12 Volt Distribution

[Ecartar]

Does anyone have any experience of using a 240v Domestic Consumer Unit with MCB's as a distribution panel for 12v DC. I have seen these fitted on boats, but on querying the wisdom of this arrangement with a good friend (who has more electrical knowledge than I do) he said the problem may be that 12v DC has the tendency to arc unless contacts are 100%. Presumably the same thought would apply to using 240v domestic switches for lighting, etc?

Thanks,

 

[oldsaltoz]

G’day Ecartar.
Wired up a new S and S for a friend about 6 years ago. We used a standard domestic distribution box with Circuit Breakers; I seem to recall the breakers we used were the type that switch very fast and have a wider gap than standard (rating #6 I think). All terminations were treated to reduce electrolysis and tinned wire was used throughout. As I said that was 6 years ago and not so much as a blown globe to date, seems to work ok and saved plenty.
DC tends to ark when switched and this burns out the contacts; this is not a problem with AC.

 

[Guest]

I have used good quality domestic distribution boxes for many years on many boats for both 12 &24 volt DC installations without any problems whatsoever. Most of these installations have been for inland boats so the question of corrosion may arise in a salty environment but I suspect that domestic boxes will still give more than adequate service relative to cost. Same aplies to switches, sockets etc.

 

[VMALLOWS]

There is nothing wrong with using a domestic consumer unit as the 'wiring centre'. However the switch and/or MCBs need to be suitable for the DC current involved. You can certainly fit the appropriate DC MCBs. In general a switch suitable for a given AC current will have a very much lower DC rating due to the arcing which occures with DC when you break the circuit. Typically, a switch rated as 10amp/230v might have a rating of 1amp/12v. Both ratings are commonly marked (or given in the catalogue specification) for toggle switches and the like. Depending on the type (thermal or magnetic) MCBs may have different trip characteristics when used on AC or DC ... or may not be suitable at all.

Domestic switches are not expected to be used on DC so a DC rating is not normally specified. Even with a load of only say 10w DC I would expect a short life from a typical lighting switch. (The break is very slow. You need a fast 'snap' action with adequate contact separation).

 

[ean_p]

Have been down this road and mcb by 'Merlin Gerin' are ok for use on dc......so say their tech people, other brands may also be good.....call them and ask ....it may well save you a small fortune....

p.s. you don't really need the consumer unit, just a length of top hat will do and an MK bus bar for the neg side.