I'm looking for a consumer unit to use for the 12 volt DC switchboard
in our boat. While I'm pretty sure *any* MCBs will actually work at
12 volts I'm aiming to use a make which actually specifies that 12
volts is OK.
The available makes I have found so far which say 12 volts is OK are:-
The Electrium family (Wylex, Crabtree, Volex and a lot of wholesaler
own-brands) only say down to 24 volts. MK doesn't specify DC at all.
So my front runners at the moment are Contactum (very good prices from
TLC at the moment) and Square-D (from Toolstation probably). At the
moment I'm leaning towards a Contactum metal consumer unit.
Does anyone have any recommendations (or otherwise) for any of these
On 20/07/2010 12:32, firstname.lastname@example.org wrote:
I have used quite a bit of the contactum stuff - although more often the
plastic rather than metal clad enclosures. On the plus side, its cheap,
has plenty of space and is easy to work on. The plastic is quite soft -
which is not a bad thing - it cuts easily enough without shattering. The
unused way blanking plugs are just caps that plug into the gap rather
than the more elaborate dummy MCB type approach used by hager and MK
etc. The range of devices they produce is not as wide as hager or MK
(although the latter will usually fit the contactum boxes!)
Of the others Hager are pretty good all round IME, MK also but pricey.
MEM tend to be more focused on the commercial sector and their stuff can
tend to be a little less "standard", but the quality is usually very good.
Proteus seem to be gaining popularity and acting as OEMs for a number of
other brands, but I have had some rather unpleasant experiences with
some of their kit (notably MCBs that only electrically turn on one time
in three when you mechanically turn them "on" - that can make fault
finding harder than it ought to be!)
OK, thanks, gap plugs are relatively unimportant at 12 volts. Also I
agree about the smaller range of accessories but I don't think I need
any and, as you say, other makes will fit.
MK are ruled out by not saying they work at 12 volts in their
specification, they probably do work but with MCBs that are specified
to work at 12 volts I have some comeback if things don't work as they
OK, so probably won't choose Proteus then, I can't find a reasonably
priced supplier anyway!
On 20/07/2010 15:00, email@example.com wrote:
I have used three contactum CUs on my place (all plastic - we are TT
here), and generally I quite like them. I needed to fit MK type S RCDs,
and a Hager HRC fuse carrier. The only slight annoyance is they subtly
changed their design recently and the old an new MCB are not quite a
perfect interchange (you can force wm because the box is soft enough!)
However if buying now that is unlikely to be a problem for you.
This is 12V, so you need reliable disconnection.
Schneider used to make Merlin-Gerin, Square-D & MK brands.
MEM are well regarded.
So I would go with whichever is cheapest.
Might be worth calling their tech helplines to see if any "application
notes" re 12V operation.
On Tue, 20 Jul 2010 12:32:59 +0100, tinnews wrote:
They specify down to 24 volts because of the contact material. It is
designed for mains switching and there may be insufficient voltage below
24v to break through the thin film of oxide that can form on the contacts
while open for any extended period of time. Note that if the contacts are
closed the oxide film isn't a problem and you can go down to lower
voltages. That would normally be the case for a consumer unit.
Also, as I mentioned in a previous post, sometimes DC ratings on
switchgear are only given *below* 30vDC or 48vDC because the contacts
don't open far enough to break a DC arc from an inductive load at much
above that! Makes it fun choosing DC switchgear...
GE Power Controls do a "proper" range of DC mcbs. EP100UC These are rated
down to 12v.
ABB S200M are also rated down to 12vAC/DC.
There are some mcbs here:
that, although they don't give minimum voltage ratings, do show all sorts
of information. This includes temperature compensation etc. Not often you
find all the curves. I've not used their mcbs on jobs of any size, but
they seem to be ok and were reasonably priced IIRC.
Mick (Working in a M$-free zone!)
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