wrote:
On Aug 1, 1:13 am, John Rumm wrote:
wrote:
Rewirable fuses are still fully compliant for new installation. You'd
derive very little safety benefit from adding MCBs. The reason the
fuses didnt pop is that any trip device takes a cvertain amount of i
times t to blow, and the fault, while it may have looked impressive,
didnt draw enough i x t, and the fault blew itself open circuit first.
You may have been scared by this, but safetywise its pretty much a non-
issue.
While this is true, there are two caveats worth mentioning: If the
cables are the older style PVC with only a 1mm^2 CPC (modern cable has
1.5mm^2) then it is worth moving away from rewireable fuses since the
protection will be marginal or insufficient in many cases.

1mm2 T&E CPC will not have any difficulty at all blowing rewirable
fuses. Its a long way from marginal. What can be marginal is its
compliance with disconnect times for new wiring regulations - but
thats nowhere near enough of an issue to prompt a CU replacment for
99% of the population.

If it can't achieve the required disconnect time, then it is at best
marginal. (and that's just the old 0.4 sec requirement).

As we have both said, the question of whether a BS 3036 semi-enclosed
fuse CU should be replaced is a broader question that needs to take
account of a number of factors. Compatibility with the installed wiring
is one factor.

If the power
(i.e. socket) circuits currently have no RCD protection then again it is
worth introducing this, which realistically will also mean a CU swap.

Again, the benefit exists but is so small that only a miniscule
percentage of the population would consider it worthwhile to fit the
new CU. Almost no-one rewires their house every time a minor safety
advance comes along.

No, I disagree strongly with this. There is no way you can call a RCD a
"minor safety advance". RCD protection makes a significant impact on the
survivability of electric shocks, and unlike nonsense like part P, the
the use of them has a big impact preventing death and serious injury as
a result of (ab)use of hand held appliances (which as we know is a
significant number, unlike those attributable to fixed wiring faults).



--
Cheers,

John.

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