My main fuse is rated at 60 Amp/500V.

Adding up all the circuits
5A Lighting
5A Lighting
16A Immersion
45A Shower
32A Ring
32A Ring
32A Cooker
___________
167A Total

Now I don't expect to have all circuits maxed out at the same time but the
full board is close to 3 times the main fuse rating.
If (which I probably won't) I ever had the immersion heater and shower on at
the same time I would be fairly near the loading of the fuse.
If I had both ovens and the electric hob going as well to cook Christmas
dinner then I might be drawing more than the rating on the fuse.

I do know that the lights dim slightly when the shower is switched on.

So how do you size the main fuse?
Is it linked to the capacity of the mains supply?
If so, when do you decide that youi have to uprate the mains supply?

Assuming 230V average supply I think I could draw up to 13.8Kw before
exceeding the fuse rating.

Could alsways use the energy monitor to test how much I draw with the main
appliances on :-)

Cheers

Dave R
--
No plan survives contact with the enemy.
[Not even bunny]

Helmuth von Moltke the Elder

(\__/)
(='.'=)
(")_(")

On Dec 22, 11:43*am, "David WE Roberts" wrote:
My main fuse is rated at 60 Amp/500V.

Adding up all the circuits
5A * * *Lighting
5A * * *Lighting
16A * *Immersion
45A * *Shower
32A * *Ring
32A * *Ring
32A * *Cooker
___________
167A * Total

Now I don't expect to have all circuits maxed out at the same time but the
full board is close to 3 times the main fuse rating.
If (which I probably won't) I ever had the immersion heater and shower on at
the same time I would be fairly near the loading of the fuse.
If I had both ovens and the electric hob going as well to cook Christmas
dinner then I might be drawing more than the rating on the fuse.

I do know that the lights dim slightly when the shower is switched on.

So how do you size the main fuse?
Is it linked to the capacity of the mains supply?
If so, when do you decide that youi have to uprate the mains supply?

Assuming 230V average supply I think I could draw up to 13.8Kw before
exceeding the fuse rating.

Could alsways use the energy monitor to test how much I draw with the main
appliances on :-)

Cheers

Dave R

The keyword is diversity


NT

"NT" wrote in message
...
On Dec 22, 11:43 am, "David WE Roberts" wrote:
My main fuse is rated at 60 Amp/500V.

Adding up all the circuits
5A Lighting
5A Lighting
16A Immersion
45A Shower
32A Ring
32A Ring
32A Cooker
___________
167A Total

Now I don't expect to have all circuits maxed out at the same time but the
full board is close to 3 times the main fuse rating.
If (which I probably won't) I ever had the immersion heater and shower on
at
the same time I would be fairly near the loading of the fuse.
If I had both ovens and the electric hob going as well to cook Christmas
dinner then I might be drawing more than the rating on the fuse.

I do know that the lights dim slightly when the shower is switched on.

So how do you size the main fuse?
Is it linked to the capacity of the mains supply?
If so, when do you decide that youi have to uprate the mains supply?

Assuming 230V average supply I think I could draw up to 13.8Kw before
exceeding the fuse rating.

Could alsways use the energy monitor to test how much I draw with the main
appliances on :-)

Cheers

Dave R

*The keyword is diversity



Really?
Cool - both my kids went.

--
No plan survives contact with the enemy.
[Not even bunny]

Helmuth von Moltke the Elder

(\__/)
(='.'=)
(")_(")

"NT" wrote in message
...
On Dec 22, 11:43 am, "David WE Roberts" wrote:
My main fuse is rated at 60 Amp/500V.

Adding up all the circuits
5A Lighting
5A Lighting
16A Immersion
45A Shower
32A Ring
32A Ring
32A Cooker
___________
167A Total

Now I don't expect to have all circuits maxed out at the same time but the
full board is close to 3 times the main fuse rating.
If (which I probably won't) I ever had the immersion heater and shower on
at
the same time I would be fairly near the loading of the fuse.
If I had both ovens and the electric hob going as well to cook Christmas
dinner then I might be drawing more than the rating on the fuse.

I do know that the lights dim slightly when the shower is switched on.

So how do you size the main fuse?
Is it linked to the capacity of the mains supply?
If so, when do you decide that youi have to uprate the mains supply?

Assuming 230V average supply I think I could draw up to 13.8Kw before
exceeding the fuse rating.

