg one will see that each leg has the arc suppressers facing in opposing directions - hence now bi-directional. Similarly if the 2 pole version is wired as a single pole again bi-directional arc suppression is achieved.

This is not an invitation for anyone to go out and implement it, but if anyone feels like doing so if anyone feels so inclined I would suggest still putting a suitably rate fuse in the circuit. There are many examples in the online datasheets of even reputable brands like Noark showing these exact configurations.

Given the price of these breakers as well as the Chinese one's, to me this is a very cost effective way to implement a local regulations compliant small form factor without resorting to the huge NHx fuse switch disconnectors.

Edited January 29, 20242 yr by kjb

Hi @kjb I saw this one, not sure if this is what you looking for, this item is rather big.

 

https://www.robotics.org.za/XM1-250PV-2P?search=mccb

Edited January 29, 20242 yr by Greglsh

Hi Gregish,

 Yes I have seen that in fact I have a virtually identical one running in my home brew inverter trolley that I made to keep me going through load shedding until I get to a full house system. Of course as you say they are rather large and my goal was to see if I could achieve a compliant result in a DIN form factor.

After a bit of research as mentioned in my first post I found that both ABB and CBI produce bi-directional MCB's, however they are both very expensive as well as hard to come by. As a matter of interest certainly one of the ABB bi-directional breakers claimed to have 2 arc suppression chambers (can't find the doc again), the CBI seems to use some other tech to achieve the necessary result. Both of these are available in 125a versions in an MCB form factor.

 

Quote

I have a theory that the no-polarity is achieved by looking at the wiring diagram on the 4 pole version DC No-Polarity Miniature Circuit Breaker (1000V DC / 20A / C Curve) (4-Pole) (Solar PV)

If one looks at the diagram the left and right pairs are connected in series, this effectively turns the breaker into a 2 pole breaker. Now if one follows the current flow through either leg one will see that each leg has the arc suppressers facing in opposing directions - hence now bi-directional. Similarly if the 2 pole version is wired as a single pole again bi-directional arc suppression is achieved.

This is not an invitation for anyone to go out and implement it, but if anyone feels like doing so if anyone feels so inclined I would suggest still putting a suitably rate fuse in the circuit. There are many examples in the online datasheets of even reputable brands like Noark showing these exact configurations.

Given the price of these breakers as well as the Chinese one's, to me this is a very cost effective way to implement a local regulations compliant small form factor without resorting to the huge NHx fuse switch disconnectors.

Quoting my own post:

I have to withdraw the above whilst it may work in practice (making a non-polarized breaker from a 2-pole polarized breaker). It has 1 fatal flaw - the pole that has the current flowing in the wrong direction will be subject to a momentary arc before the correctly oriented pole disconnects the entire circuit. this would eventually result in premature ageing of the contacts and could in a worst case scenario result in the contacts welding closed. The user would not be aware of the welding closed case and reset the breaker resulting in a catastrophic failure the next time the welded pole was called upon to protect the circuit.

Don't do it! 

Too much thinking aloud here.🤪

Edited January 30, 20242 yr by kjb
Added diagram for clarity

In case it helps anyone else that want's a fuse free installation in a small form factor as well as being cheaper and more readily available than the ABB or CBI alternatives - 

Hager HLFxxxS series MCB's will do the job. They are not polarity marked and I did confirm with EloctroMechanica that this is indeed the case: - relevant page from the Hager catalogue below.

 

They are not cheap compared to the fuse switch disconnect solution or taking the risk with some Chinese MCB with dubious credentials and little to no information available.

Cheapest I have found so far - Online Electrical

Edited January 30, 20242 yr by kjb

On 2024/01/29 at 11:35 AM, kjb said:

Hi Gregish,

 Yes I have seen that in fact I have a virtually identical one running in my home brew inverter trolley that I made to keep me going through load shedding until I get to a full house system. Of course as you say they are rather large and my goal was to see if I could achieve a compliant result in a DIN form factor.

After a bit of research as mentioned in my first post I found that both ABB and CBI produce bi-directional MCB's, however they are both very expensive as well as hard to come by. As a matter of interest certainly one of the ABB bi-directional breakers claimed to have 2 arc suppression chambers (can't find the doc again), the CBI seems to use some other tech to achieve the necessary result. Both of these are available in 125a versions in an MCB form factor.

 

I wanted to ask you on your MCCB is it very difficult to switch the switch, mine I have not connected it yet, so not sure if it requires to be connected, but I am unable to turn the switch from on to off. Currently it seems to be in the on position but I can push it down to off. I did email the suppliers and they said "This is a 250 amp breaker so will need some force to switch" I have my doubts.

 

EDIT: Okay so I tried it again and this time I really pressed hard and it did switch so it does take quite a bit of force to switch from on to off.

Edited January 31, 20242 yr by Greglsh

Yes it does require a considerable effort to turn on or off.

 

On 2024/01/29 at 11:35 AM, kjb said:

Hi Gregish,

 Yes I have seen that in fact I have a virtually identical one running in my home brew inverter trolley that I made to keep me going through load shedding until I get to a full house system. Of course as you say they are rather large and my goal was to see if I could achieve a compliant result in a DIN form factor.

After a bit of research as mentioned in my first post I found that both ABB and CBI produce bi-directional MCB's, however they are both very expensive as well as hard to come by. As a matter of interest certainly one of the ABB bi-directional breakers claimed to have 2 arc suppression chambers (can't find the doc again), the CBI seems to use some other tech to achieve the necessary result. Both of these are available in 125a versions in an MCB form factor.

 

@kjbI wanted to ask you if this DC breaker has a positive and negative side? I am guessing that the switch side might need to turn off the positive but would like confirmation. If it can go either way then that would help, just need to match bottom and top polarity? Also I want to use this in a DIY battery so is this MCCB bi-directional, can the inverter charge the battery back through this or not?

Edited February 3, 20242 yr by Greglsh

I have bought this DC MCCB and wanted to ask,it has a line and a load side but I wanted to use it as a protection device and an isolator for my DIY battery. What I am worried about is is this bi-directional, can the inverter back feed (charge) the battery from the load side to the line side on this device?

https://www.robotics.org.za/XM1-250PV-2P

EDIT: I found this drawing on another site with this model

 

Edited February 5, 20242 yr by Greglsh