I know this is a slightly odd question, I will try and explain.

I am [re-]wiring a small boat that we have recently bought in Belgium,
I've done all the low voltage 12 volt (ELV strictly I guess) stuff and
am now moving on the to mains supply which (mostly) will only be used
when we're moored at places with shore supply available.

I'm fairly au-fait with all the issues with isolation from shore,
proper protection with RCD, etc. etc. I've already sorted out some
rather major fundamental nasties on that front (wrong way round
connectors leaving live pins when unplugged, no RCD protection, etc.)
but I am left with one nuisance problem that I haven't really solved
yet.

The boat has mostly french/belgian type sockets at the moment, most of
our mains electrical stuff however (of course) has standard UK plugs.
There are very few (if any) of the existing sockets in the boat which
are worth preserving and, after quite a lot of thinking, mucking
about, asking questions here, etc. I have decided that the easiest
solution will be to go to all UK sockets with adapters (or, possibly,
extension leads) for the equipment with french/belgian plugs, with a
longer term aim of changing plugs.

Finally to the question, space is limited on the boat and there are
very few places where flush mounted sockets are possible so the
neatest solution is to use two and four way 'trailing sockets' (as in,
the sockets of a multi-way extension lead). However these are
supposed to be protected by a 13 amp fuse in the plug, I really want
to wire them permanently and, if I do this, they will be protected by
16 amp MCBs. It feels to me as if this should be OK as 16 amp MCBs
will, in reality, probably trip at or close to the same current levels
as a 13 amp fuse.

Does this seem a reasonable/safe approach? It doesn't have to conform
to any specific wiring regulations (which it almost certainly won't),
no one is ever going to inspect the wiring of the boat at that sort of
level of detail. On the other hand I do want it to be safe for the
usual mix of family and friends as well as for me.

What does the team think?

--
Chris Green

wrote in message news
Does this seem a reasonable/safe approach? It doesn't have to conform
to any specific wiring regulations (which it almost certainly won't),
no one is ever going to inspect the wiring of the boat at that sort of
level of detail. On the other hand I do want it to be safe for the
usual mix of family and friends as well as for me.

What does the team think?

A lot of fourway strips have integral fuses.
If you use one of these then the MCB will only be protecting the flex.
The integral fuse is providing the protection that the manufacturer thinks
it needs.
Of course, as you say, the 16A MCB will probably offer better protection
than the fuse anyway.

On Nov 11, 2:42*pm, John Rumm wrote:

a 16A MCB will be somewhat more tolerant to sustained overload than a
13A fuse. If you compa

http://wiki.diyfaq.org.uk/index.php?...FusingTime.png

with

http://wiki.diyfaq.org.uk/index.php?...e-MCBTypeB.png

That's an eye opener!

The number printed on the fuse (or MCB) is clearly proportionally
related to its characteristics, but what part of those response curves
does it actually relate to?! 1/5th of the instantaneous current?
2/3rds of the long term current? Why not an actual number that
actually sits on the response curve (somewhere!)?

(apologies if the PDF you linked to answered this - it won't open
here).

Cheers,
David.

In article ,
wrote:
[snip background]


Finally to the question, space is limited on the boat and
there are very few places where flush mounted sockets are
possible so the neatest solution is to use two and four
way 'trailing sockets' (as in, the sockets of a multi-way
extension lead). However these are supposed to be
protected by a 13 amp fuse in the plug, I really want to
wire them permanently and, if I do this, they will be
protected by 16 amp MCBs. It feels to me as if this
should be OK as 16 amp MCBs will, in reality, probably
trip at or close to the same current levels as a 13 amp
fuse.
If you buy the trailing sockets in France/Belgum they will
not have a fuse anyway, as the 13amp fused plug is only a UK
thing (in this context) so should not be a problem.

Does this seem a reasonable/safe approach? It doesn't
have to conform to any specific wiring regulations (which
it almost certainly won't), no one is ever going to
inspect the wiring of the boat at that sort of level of
detail. On the other hand I do want it to be safe for
the usual mix of family and friends as well as for me.
The more time you spend there, the more likley you are to
buy foreign stuff, then sourcing a different wall wart for
your latest gizmo becomes a problem. I'd suggest a mix of
trailing leads. (We have a block of UK sockets for the
g/children to charge their mobiles, game-boys etc. rather
than a load of adaptors which get lost in drawers or packed
in suitcases when they leave.