Could alsways use the energy monitor to test how much I draw with the main
appliances on :-)

Cheers

Dave R

*The keyword is diversity

Having Googled http://www.diy-forum.net/rating-main-fuse-t50249.html

100% of the biggest break + 40% of the rest
45 + (122*.4) = 93.8

Which suggests that I should have a 100A fuse.

Next question, what diameter main cable do I need to support this?
[a 60A fuse should not contribute to the lights dimming but insufficient
power through the main feed might]

Which also leads me to question why an electrician would fit a consumer unit
which had a diversity so far above the main fuse rating.

Obviously pre Part P, but is this normal practice?

Chers

Dave R

--
No plan survives contact with the enemy.
[Not even bunny]

Helmuth von Moltke the Elder

(\__/)
(='.'=)
(")_(")

On 22/12/2011 11:43, David WE Roberts wrote:
My main fuse is rated at 60 Amp/500V.

Adding up all the circuits
5A Lighting
5A Lighting
16A Immersion
45A Shower
32A Ring
32A Ring
32A Cooker
___________
167A Total

Now I don't expect to have all circuits maxed out at the same time but
the full board is close to 3 times the main fuse rating.

Indeed, and that is the fundamental point. Have a read of:

http://wiki.diyfaq.org.uk/index.php?..._for_Diversity

If (which I probably won't) I ever had the immersion heater and shower
on at the same time I would be fairly near the loading of the fuse.
If I had both ovens and the electric hob going as well to cook Christmas
dinner then I might be drawing more than the rating on the fuse.

Which in itself is not a problem - fuses blow on overload due to a
combination of both severity of overload and time. A 60A incomer fuse
will take 100A for a significant time without blowing. See the time Vs
current curves he

http://wiki.diyfaq.org.uk/index.php?....26_BS_1361.29

I do know that the lights dim slightly when the shower is switched on.

Yup, quite common. You would be able to measure a voltage drop quite
easily as a result of the load.

So how do you size the main fuse?

See above - however in reality, you normally get what you are given,
unless you specifically ask for more.

Is it linked to the capacity of the mains supply?

Sometimes, also quite often the size of the tails between the fuse,
meter and CU.

If so, when do you decide that youi have to uprate the mains supply?

When it keeps popping the fuse during normal everyday use.

Assuming 230V average supply I think I could draw up to 13.8Kw before
exceeding the fuse rating.

You could draw significantly more... see the comment about current and
time above.

Could alsways use the energy monitor to test how much I draw with the
main appliances on :-)




--
Cheers,

John.

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| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

There is no problem for 2 reasons...

#1 - Diversity.
It is unlikely that all circuits will be drawing max current at the
same time - and all the time.

#2 - Fuse does not blow at 60A.
A 60A fuse will happily carry 100A for some time, by design. A 100A
fuse requires over 1250A (0.3 megawatt) in order to blow within a
second or so. A 13A plug fuse requires 19.7A to blow within a second
or so.

Thus you can "overload" a 60A fuse to 90A for an hour or more, at 70A
the fusing time is probably near a day. Sorry can not read my BS1361
fuse chart properly (scan of a photo of a photocopy).

The only exception to this is two 45A showers - but even then both are
not likely to be operating at the same time AND a 90A load will not
blow a 60A fuse that quickly. The fuse above 60A is 80A, some
suppliers will upgrade for a fee. I recall they are downgrading 100A
to 80A for network reasons during routine work.

In article ,
"David WE Roberts" writes:
*The keyword is diversity

Having Googled http://www.diy-forum.net/rating-main-fuse-t50249.html

100% of the biggest break + 40% of the rest
45 + (122*.4) = 93.8

I regard this recommendation as out of date now.
It applied when everyone had 1 ring circuit, 1 lighting circuit, etc.
I generally install several of each now, so that any problems with one
are limited in scope, particularly when using RCBOs. That doesn't mean
that because my house has 4 ring circuits, it will be drawing any more
power than when it had just one.

Which suggests that I should have a 100A fuse.

Next question, what diameter main cable do I need to support this?

That counts as "suppliers works" and it's up to them.
It doesn't come under the wiring regs, and you will sometimes
find it's thinner than the wiring regs would have permitted.

[a 60A fuse should not contribute to the lights dimming but insufficient
power through the main feed might]

Which also leads me to question why an electrician would fit a consumer unit
which had a diversity so far above the main fuse rating.

