The box says total load 60 amps.

OK, there's two 30 amp circuits, two 5 amp circuits, a 15 amp
shower and a spare. I want to put a 32 amp cooker on the spare.
clearly the load isn't just all those added together. Anybody
know somewhere I can find typical figures for the load from the
house or suggest an answer?

I have:-
fridge, freezer
TV, PC, usual number of lights.
shower, 2 small heaters upstairs, elec blanket.

(no immersion).

the heaters would be 1KW or less , so that's 1000 / 240 = (about)
4 amps for each heater if my schoolboy physics is still
functioning.

shower on 15 amp fuse cant be more than 12
two heaters + blanket 12?
cooker 28?

that could be 52 without all the little things if everything was
running at once?
--
Mike Reid
Walk-eat-photos UK "http://www.fellwalk.co.uk" -- you can email us@ this site
Walk-eat-photos Spain "http://www.fell-walker.co.uk" -- dontuse@ all, it's a spamtrap

The Reid wrote:

The box says total load 60 amps.

OK, there's two 30 amp circuits, two 5 amp circuits, a 15 amp
shower and a spare. I want to put a 32 amp cooker on the spare.
clearly the load isn't just all those added together. Anybody
know somewhere I can find typical figures for the load from the
house or suggest an answer?

You'll find _an_ answer in Table 1B of the IEE On-Site Guide (OSG).
(But apply that to a lot of house installations an you'll come up with
an ADMD (after diversity max. demand) of 150 - 200 A! So some common
sense has to be applied too.

Anyway, using Table 1B, in your case:

- two 30 A circuits - socket rings, presumably; allowance is 100% of
first cct. + 40% of others - so 42 A (this really is over-generous, IMHO);

- two 5A circuits - lights; allow 66% of actual max. load, let's say 6 A
(assuming 2 kW of lighting);

- 15 A shower? - perhaps you meant immersion heater - anyway assume 3 kW
or 13A (no diversity allowed for water heating);

- total so far, 61 A;

- add cooker: assume typical free-standing cooker - about 12 kW flat-out
(52 A, diversity rule is first 10A plus 30% of remainder, giving 23 A -
new total 84 A.

So applying the OSG strictly you'd need to upgrade to a 100 A supply.
In practice you won't have any problem and (IME) the electricity
companies don't worry over-much about this sort of thing. Anyway 84 A
is only a small overload and will do no harm for short periods (it
certainly won't blow your main fuse).

(no immersion).

Oh, no immersion. So what's the 15 A fuse feeding - an old 3 kW instant
electric shower? (and people think the 9 kW ones are poor) - or a shower
pump (with gas or oil water heating)? If it's a shower pump you can
reduce the 13 A I assumed above to one or two amps.

If that is an old 3 kW shower and you ever upgrade it to a modern one,
that would be the time to get your supply uprated.

HTH
--
Andy

OK, there's two 30 amp circuits, two 5 amp circuits, a 15 amp
shower and a spare. I want to put a 32 amp cooker on the spare.

It depends what you mean by "shower". An electric shower is usually 32-45A.
Perhaps you mean a shower pump on its own circuit?

Personally, 60A would be fine, provided you have only one of an electric
cooker and electric shower. If you have both, then I'd be tempted to get
them to stick a 100A cutout on it. If you have mainly electric heating, then
you should be aiming for 3 phase.

Christian.

Following up to Andy Wade

So what's the 15 A fuse feeding - an old 3 kW instant
electric shower?

yes! (something to note if I upgrade shower, never realised they
are 9 now!!! )
And thanks for the rest of the info.

Two more questions (I'm still vacillating between DIY and getting
a new fusebox fitted)
1. What is the view on a ring main junction box for a spur
mounted on the wall near the fusebox rather than under the floor
(i need to free up the fuse the freezer is using) I really don't
fancy ripping up the floor to add a spur, alternatively I could
utilise the (repositioned) 13A supply to the old gas cooker with
a long cable, bit naff. but it would work.
2. Fuse holders. My Wylex fusebox has fuse-wire fuses (25 years
old) I tried to get a green coloured one for the cooker position
(perfectionist, me :-)) , the one I bought in a DIY shed turns
out to not fit Do people reckon I'll find one that fits in a
better shop?

Thanks again for all the help, I shall stay subscribed here (who
groaned at the back?) , bloody good group, hopefully I will be
able contribute something.
--
Mike Reid
Walk-eat-photos UK "http://www.fellwalk.co.uk" -- you can email us@ this site
Walk-eat-photos Spain "http://www.fell-walker.co.uk" -- dontuse@ all, it's a spamtrap

Following up to Christian McArdle

It depends what you mean by "shower". An electric shower is usually 32-45A.
Perhaps you mean a shower pump on its own circuit?

Old 3K unit it seems, I didnt realize how puny it was by modern
standards!

Personally, 60A would be fine, provided you have only one of an electric
cooker and electric shower.

