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Replacing fuses with MCB's



 
 
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  #1  
Old January 17th 06, 09:08 PM posted to uk.d-i-y
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Default Replacing fuses with MCB's

My 25 year old MEM consumer fuse box is still in A1 condition and I've
only had two fuses blow during that peiod. However I do feel I ought
to update and fit some MCB's.

My MEM fuses screw onto the live buss bar and the other side of the
fuse takes the wire for the ring main or whatever.

Can I replace these fuses directly with a screw on MCB like say this
from ScrewFix...
MK 16A SP Type B MCB 6kA

....or do I have to replace the consumer box to one that just has a clip
on supporting rail with the supply main wire going in one side of the
MCB and the ring main wire into the output side.

T I A Chris.

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  #3  
Old January 17th 06, 09:54 PM posted to uk.d-i-y
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Default Replacing fuses with MCB's

First question is: what problem are you trying to fix? Does your
existing CU have rewireable fuses or cartridge fuses?

I do NOT have a problem. I just wish to upgrade from fuses to MCBs.
My fuses are rewireable types.

The pictures I've seen of MCBs seem to just clip onto a support bar and
have a screw terminal at each side for wires. If they screw to a buss
bar I'd only expect to see one screw terminal for the output to the
ring or spur or whatever.

Chris.

Chris.

  #4  
Old January 17th 06, 10:17 PM posted to uk.d-i-y
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Default Replacing fuses with MCB's

You'll be lucky to find a compatible MCB for such an old unit. HAs the
unit got a 'smoked grey perspex cover' on it? if so, are the 'prongs'
on the fuse carriers oriented side to side or are they top to bottom?


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  #7  
Old January 17th 06, 11:11 PM posted to uk.d-i-y
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Default Replacing fuses with MCB's

wrote:

First question is: what problem are you trying to fix? Does your


existing CU have rewireable fuses or cartridge fuses?

I do NOT have a problem. I just wish to upgrade from fuses to MCBs.
My fuses are rewireable types.


MCBs do offer greater ease of use, however if you are not having to
rewire fuses on a regular basis then there is only a limited amount to
gained from the change. MCBs represent slightly better protection in
most cases, but not that much in absolute terms assuming the wiring is
in a reasonable state (rewireable fuses are still permitted in the
current wiring regs). If you are looking to improve safety then you may
get more "bang for your buck" making sure you have RCD protection where
it will give best advantage.

The pictures I've seen of MCBs seem to just clip onto a support bar and
have a screw terminal at each side for wires. If they screw to a buss
bar I'd only expect to see one screw terminal for the output to the
ring or spur or whatever.


There are not usually any side connections on MCBs

Take as an example:

http://www.tlc-direct.co.uk/Products/CM7106B.html

The bottom screw and terminal is used to secure the MCB to the busbar.

A busbar is usually comb like:

http://www.tlc-direct.co.uk/Products/MK5590.html

The prongs of the bar poke into the bottom terminal of the MCB and the
screw is done up. The end prog of the bar pokes into the bottom terminal
of an incomer switch or RCD which is fed from the meter tails which fix
into the top connection.

The rear of it clips to the DIN rail, and the top screw is used to clamp
the wires to the circuit.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/
  #8  
Old January 18th 06, 09:16 AM posted to uk.d-i-y
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Default Replacing fuses with MCB's

There are not usually any side connections on MCBs
Take as an example:
http://www.tlc-direct.co.uk/Products/CM7106B.html
The bottom screw and terminal is used to secure the MCB to the busbar.
A busbar is usually comb like:
http://www.tlc-direct.co.uk/Products/MK5590.html


Ah! The buss bar has prongs, I see now. Thanks fot the picture.

The wiring is only 25 years old and done with all the same wire type as
today. As I said I've only had two/three fuse blow in 25 years, one
self inflicted, one due to a mouse and one due to a light bulb blowing.

The CU does have the two smoked perspex drop down windows that give
access to the 12 fuses. About five years ago I did tidy it all up when
I inserted a new ring main in a new bedroom and replaced the above
mouse bitten cable.

The only reason for replacing the fuses with MCBs was to make it a bit
more up to date so that if I did sell up the next person wouldn't have
to call out a Lektrishun to replace a fuse.

Chris.

  #10  
Old January 18th 06, 12:17 PM posted to uk.d-i-y
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Default Replacing fuses with MCB's

wrote:

The only reason for replacing the fuses with MCBs was to make it a bit
more up to date so that if I did sell up the next person wouldn't have
to call out a Lektrishun to replace a fuse.


I would have thought if you were going to replace it, it would only be
worth doing if you were going to upgrade the whole thing so that you
could have some form of split load affair to give you RCD protection on
sockets etc, and to make sure all the equipotential bonding is up to
scratch (since you can almost guarantee that will be a comment on a
survey if not to current standards). You make life much simpler with
obtaining suitable MCBs etc if you choose a current model of CU rather
than sticking with one that uses bespoke parts that may be in short supply.

It would give you the chance to split existing circuits or add new ones
where appropriate (like a dedicated ring circuit for the kitchen perhaps)

You could also design in a few extra nice touches like battery
maintained emergency light close to the CU that is powered from the same
MCB as the lighting circuit that usually illuminates the CU - that way
if the circuit trips you can still see what you are doing to reset it.

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd -
http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/
 




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