60A is a bit low for anyone with an electric shower, but maybe he also
shares my views above, since you have 2 ring circuits. Nowadays, it
would make more sense to base the diversity load from all socket outlet
circuits on the total floor area supplied and if the house has central
heating. He can't change the main fuse anyway - only the supplier can.
Last time I had one uprated, it didn't cost anything, but that's a
while back. It can only be done if the fuse box and associated wiring
is in good condition and already rated for 100A, and the earth/service
bonding is up to current standards.

Obviously pre Part P, but is this normal practice?

Fairly.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

On 22/12/2011 13:12, js.b1 wrote:

Thus you can "overload" a 60A fuse to 90A for an hour or more, at 70A
the fusing time is probably near a day. Sorry can not read my BS1361
fuse chart properly (scan of a photo of a photocopy).

Try that:

http://wiki.diyfaq.org.uk/images/0/06/Curve-BS1361.png

The only exception to this is two 45A showers - but even then both are
not likely to be operating at the same time AND a 90A load will not
blow a 60A fuse that quickly. The fuse above 60A is 80A, some
suppliers will upgrade for a fee. I recall they are downgrading 100A
to 80A for network reasons during routine work.

Indeed - they did that on ours when replacing all the local aerial LV
wiring recently.

--
Cheers,

John.

/================================================== ===============\
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|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 22/12/2011 13:34, David WE Roberts wrote:

"David WE Roberts" wrote in message
...
snip
*The keyword is diversity

Having Googled http://www.diy-forum.net/rating-main-fuse-t50249.html
snip

Blush
Just read the second page and found a well known contributor to this
newsgroup asking very similar questions.
I blame the government.
/Blush

And a similar set of answers as well which should at least be
reassuring. (aforementioned "forum" would appear to be little more than
another of these usenet scraping web front ends - so basically just
uk.d-i-y on the web)


--
Cheers,

John.

/================================================== ===============\
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|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

*The keyword is diversity

Having Googled http://www.diy-forum.net/rating-main-fuse-t50249.html

100% of the biggest break + 40% of the rest
45 + (122*.4) = 93.8

Which suggests that I should have a 100A fuse.

Have you ever blown the 60 Amp fuse at all?..

If and when you do then perhaps is the time to have it changed, if its
failure was from overload.

Also can you afford the power to blow said fuse;!.....


I was chatting to a UK Power networks bloke at a roadside distribution
unit the other month seemed each phase had just a 300 amp fuse on for
supplying the estate, some 100 odd houses so he said...



Next question, what diameter main cable do I need to support this?
[a 60A fuse should not contribute to the lights dimming but insufficient
power through the main feed might]

Might be more to do with how and from where your fed...

--
Tony Sayer

tony sayer wrote:
*The keyword is diversity

Having Googled http://www.diy-forum.net/rating-main-fuse-t50249.html

100% of the biggest break + 40% of the rest
45 + (122*.4) = 93.8

Which suggests that I should have a 100A fuse.

Have you ever blown the 60 Amp fuse at all?..

Yup! :-)

But its not germane to this thread so I'll get my coat..

On Thu, 22 Dec 2011 14:51:04 +0000, John Rumm wrote:

On 22/12/2011 13:12, js.b1 wrote:

Thus you can "overload" a 60A fuse to 90A for an hour or more, at 70A
the fusing time is probably near a day. Sorry can not read my BS1361
fuse chart properly (scan of a photo of a photocopy).

Try that:

http://wiki.diyfaq.org.uk/images/0/06/Curve-BS1361.png

The only exception to this is two 45A showers - but even then both are
not likely to be operating at the same time AND a 90A load will not
blow a 60A fuse that quickly. The fuse above 60A is 80A, some
suppliers will upgrade for a fee. I recall they are downgrading 100A
to 80A for network reasons during routine work.

Indeed - they did that on ours when replacing all the local aerial LV
wiring recently.

Tried to do mine when the meter was changed but I persuaded the chap to
leave in the 100A one.
--
Peter.
The gods will stay away
whilst religions hold sway

On Dec 22, 2:51*pm, John Rumm wrote:
Try that:
http://wiki.diyfaq.org.uk/images/0/06/Curve-BS1361.png

Brilliant, thanks.

