12v MCB

[Biggles]

Hi

 

I have asked this before and the answer seemed to be a resounding yes to Square D MCB's

 

Does anyone know of any other makes that will work with 12v DC?

 

I have no objection to using Squared D MCB's in fact they do a very good range but their consumer units aren't to my liking. Will they fit in to a Wylex CU? I know all this stuff is supposed to be DIN but is it really?

 

Biggles

[P R]

Dont know much about which MCB's are ok for 12v most AC ones can suffer DC arc if used on 12v. But most AC MCB's are DIN but the hight and position of the conections wont allways match the buzz bar if different makes are used

[Robin2]

I suspect that all domestic 240v mcb's work at 12v. Certainly Proteus ones do - see technical spec here

 

 

A few years ago I got a 100A mcb for another boat - I think it was made by Siemens - and similarly it worked at 12v.

Edited December 24, 2010 by Robin2

[Guest]

Unless things have changed since I quit the trade, Square D MCB's should fit other CU's.They were built to standard dimensions, but of course things change..

 

I suspect that all domestic 240v mcb's work at 12v. Certainly Proteus ones do - see technical spec here

 

 

A few years ago I got a 100A mcb for another boat - I think it was made by Siemens - and similarly it worked at 12v.

I suspect you are right about them all working at 12V dc,it is probably just that they haven't been tested at this voltage.

Edited December 24, 2010 by Guest

[Tony Brooks]

I suspect that all domestic 240v mcb's work at 12v. Certainly Proteus ones do - see technical spec here

 

 

A few years ago I got a 100A mcb for another boat - I think it was made by Siemens - and similarly it worked at 12v.

 

They will all "work" on 12v DC but unless they are rated for DC there may well be contact trouble or even welding - as has been already mentioned.

 

The link ones will certainly work because they are DC rated but I reiterate what has already been said. If you insist on using AC only rated mcbs then you may be asking for problems and the last thing I would want is the contact welding under fault current, or even burning/pitting and then sticking.

Edited December 24, 2010 by Tony Brooks

[Guest]

They will all "work" on 12v DC but unless they are rated for DC there may well be contact trouble or even welding - as has been already mentioned.

 

The link ones will certainly work because they are DC rated but I reiterate what has already been said. If you insist on using AC only rated mcbs then you may be asking for problems and the last thing I would want is the contact welding under fault current, or even burning/pitting and then sticking.

Yes it is imperative that this is checked out with the manufacturer first. There are several that are tested at 12V dc: Someone once compiled a list on here but I can't find it.

I have said this before but I once picked up a panel in a chandlers designed for 12 V dc boat systems, and the switches were marked "ac only."

[Robin2]

They will all "work" on 12v DC but unless they are rated for DC there may well be contact trouble or even welding - as has been already mentioned.

 

The link ones will certainly work because they are DC rated but I reiterate what has already been said. If you insist on using AC only rated mcbs then you may be asking for problems and the last thing I would want is the contact welding under fault current, or even burning/pitting and then sticking.

 

I would not use them without seeing in the specification that they are DC rated.

 

The only ones I enquired about could be used in DC circuits. Have you identified any makes that are only AC rated?

[Guest]

I would not use them without seeing in the specification that they are DC rated.

 

The only ones I enquired about could be used in DC circuits. Have you identified any makes that are only AC rated?

I believe MK MCB's are rated at AC only, but stand to be corrected.

[Chalky]

They will all "work" on 12v DC but unless they are rated for DC there may well be contact trouble or even welding - as has been already mentioned.

 

The link ones will certainly work because they are DC rated but I reiterate what has already been said. If you insist on using AC only rated mcbs then you may be asking for problems and the last thing I would want is the contact welding under fault current, or even burning/pitting and then sticking.

This is also a problem with relays. As the contacts separate they strike an arc which locally melts part of the contact surface. The "helpful" freewheel diode and the collapsing magnetic circuit cause the contacts to bounce before they fully separate. (why you should use a resistor in preference (siemens application note)). Most times this bounce will cause material transfer (pitting), eventually it will lead to the contacts welding or hooks forming. The usual fixes are to change the contact material so it doesn't melt, use a resistor instead of a diode, and design the relay so the arc quenches properly.

In an MCB there shouldn't be an issue with material transfer since they aren't switching regularly, the main problem is quenching the arc and for most domestic type MCBs that's related to how far and fast the contacts separate. As Tony says, they'll all work, just some better and more reliably than others. At the end of the day it's all about risk management - what do you feel happy with. In an ideal world (like just won the lottery!) I'd use big IGBTs (large power transistors) to do the switching...

Edited December 24, 2010 by Chalky

[ditchcrawler]

A bit of Googling brings up this

 

ABB DC OK

 

Moeller standard FAZ-type MCB OK for DC

 

Merlin Gerin C60-type are suitable for d.c

[PaulD]

A bit of Googling brings up this

 

ABB DC OK

 

Moeller standard FAZ-type MCB OK for DC

 

Merlin Gerin C60-type are suitable for d.c

 

Another option for us old uns who don't trust MCBs. Newey and Eyre have a DIN rail mounted fuse carrier which takes 10x38mm "French" cartridge fuses. I installed some 4/5 years ago and so far no problems. Part # NLFCFH10.

 

Paul