On Mon, 29 Jan 2018 14:48:18 +0000, dennis@home wrote:

On 29/01/2018 14:38, jim wrote:
"dennis@home" Wrote in message:
On 29/01/2018 13:05, jim wrote:

Does retrofitting mcbs into an older wylex "fuse wire" consumer
unit need notification?

The plug in ones don't have the same breaking capacity as te fuse wire
so you may need to check they are OK.

The plug in MCBs (if that's what you are using) can't cope with as much
fault current as the more common MCBs or fuse wire.



Erm eh?

But why bother? I haven't had a fuse wire go in 30 years so fitting
MCBs would be a waste of time IMO.

Elderly (tight) rellies can't fit occasional fusewires into old
carriers.


If they are having fuses blow then maybe the circuits need fixing rather
than making them easier to reset without fixing them. I can't see why
they would blow for decades.

+1

In 35 years, I've only ever had to replace/rewire a blown fuse just the
once (I keep spare fuses handy to the CU[1]). Even so, this was due to my
being less than scrupulously careful when packing the wires into a metal
back box after rewiring a single outlet socket. I'd managed to trap one
(possibly both) live wire(s) which caused a framing fault on the ground
floor ring main circuit a day or two later. A quick check of the sockets
I'd been working on revealed the fault soon enough for me to fix my
mistake and restore the ring main back into service ever since then.

[1] It's well worth "The Expense" of keeping a set of spare rewireable
fuses handy to the CU to remove any sense of urgency which might lead to
mistakes in rewiring a fuse with the wrong gauge of fusewire (especially
true in the case of a blown lighting circuit repair using torchlight to
see what you're doing).

This provides almost as much "convenience" as resetting a circuit
breaker when dealing with a 'nuisance fault' but not so much convenience
as to make it all too easy to avoid "Doing the right thing by tracking
down the cause" and dealing with the actual fault in a timely manner.

With circuit breakers, there's always the temptation to keep resetting
the breaker to deal with the symptom until either the fault gets to the
point it can no longer be ignored or the circuit breaker itself fails
with the contacts welded shut.

A spare fuse gives you a one shot chance at clearing a 'nuisance fault'
and the chance to rewire the blown fuse at your leisure to provide
another shot at clearing the next nuisance fault that might arise hours
to days later. In the case of a persistent 'nuisance fault', you'll get
fed up with rewiring fuses far sooner than resetting a circuit breaker
which will result in the cause being investigated and repaired sooner
rather than later which is no bad thing.

Quite frankly imo, the use of MCBs in a domestic setting has always
looked like "A solution in search of a problem". ELCBs/RCBOs less so
since they bring earth leakage protection against the risk of
electrocution to the table. I see no benefit in replacing plug in fuses
with plug in MCBs in a domestic CU since they offer no greater protection
than a fuse, only the convenience of making a potentially hazardous
circuit live once more.

--
Johnny B Good