Looks like a 60A fuse will blow after 58min at 105A.
Whilst an electric shower, cooker, couple of 2kW fan heaters, dryer,
microwave, lights may be on all at once - not many people will shower
for 58mins continuous.

Interestingly an 80A fuse will hold for 125mins at 130A.
That is two electric showers and rather a lot more, for 125mins...
would not be any skin left after a 125min shower :-)

The only exception to this is two 45A showers - but even then both are
not likely to be operating at the same time AND a 90A load will not
blow a 60A fuse that quickly. The fuse above 60A is 80A, some
suppliers will upgrade for a fee. I recall they are downgrading 100A
to 80A for network reasons during routine work.

Indeed - they did that on ours when replacing all the local aerial LV
wiring recently.

I suspect that may be due to the cost of maintaining a sufficiently
low Ze for a 100A fuse throughout the LV network, although it could
simply be a very rational decision based on the real-world capacity of
an 80A fuse. BS1361 has generous trip limits.

I think the supply cable is typically 35mm with typical 135A rating,
but no idea if that is peak or what. I think the 135A figure is for
PILC when it was used to supply two houses on a loop-in supply. Then I
think one house can be 60A and the other 80A, so perhaps the max
figure is basically just before it turns into molten copper marbles
underground or steam comes up. Loses in LV are about 7%, a rather
considerable amount of global warming... :-D

On 22/12/2011 17:21, PeterC wrote:
On Thu, 22 Dec 2011 14:51:04 +0000, John Rumm wrote:

On 22/12/2011 13:12, js.b1 wrote:

Thus you can "overload" a 60A fuse to 90A for an hour or more, at 70A
the fusing time is probably near a day. Sorry can not read my BS1361
fuse chart properly (scan of a photo of a photocopy).

Try that:

http://wiki.diyfaq.org.uk/images/0/06/Curve-BS1361.png

The only exception to this is two 45A showers - but even then both are
not likely to be operating at the same time AND a 90A load will not
blow a 60A fuse that quickly. The fuse above 60A is 80A, some
suppliers will upgrade for a fee. I recall they are downgrading 100A
to 80A for network reasons during routine work.

Indeed - they did that on ours when replacing all the local aerial LV
wiring recently.

Tried to do mine when the meter was changed but I persuaded the chap to
leave in the 100A one.

Ours gave a rather feeble reason of "he was not sure if the tails were
large enough - they might only be 16mm^2). However we rarely pull more
than 30A so it was a non issue really.

--
Cheers,

John.

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| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

"tony sayer" wrote in message
...
*The keyword is diversity

Having Googled http://www.diy-forum.net/rating-main-fuse-t50249.html

100% of the biggest break + 40% of the rest
45 + (122*.4) = 93.8

Which suggests that I should have a 100A fuse.

Have you ever blown the 60 Amp fuse at all?..

snip

Isn't that a bit like asking "Have you ever had an accident? No? Then why do
you need insurance?"
Blowing the main fuse could be a real disaster in the winter and is
certainly something I would prefer to avoid.

Also, I am planning to have power taken down to the Mother Of All Sheds when
we have the building work done, so I would like to be sure that I have
enough spare capacity.

Fortunately I should be able to trade this off against the electric shower
which will be surplus to requirements once we get the new heating system in.

Cheers

Dave R
--
No plan survives contact with the enemy.
[Not even bunny]

Helmuth von Moltke the Elder

(\__/)
(='.'=)
(")_(")

On 22/12/2011 16:41, tony sayer wrote:
*The keyword is diversity

Having Googled http://www.diy-forum.net/rating-main-fuse-t50249.html

100% of the biggest break + 40% of the rest
45 + (122*.4) = 93.8

Which suggests that I should have a 100A fuse.

Have you ever blown the 60 Amp fuse at all?..

If and when you do then perhaps is the time to have it changed, if its
failure was from overload.

Also can you afford the power to blow said fuse;!.....


I was chatting to a UK Power networks bloke at a roadside distribution
unit the other month seemed each phase had just a 300 amp fuse on for
supplying the estate, some 100 odd houses so he said...

The diversity applied by the suppliers is actually quite surprising...
IIRC they allocate only something like 2kW per household in their
calculations. Still, empirical evidence would suggest they get it right
more often than not, since supply failure at that level seems very rare.

(which might be down to their choice of cable sizes - by keeping them
small they transmute overload problems for their supply into undervolt
problems for the consumer!)


