What's the difference between 230v circuit breakers and 12v ones

[Artstu]

I want to connect a couple of circuit breakers on the leads from my 12 volt leisure battery, could I use 230 volt ones? is there a difference as I see that the 12 volt ones seem to be about 7 or 8 times the price of 230 volt ones.

thanks

 

[rog_london]

There most certainly is - two important differences, in fact....

(1) The 230 volt ones are not usually designed to deal with huge surges (compared to their trip rating) as the circuits they find themselves in are properly fused further up the line. 12 volt ones expect to find themselves on batteries which might possibly deliver 800 or more amps into a short with no other protection between your breaker and the battery.

(2) Actually this is probably more important than the above: your 12 volt ones are expected to deal with DC supplies while your mains ones deal with AC supplies. Not wishing to overcomplicate things, breaking an AC circuit requires a relatively small gap between contacts, whereas breaking a DC circuit needs a substantial gap, good insulation, and the ability to withstand a flaming arc until the contacts have opened sufficiently.

So - your 12 volt breaker is a much more substantial item than might be needed for 230V, despite the fact that you might think the additional voltage would be the most important thing - it's not: it's the large DC fault currents and the inductance of the circuit which can make an arc persist long enough to do quite a bit of damage.

Rog.

 

[NRG]

As Rog says there are differences between AC and DC types: Chapter Nine - DC Overload Protection | MrSharkey.Com However, there are also types that are rated for both with the voltage de-rated for use in DC circuits. Check the spec sheet for the device you are thinking of using...in reality at the voltages and current levels we use on an E-Bike it probably won't make much difference if you just use an AC breaker.

 

[themutiny]

There most certainly is - two important differences, in fact....

(1) The 230 volt ones are not usually designed to deal with huge surges (compared to their trip rating) as the circuits they find themselves in are properly fused further up the line. 12 volt ones expect to find themselves on batteries which might possibly deliver 800 or more amps into a short with no other protection between your breaker and the battery.

(2) Actually this is probably more important than the above: your 12 volt ones are expected to deal with DC supplies while your mains ones deal with AC supplies. Not wishing to overcomplicate things, breaking an AC circuit requires a relatively small gap between contacts, whereas breaking a DC circuit needs a substantial gap, good insulation, and the ability to withstand a flaming arc until the contacts have opened sufficiently.

So - your 12 volt breaker is a much more substantial item than might be needed for 230V, despite the fact that you might think the additional voltage would be the most important thing - it's not: it's the large DC fault currents and the inductance of the circuit which can make an arc persist long enough to do quite a bit of damage.

Rog.

yemuut el me3allem wala yet3allem!!!

OR

يموت المعلم ولا يتعلم

 

[Alex728]

(2) Actually this is probably more important than the above: your 12 volt ones are expected to deal with DC supplies while your mains ones deal with AC supplies. Not wishing to overcomplicate things, breaking an AC circuit requires a relatively small gap between contacts, whereas breaking a DC circuit needs a substantial gap, good insulation, and the ability to withstand a flaming arc until the contacts have opened sufficiently.

I collect old engineering books from the 1930s to 1950s (when I can find them in the charity shops) and the risk from arcing on (DC) mains circuits is mentioned...

anyone got a source for 24V and 48V circuit breakers? (not just for ebikes, for standby power/renewable energy systems)

 

[Fecn]

CPC sell everything...

Here's the DC rated circuit breakers I found. (Scroll down past the switches)

Your Search Results | CPC

 

[NRG]

Good find and all dual rated...thanks!

 

[NRG]

BTW the CPC DC listed voltage rating is only correct for the single pole breakers. The dual pole ones are rated for 60v DC.

 

[Andrew harvey]

If you go for 240v breakers then they are available in B,C or D types, the D types are motor rated and will withstand the surges best.
A standard circuit breaker, B type, will happily take a load of 1.5 times it's rating, at which current it should trip within 5 seconds or so, with an old fasioned rewireable fuse it was about 5 minutes.

 

[theskip1]

CPC sell everything...

Here's the DC rated circuit breakers I found. (Scroll down past the switches)

Your Search Results | CPC

could somthing like this be used for reverse polarity protection?

 

[Fecn]

You want Diodes for reverse polarity protection. The circuit breakers will only prevent over-current sutiations where you're pulling too many amps.