The cooker will have two e. ovens (but there is only puny-shower)
and gas hobs (and a gas oven) wife has chosen a pretty fancy
cooker. (but 30A not 45A).
--
Mike Reid
Walk-eat-photos UK "http://www.fellwalk.co.uk" -- you can email us@ this site
Walk-eat-photos Spain "http://www.fell-walker.co.uk" -- dontuse@ all, it's a spamtrap

The cooker will have two e. ovens (but there is only puny-shower)
and gas hobs (and a gas oven) wife has chosen a pretty fancy
cooker. (but 30A not 45A).

I'd say 60A would work fine as it is then. However, enquire about a 100A
cutout, explaining that you have an electric cooker and shower. They might
pop round and upgrade you for free.

However, your consumer unit is old and relatively dangerous (wire fuses are
much worse than cartridge fuses or MCBs). I'd would strongly advise
replacement.

Christian.

Following up to The Reid

1. What is the view on a ring main junction box for a spur
mounted on the wall near the fusebox rather than under the floor
(i need to free up the fuse the freezer is using) I really don't
fancy ripping up the floor to add a spur, alternatively I could
utilise the (repositioned) 13A supply to the old gas cooker with
a long cable, bit naff. but it would work.

more I think about it, less I like the idea of something
unconventional, like that. Using the 13A cooker point is a more
conventional solution and with wiring, unconventional may be a
danger to those who come after. An extension cable goes with me
and poses no risk of confusion to others. Its going to be easier
than breaking into the ring anyway.
--
Mike Reid
Walk-eat-photos UK "http://www.fellwalk.co.uk" -- you can email us@ this site
Walk-eat-photos Spain "http://www.fell-walker.co.uk" -- dontuse@ all, it's a spamtrap

The Reid wrote:

yes! (something to note if I upgrade shower, never realised they
are 9 now!!! )

The highest powered ones are about 10.8 kW (needs 10 mm^2 cable).

1. What is the view on a ring main junction box for a spur
mounted on the wall near the fusebox rather than under the floor
(i need to free up the fuse the freezer is using) I really don't
fancy ripping up the floor to add a spur,

Either of those positions would be OK, but why not just wire the spur
into the fuse box? There's nothing to stop you taking a spur from the
origin of the circuit, in fact it's a better way.

2. Fuse holders. My Wylex fusebox has fuse-wire fuses (25 years
old) I tried to get a green coloured one for the cooker position
(perfectionist, me :-)) , the one I bought in a DIY shed turns
out to not fit Do people reckon I'll find one that fits in a
better shop?

Green is 45 A and won't fit the older Wylex boxes, as you've just
discovered. 30 A (red) one should be OK for your cooker circuit. If
you really need a 45 A circuit you'll have to get a separate 1-way Wylex
box and split the meter tails using service connector block (Henley block).

Individual domestic cooker circuits don't have to be rated for the full
appliance load, as the probability of having all the rings and things on
at once is tantamount to zero. You're allowed to use the same diversity
rule that I mentioned before - so if it's a 12 kW cooker the circuit
design current is 23 A and a 30 A fuse is quite OK. 6 mm^2 cable is
usual, but check the grouping and other derating factors to be sure.

--
Andy

Following up to Andy Wade

1. What is the view on a ring main junction box for a spur
mounted on the wall near the fusebox rather than under the floor
(i need to free up the fuse the freezer is using) I really don't
fancy ripping up the floor to add a spur,

Either of those positions would be OK, but why not just wire the spur
into the fuse box? There's nothing to stop you taking a spur from the
origin of the circuit, in fact it's a better way.

Right, why didnt I think of that? There's an example in the
existing wiring too (done by me with guidance 25 years ago). I
seem to be having a "senior day" with this job. Still, better to
ask stupid questions than screw up.

2. Fuse holders. My Wylex fusebox has fuse-wire fuses (25 years
old) I tried to get a green coloured one for the cooker position
(perfectionist, me :-)) , the one I bought in a DIY shed turns
out to not fit Do people reckon I'll find one that fits in a
better shop?

Green is 45 A and won't fit the older Wylex boxes, as you've just
discovered. 30 A (red) one should be OK for your cooker circuit. If
you really need a 45 A circuit you'll have to get a separate 1-way Wylex
box and split the meter tails using service connector block (Henley block).

Right, I'm the victim of procrastination here, I was going to do
a 45Amp set up, (to future proof) and bought 45A, then changed my
mind in face of the load issue. I'll get a 30 tomorrow.:-S

Individual domestic cooker circuits don't have to be rated for the full
appliance load, as the probability of having all the rings and things on
at once is tantamount to zero.

I was going to say the hobs gas anyway, but that's not the point
is it. Someone after me could do otherwise. Or even me in 5 years
time with my memory!

You're allowed to use the same diversity
rule that I mentioned before - so if it's a 12 kW cooker the circuit
design current is 23 A and a 30 A fuse is quite OK. 6 mm^2 cable is
usual, but check the grouping and other derating factors to be sure.

thanks again, (I have that cable). I reckon if I lurk in this
group I will be a lot better informed after a while!
--
Mike Reid
Walk-eat-photos UK "http://www.fellwalk.co.uk" -- you can email us@ this site
Walk-eat-photos Spain "http://www.fell-walker.co.uk" -- dontuse@ all, it's a spamtrap

Christian McArdle wrote:
The cooker will have two e. ovens (but there is only puny-shower)
and gas hobs (and a gas oven) wife has chosen a pretty fancy
cooker. (but 30A not 45A).