--
Cheers,

John.

/================================================== ===============\
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| John Rumm - john(at)internode(dot)co(dot)uk |
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js.b1 wrote:

The fuse above 60A is 80A, some
suppliers will upgrade for a fee. I recall they are downgrading 100A
to 80A for network reasons during routine work.

When I moved into this house, the cut-out was fused at 60A and all meter
tails were 16mm^2, When I replaced the C/U I upgraded the tails to
25mm^2, the meter was recently replaced and the chap upgraded the
suppliers cabling from cut-out to meter with 25mm^2 and upgraded the
fuse to 80A without being asked.

Andrew Gabriel wrote:
In article ,
"David WE Roberts" writes:
*The keyword is diversity

Having Googled http://www.diy-forum.net/rating-main-fuse-t50249.html

100% of the biggest break + 40% of the rest
45 + (122*.4) = 93.8

I regard this recommendation as out of date now.
It applied when everyone had 1 ring circuit, 1 lighting circuit, etc.
I generally install several of each now, so that any problems with one
are limited in scope, particularly when using RCBOs.

That doesn't mean
that because my house has 4 ring circuits, it will be drawing any more
power than when it had just one.

You have to apply diversity to the diversity rules when there are 4 ring
circits in a house:-)

I can count on one hand the number of times I have seen a blown main fuse
(and I have a normal number of digits). Fuses do age with time and that
probably accounted for most of the failures.


--
Adam

On 22/12/2011 17:40, js.b1 wrote:
On Dec 22, 2:51 pm, John wrote:
Try that:
http://wiki.diyfaq.org.uk/images/0/06/Curve-BS1361.png

Brilliant, thanks.

If you search the wiki for "fuse" and "mcb" you should be able to find
decent scans of all the common trip curves. Just click on the graph to
get a bigger version.

Looks like a 60A fuse will blow after 58min at 105A.
Whilst an electric shower, cooker, couple of 2kW fan heaters, dryer,
microwave, lights may be on all at once - not many people will shower
for 58mins continuous.

Interestingly an 80A fuse will hold for 125mins at 130A.
That is two electric showers and rather a lot more, for 125mins...
would not be any skin left after a 125min shower :-)

Yup, 125 mins in the shower does seem a little OTT (well on your own
anyway! ;-)


--
Cheers,

John.

/================================================== ===============\
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| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 22/12/2011 11:43, David WE Roberts wrote:
My main fuse is rated at 60 Amp/500V.


Excuse my ignorance, but if it is rated at 60A at 500V, then that is 30
kW, therefore at 230V it is therefore 130A isn't it?

--
Toby...
Remove pants to reply

Toby wrote:

On 22/12/2011 11:43, David WE Roberts wrote:
My main fuse is rated at 60 Amp/500V.


Excuse my ignorance, but if it is rated at 60A at 500V, then that is 30
kW, therefore at 230V it is therefore 130A isn't it?


No.

it means it is designed for 60A continuous max current of 60A and designed
to break a supply of upto 500V, which is related to both the insulation of
the fuse body and the ability to quench the arc caused by the fuse blowing
under load.

eg if that fuse blew while carrying 10kV, it would do sod all as the arc
would just carry on burning across the fuse ends. Hence higher voltage fuses
tend to be longer.

Power has no meaning with respect to fuses.

Cheers

Tim
--
Tim Watts

In article ,
Toby wrote:
On 22/12/2011 11:43, David WE Roberts wrote:
My main fuse is rated at 60 Amp/500V.


Excuse my ignorance, but if it is rated at 60A at 500V, then that is 30
kW, therefore at 230V it is therefore 130A isn't it?

no - those are simply maximum for each unit.

--
From KT24

Using a RISC OS computer running v5.16

On 23/12/2011 09:44, Tim Watts wrote:
Toby wrote:

On 22/12/2011 11:43, David WE Roberts wrote:
My main fuse is rated at 60 Amp/500V.


Excuse my ignorance, but if it is rated at 60A at 500V, then that is 30
kW, therefore at 230V it is therefore 130A isn't it?


No.

it means it is designed for 60A continuous max current of 60A and designed
to break a supply of upto 500V, which is related to both the insulation of
the fuse body and the ability to quench the arc caused by the fuse blowing
under load.

eg if that fuse blew while carrying 10kV, it would do sod all as the arc
would just carry on burning across the fuse ends. Hence higher voltage fuses
tend to be longer.

