"BigWallop" wrote in message
...
The consumer unit should have 16mm double insulated tails from the meter,
but yours has only got double insulated on the black phase and the red
phase
is open to being more easily damaged and exposing the bare conductor.
They
are all 16mm though, so are normal for this type of installation.
Erm - could you explain that a little simpler (I did do an Elec Eng degree
though - honest!). Is it the tails that's a problem, or the design of the
CU itself?
The fuse configuration I'd say is back to front, with the heaviest load
appliance (shower) being taken from the furthest point from the supply
side
of the bus bar. This can cause lights to dim a bit more than they should
when the shower is switched on and off, and can also cause heating along
the
full bus bar because all the heaviest use loads are furthest from the
supply.
The lights do dim/brighten when the shower is turned on/off - so that might
explain why its more noticable than I might have expected.
Working from the switch, the first white cartridge is lighting and looks
to
have a 1mm cable which is normal. The blue cartridge is for a heater of
some sort (water) and looks to have a 2.5mm cable, this to is normal. The
second white fuse is also lighting and looks to have 1mm, which again is
normal and a good idea to separate lighting over two supplies in case one
pops, you have the other as a sort of backup for safety.
The blue 16A MCB most certainly does the upstairs lighting - someone (when I
enquired about this before) wondered if someone had accidentally swapped the
lighting and the immersion heater over (which is fed from a single socket in
the airing cupboard). This is possible, and I will check this sometime by
plugging a light into that socket and turning off the 6A MCB and see if it
goes off (which is pretty much how I've worked out which circuit goes
where). This socket though used to be attached to the wall at some point in
history, now its lying on the bottom of the airing cupboard and rattles - so
I've avoided using it because a.) I've no idea what's inside (ie. conductive
or not conductive), b.) there's holes in the back of the socket which are
accessible and c.) We get plenty of water from our central heating! It's on
my job list of things to check out though!
Further (larger, less compressed) pictures of the CU can be found at:
http://www.swampie.ukfsn.org/ConsumerUnit1.jpg
http://www.swampie.ukfsn.org/ConsumerUnit2.jpg
http://www.swampie.ukfsn.org/ConsumerUnit3.jpg
http://www.swampie.ukfsn.org/meter.jpg
The first red holder from the switch looks to be a ring circuit due the
two
red 2.5mm cables going to it, which is normal. The second red fuse seems
to
be a ring circuit as well, but also has a spur off to somewhere (?)
because
it has three red 2.5mm cables connected.
This could either be a single socket, or maybe the feed to the garage (via a
FCU at the end of the kitchen).
The last red connection has a 6mm
cable attached, by the look of it. For a load of around 7 or 8 killowatts
over a short length of cable, then this guage would probably take it
without
complaining to much. But I would not chance going any higher in the Watts
rating on this, no matter how short a run this cable is. I'd say it is
safer to go with 10mm on a load over 8 kW and reduce the effect of any
possible heating totally and completely, and also gives a less resistive
path back to earth with the thicker conductor that is already supplied in
it. But then I always err' on the side of caution with these things.
That's fine - the shower is working fine at the moment and we've got no
plans to change it. It was more of a "I wonder..." type thought.
I'd also say the earthing conductor, which currently looks like a 16mm
cable, is also quite normal for this type of installation, but I'd like to
be able to see where it is connected at the other end.
http://www.swampie.ukfsn.org/earthing.jpg
All in all, it is a normal installation for this size of dwelling, but as
I
said in the first paragraph, I think it is back to front. Although others
will probably disagree with this idea.
Its an old-ish install in a 1930's semi. We've got no plans to replace the
CU (if we did replace it, I'd probably do it myself, but planning on doing
nothing other than just a new CU and swap circuits over (no plans on
rewiring etc - plenty of other jobs needed) - which probably isn't really
worth it - except maybe like to put RCD's onto the rings + shower (I know
about freezers being tripped!) ) I take it that it would just be a job of
putting a 2nd set of tails from the meter output (there's a few spare holes
to add some more tails) and wire it to a new CU. Then move a circuit across
at a time. Of course, remove the incoming main fuse first though!
So - can I expect that the immersion circuit and the upstairs lighting
circuits are the wrong way around? Should it be 2.5mm cable for the
immersion heater, and 1mm (or more) for the lighting? If the blue MCB has
1mm wiring and the white one has 2.5mm then its probably wired wrong, if
they've all got 1mm then I'm stuck. I guess its hard to see the difference
in the pictures (hence putting up uncompressed pictures).
And I'll drill through the joists to add my ring extension, using 2.5mm.
Thanks for your (and everyone else's) help.
D