What does the team think?
If you moor outside the 3 mile limit perhaps you could
create your own regs ;-)

John

--
John Mulrooney
NOTE Email address IS correct but might not be checked for a while.

Tidy desk tiny mind!

In article , writes

Finally to the question, space is limited on the boat and there are
very few places where flush mounted sockets are possible so the
neatest solution is to use two and four way 'trailing sockets' (as in,
the sockets of a multi-way extension lead). However these are
supposed to be protected by a 13 amp fuse in the plug, I really want
to wire them permanently and, if I do this, they will be protected by
16 amp MCBs. It feels to me as if this should be OK as 16 amp MCBs
will, in reality, probably trip at or close to the same current levels
as a 13 amp fuse.

How about these? They have an integral 13A fuse, and while intended to
fit an existing sunken double backbox, could probably be adapted to fit
your boat. I have one at home waiting to be fitted and the gubbins
sticking out of the back needs only a shallow recess.

http://ebulbshop.com/acatalog/Conver...to_4_Gang.html

I got mine for 3.50 ish from Wilkinsons.

--
Mike Tomlinson

In article
, John
Rumm wrote:
Short answer, I would use a 10A MCB rather than a 16.
That will let you draw 15A pretty much indefinitely.
French regs allow up to 5 sockets on a radial 10A circuit
and up to 8 per 16A circuit, but never any advice about max
no of trailing sockets or adapters

--
John Mulrooney
NOTE Email address IS correct but might not be checked for a while.

Knowledge is knowing a tomato is a fruit; Wisdom is not putting it in a fruit salad

John Rumm wrote:
On 11/11/2010 13:56, wrote:

I know this is a slightly odd question, I will try and explain.

[snip]

Finally to the question, space is limited on the boat and there are
very few places where flush mounted sockets are possible so the
neatest solution is to use two and four way 'trailing sockets' (as in,
the sockets of a multi-way extension lead). However these are
supposed to be protected by a 13 amp fuse in the plug, I really want
to wire them permanently and, if I do this, they will be protected by
16 amp MCBs. It feels to me as if this should be OK as 16 amp MCBs
will, in reality, probably trip at or close to the same current levels
as a 13 amp fuse.

Does this seem a reasonable/safe approach? It doesn't have to conform
to any specific wiring regulations (which it almost certainly won't),
no one is ever going to inspect the wiring of the boat at that sort of
level of detail. On the other hand I do want it to be safe for the
usual mix of family and friends as well as for me.

What does the team think?

Short answer, I would use a 10A MCB rather than a 16. That will let you
draw 15A pretty much indefinitely.

There is evidence that some of the lower quality (i.e. probably cheaper)
4 way leads are not adequately protected by their 13A fuse - since this
will usually permit a sustained load of 20A and not all of them are up
to that. Read the report starting page 18:

http://www.esc.org.uk/pdfs/business-...n-Issue-18.pdf

All of the failures noted there seem to have been in the plug which I
am going to remove, thus it would seem that my usage will actually be
safer, I just need to keep an eye on the sockets.


a 16A MCB will be somewhat more tolerant to sustained overload than a
13A fuse. If you compa

http://wiki.diyfaq.org.uk/index.php?...FusingTime.png

with

http://wiki.diyfaq.org.uk/index.php?...e-MCBTypeB.png

It's difficult to compare but if my interpretation of the fuse curves
is right (I'm assuming a 13 amp fuse lies in the *band* between the
two RH curves) then a 13 amp fuse can be distinctly worse than a 16
amp MCB can't it? E.g. at 30 amps a 13 amp fuse could take up to 400
seconds to blow whereas a 16 amp MCB will trip after about 200
seconds. It's not a big difference though.

I do have some 10 amp MCBs so could go with them I guess, the supply
as a whole can only provide 16 amps. Maybe I could put in one set of
full sized sockets where, if/when needed anything that draws close to
the limit can be plugged in.

