On 27/07/2018 15:59, Scott wrote:
On Tue, 17 Jul 2018 14:31:32 +0100, "Dave Plowman (News)"
wrote:

Just has a letter from UK Power Networks stating their records show I have
one of these which is outdated and needs to be replaced urgently.

Be interested to know why this has suddenly become urgent. ;-)

However, mine was replaced by a single line fuse with neutral link some 40
odd years ago - before I bought this house.

But the point of this post is the diagram on the letter - to allow you to
identify your unit - shows an earth terminal as being part of their
obligatory supply. Last time I checked, this wasn't the case. Have the
regs changed? Can I demand they fit one FOC?

Just to go back to basics, does anyone know why these were installed
in the first place if they were dangerous, apparently ineffective and
involved additional cost? Was it a throwback to DC supply?

It could have been a DC supply, but equally could have been some types
of AC supply as well. There was a time (we are talking before national
grid and standardisation of supply arrangements here) where the
supplier's earth was joined to a centre tap on the transformer. So you
may have had a situation where earth was at a potential midway between L
and N. You could get a shock from L to E, but also N to E since they
were not bonded together as in current supply arrangements.

(there were even dual fused consumer units / fuse boards at one point)

I wonder how they deal with this in the US (where this style of centre
tapped supply is common), when running 220V appliances that are fed from
both of the 110V lives? I would expect in this day and age they would
insist on the circuit breaker being a double pole device - but wonder
what they did with fuses?


--
Cheers,

John.

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