I'd say 60A would work fine as it is then. However, enquire about a 100A
cutout, explaining that you have an electric cooker and shower. They might
pop round and upgrade you for free.

However, your consumer unit is old and relatively dangerous (wire fuses are
much worse than cartridge fuses or MCBs). I'd would strongly advise
replacement.

Christian.

If you do replace it with a new split CU, it likely wont work at first,
there are liable to be issues.

NT

wrote:

Christian McArdle wrote:
However, your consumer unit is old and relatively dangerous (wire fuses are
much worse than cartridge fuses or MCBs). I'd would strongly advise
replacement.

If you do replace it with a new split CU, it likely wont work at first,
there are liable to be issues.

What sort of issues?

Anyway I don't agree with Christian - a 25 year old Wylex fusebox is
likely to be perfectly safe, assuming there's been no abuse like fitting
"uprated" fuse-wire.

It's old rubber-cable installations you have to watch, and really old
fuseboxes which have fuses in the neutral as well as the phase.

--
Andy

Anyway I don't agree with Christian - a 25 year old Wylex fusebox is
likely to be perfectly safe, assuming there's been no abuse like fitting
"uprated" fuse-wire.

Have you ever seen an unprotected wire fuse blow?

Quite frankly, I wouldn't be surprised if replacing the fuse wire with a
nail was actually safer!

Cartridge fuses are another matter. They are perfectly safe and the only
reason to change one of those for a modern unit is for convenience, or if
earth leakage protection is required and it is the simplest method to
achieve this.

Christian.

On Thu, 15 Dec 2005 15:15:16 GMT, wrote:

On 15 Dec,
"Christian McArdle" wrote:

Anyway I don't agree with Christian - a 25 year old Wylex fusebox is
likely to be perfectly safe, assuming there's been no abuse like fitting
"uprated" fuse-wire.

Have you ever seen an unprotected wire fuse blow?

Quite frankly, I wouldn't be surprised if replacing the fuse wire with a
nail was actually safer!

Cartridge fuses are another matter. They are perfectly safe and the only
reason to change one of those for a modern unit is for convenience, or if
earth leakage protection is required and it is the simplest method to
achieve this.

In some circumstances I'd prefer a fuse to an MCB. The rewirable ones are
perfectly ok in Wylex boards as long as the holder is intact and has the
correct size wire.

A 25 year old wylex can probably be upgraded to plugin MCBs quite easily.
They are available in the sheds and (cheaper) from TLC, and replace the
existing fuse and holder. The cover will require the knockouts removing as
well.

I think the MCBs are now cheaper than fuseholders (at B&Q anyway) !

--
Frank Erskine

"Christian McArdle" wrote in message
...
Anyway I don't agree with Christian - a 25 year old Wylex fusebox is
likely to be perfectly safe, assuming there's been no abuse like fitting
"uprated" fuse-wire.

Have you ever seen an unprotected wire fuse blow?

Many times and whilst a bit spectacular on the flash/bang front not anything
to be overly concerned about. Its not so many years since rewireable fuses
were the norm throughout the country. "REPEATED" rewireable fuses blowing
could however leave deposits of condensed copper on the (usually Asbestos)
target area and this has been known to carry more current than the fusewire
if not cleaned off or the target/enclosure replaced

Quite frankly, I wouldn't be surprised if replacing the fuse wire with a
nail was actually safer!

Stop eggaggerating, you will be sounding like dimm if you carry on.


Cartridge fuses are another matter. They are perfectly safe and the only
reason to change one of those for a modern unit is for convenience, or if
earth leakage protection is required and it is the simplest method to
achieve this.

The old Wylex boxes could be fitted with cartridge fuseholders or plug in
MCBs. However the fact remains Rewireable fuses are still acceptable.

John wrote:

"Christian McArdle" wrote in message
...

Have you ever seen an unprotected wire fuse blow?

Many times and whilst a bit spectacular on the flash/bang front not anything
to be overly concerned about. Its not so many years since rewireable fuses
were the norm throughout the country.

"Ditto" and "quite."

The old Wylex boxes could be fitted with cartridge fuseholders or plug in
MCBs. However the fact remains Rewireable fuses are still acceptable.

Indeed.

--
Andy

Many times and whilst a bit spectacular on the flash/bang front not
anything
to be overly concerned about.

I'm probably more cautious because I've seen a fire started by a rewireable
fuse, when it lit all the fluff that had accumulated on the consumer unit.
It was only luck that this fire didn't actually spread, although the scorch
marks were quite impressive.

Although still allowed by the regs, I would still replace any rewireable
fuse holder in any house in which I had some sort of interest in the safety
of. Even if not replacing the consumer unit, it's not expensive or difficult
to replace them with cartridge fuse holders or circuit breakers.

Christian.