Power has no meaning with respect to fuses.

Cheers

Tim

Ahh yes, I see, thanks :-)

--
Toby...
Remove pants to reply

Toby wrote:

On 23/12/2011 09:44, Tim Watts wrote:
Toby wrote:

On 22/12/2011 11:43, David WE Roberts wrote:
My main fuse is rated at 60 Amp/500V.


Excuse my ignorance, but if it is rated at 60A at 500V, then that is 30
kW, therefore at 230V it is therefore 130A isn't it?


No.

it means it is designed for 60A continuous max current of 60A and
designed to break a supply of upto 500V, which is related to both the
insulation of the fuse body and the ability to quench the arc caused by
the fuse blowing under load.

eg if that fuse blew while carrying 10kV, it would do sod all as the arc
would just carry on burning across the fuse ends. Hence higher voltage
fuses tend to be longer.

Power has no meaning with respect to fuses.

Cheers

Tim

Ahh yes, I see, thanks :-)


There is another element too.

While you have an arc (which is why all but the tiniest of fuses are filled
with powder, and massive substation breakers are filled with oil), you have
a voltage drop along with a flowing current through the arc. This lasts for
a certain amount of time, which is a funtion of the fuse characteristic and
the amount of current flowing.

The powder (or oil) helps quench the arc, but it has another role too.

Simple application of E=VIt integrated means that to blow under a fault,
there will be some energy imparted in the fuse body which ultimately = heat.

This is why higher voltage and higher current fuses tend to be fatter (100A
fuse wire is still pretty thin, no need for a 10mm dia fuse body to contain
it at first sight). The more energy given up means the more thermal-mass
buffer you need to avoid bad things like the fuse exploding.

There's another parameter that is related to this too - the "rupture
capacity". A tiny fuse in a small transformer powered alarm clock can never
see much short circuit current.

A dead short on a pair of meter tails with the substation in your back
garden means a failt current of several thousand amps burning in the arc in
the fuse. Even if the fuse blows in a few tens of milliseconds, that still
equates to quite a large number of joules.



--
Tim Watts

On 23/12/2011 13:35, Tim Watts wrote:
Toby wrote:

On 23/12/2011 09:44, Tim Watts wrote:
Toby wrote:

On 22/12/2011 11:43, David WE Roberts wrote:
My main fuse is rated at 60 Amp/500V.


Excuse my ignorance, but if it is rated at 60A at 500V, then that is 30
kW, therefore at 230V it is therefore 130A isn't it?

A dead short on a pair of meter tails with the substation in your back
garden means a failt current of several thousand amps burning in the arc in
the fuse. Even if the fuse blows in a few tens of milliseconds, that still
equates to quite a large number of joules.

Agreed. Just to add a general note that the substation in the back
garden thing, can be an issue for any circuit breaker really. It is
possible to get scenarios where even a normal socket close to the CU in
those cases, could have a fault current well in excess of what even the
MCBs in the CU can interrupt (usually capped at 6kA, but sometimes 10kA).


--
Cheers,

John.

/================================================== ===============\
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| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

Also can you afford the power to blow said fuse;!.....


I was chatting to a UK Power networks bloke at a roadside distribution
unit the other month seemed each phase had just a 300 amp fuse on for
supplying the estate, some 100 odd houses so he said...

The diversity applied by the suppliers is actually quite surprising...
IIRC they allocate only something like 2kW per household in their
calculations. Still, empirical evidence would suggest they get it right
more often than not, since supply failure at that level seems very rare.


Matey from UK power networks told me that fuses mainly fail due to olde
age rather than overload!...

--
Tony Sayer

On 24/12/2011 12:48, tony sayer wrote:
Also can you afford the power to blow said fuse;!.....


I was chatting to a UK Power networks bloke at a roadside distribution
unit the other month seemed each phase had just a 300 amp fuse on for
supplying the estate, some 100 odd houses so he said...

The diversity applied by the suppliers is actually quite surprising...
IIRC they allocate only something like 2kW per household in their
calculations. Still, empirical evidence would suggest they get it right
more often than not, since supply failure at that level seems very rare.


Matey from UK power networks told me that fuses mainly fail due to olde
age rather than overload!...

Yup, can well believe that...


--
Cheers,

John.

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