Thanks for the links and advice.

--
Chris Green

JTM wrote:
In article
, John
Rumm wrote:
Short answer, I would use a 10A MCB rather than a 16.
That will let you draw 15A pretty much indefinitely.
French regs allow up to 5 sockets on a radial 10A circuit
and up to 8 per 16A circuit, but never any advice about max
no of trailing sockets or adapters

That's a useful guideline to throw into the mix, thank you.

--
Chris Green

JTM wrote:
In article ,
wrote:
[snip background]


Finally to the question, space is limited on the boat and
there are very few places where flush mounted sockets are
possible so the neatest solution is to use two and four
way 'trailing sockets' (as in, the sockets of a multi-way
extension lead). However these are supposed to be
protected by a 13 amp fuse in the plug, I really want to
wire them permanently and, if I do this, they will be
protected by 16 amp MCBs. It feels to me as if this
should be OK as 16 amp MCBs will, in reality, probably
trip at or close to the same current levels as a 13 amp
fuse.
If you buy the trailing sockets in France/Belgum they will
not have a fuse anyway, as the 13amp fused plug is only a UK
thing (in this context) so should not be a problem.

But they're going to be UK sockets, so rather difficult to buy in
France or Belgium.


Does this seem a reasonable/safe approach? It doesn't
have to conform to any specific wiring regulations (which
it almost certainly won't), no one is ever going to
inspect the wiring of the boat at that sort of level of
detail. On the other hand I do want it to be safe for
the usual mix of family and friends as well as for me.
The more time you spend there, the more likley you are to
buy foreign stuff, then sourcing a different wall wart for
your latest gizmo becomes a problem. I'd suggest a mix of
trailing leads. (We have a block of UK sockets for the
g/children to charge their mobiles, game-boys etc. rather
than a load of adaptors which get lost in drawers or packed
in suitcases when they leave.

I was originally going to have a mix of trailing blocks but I then
decided that there would always be the wrong one in the wrong place.

I think keeping things flexible (no pun intended) is probably a good
idea though.

--
Chris Green

Mike Tomlinson wrote:
In article , writes

Finally to the question, space is limited on the boat and there are
very few places where flush mounted sockets are possible so the
neatest solution is to use two and four way 'trailing sockets' (as in,
the sockets of a multi-way extension lead). However these are
supposed to be protected by a 13 amp fuse in the plug, I really want
to wire them permanently and, if I do this, they will be protected by
16 amp MCBs. It feels to me as if this should be OK as 16 amp MCBs
will, in reality, probably trip at or close to the same current levels
as a 13 amp fuse.

How about these? They have an integral 13A fuse, and while intended to
fit an existing sunken double backbox, could probably be adapted to fit
your boat. I have one at home waiting to be fitted and the gubbins
sticking out of the back needs only a shallow recess.

http://ebulbshop.com/acatalog/Conver...to_4_Gang.html

I got mine for 3.50 ish from Wilkinsons.

Boats tend not to have anywhere one can mount 'flush' boxes because
the other side of that panel you can see is either water or another
cabin (or inside a storage space).

--
Chris Green

writes:

Boats tend not to have anywhere one can mount 'flush' boxes because
the other side of that panel you can see is either water or another
cabin (or inside a storage space).

They (Homebase, B&Q, CPC) sell triple 13 A. sockets with one integral
13a. fuse which are capable of either surface mounting using the
supplied plastic back box or recessed mounting into an MK triple metal
pattress (though the latter is difficult to find).
Primarily intended to convert an existing single socket to a triple
socket, and the built-in fuse protects against overload.

Though of course that doesn't help much if you also want European
sockets.

(This is irrelevant to your query, but it's interesting to compare
fusing curves for old rewireable consumer unit fuses with those for
the cartridge fuses which for a time replaced the rewireables.
The rewireables seemed to blow more quickly so better protection.
But of course more risk that someone would then replace the fuse
wire with a chunk of heavy copper wire from a cable, which would be
a very dangerous thing to do).

--
Windmill, Use t m i l l
@ O n e t e l
. c o m