On Friday, 14 November 2014 11:31:32 UTC, wrote:
On Thursday, November 13, 2014 4:29:31 PM UTC, whisky-dave wrote:
On Thursday, 13 November 2014 14:23:05 UTC, Chris French wrote:
In message ,
whisky-dave writes
On Thursday, 13 November 2014 08:31:32 UTC, Chris French wrote:
In message , PeterC
writes
On Wed, 12 Nov 2014 19:54:50 +0000, Lawrence wrote:
My house had a 60A fuse on the incoming cutout. I rang Western Power
to enquire about an upgrade and within 90 minutes it was done. I now
have 80 amp fuse and was told it could go up to 100 amp if the cutout
was changed. Incredible service.
The question though. What current fuse is normal these days?
When my meter was changed about 3 years ago the chap wanted to put in a new
80A fuse in place of the 100A; I persuaded him to fit a new 100A instaead.
Seems that there might be a desire to /reduce/ load - I wonder why.
Unlikley I'd have thought.
how many people consider the rating of their main fuse when using their
electrical devices,
I have been, in fact last night I 'installed' a new energy meter
http://www.amazon.co.uk/Efergy-Wirel...e-Compatible/d
p/B0074HN5HW/ref=sr_1_1?ie=UTF8&qid=1415879304&sr=8-1&keywords=energy+mo
nitor+e2
as the previous one from npower died.
My fuse says 60 amps, ~ 14.4KW
my water heater cyclinder 3KW
2 storage raidaitors about 2.4KW each.
1 ex storage raidaitor (not removed was 3.4KW)
-----------------------
An electric cooker 2-3KW depending on what's used.
1 bathroom heater ~2kw
2 convector heaters about 2KW each.
So when my CH was first switched on the total would be
3+4.8+3.4 =11.2KW
so in theory without any lights on and switching on my kettle
I get to almost 60A or 14.2KW.
With a TV and 2 computers it doesn't leave me much headway if any.
I exceeded 11.5KW last night at about 12:30am, as I was testing the
alarm function of the energy unit.
Think I'll set my alarm for 13KW
Well, I knew posting that here would get people out of the woodwork :-)
In reality it's unlikely that all those things will be on at the same
time I'd have thought. eg storage heaters are normally timed to come
overnight. and things that are on won't necessarily be drawing current,
if they are thermostat controlled. Things like kettle probably wouldn't
make a difference anyway as they are on for such a short amount of time.
But in a sense that shows how hard it is to draw anywhere near the max
current, especially for any length of time. You need to be using
multiple high load devices to do that.
and when was the last time you heard of someone
blowing their main fuse?
Personally never, but I've not personally known anyone to die from an
electric shock.
I'm not sure exactly when such a fuse will blow, or rather at what
precise current as that varies with time and temperature.
Might make an intresting practical lab.
I imagine they will continue to draw a bit more than the rated current
for sometime
--
I prefer not to waste my imagination on such things, I have far better use for imagination than thinking of fuses ;-)
But I would like to find out.
earlier this week I ordered 50 20mm 1amp fuses. pleanty to experiment on.
Your fears are unfounded. 20mm fuses behave quite diifferently to incomer fuses
Fears of what exactly....
As for teh fuses they are for a lab we run. We get the studetn to undersaqtnd that even an 1.5V battery has 'power' we get them to short it out to blow a fuse. In the book we are using it states use a 3 amp car fuse.
I tried that and the fuse did not blow, so a useless sort of experiment that would have proved little. So I decided to get 1 amp 'normal' for the lab fuses of 1 amp. These can be seen to blow too.
Now considering a 11.5V AA (alkaline) on short circuit these batteries can supply 3.6 amps as measured, so why don't they blow a 3amp fuse ?
I had a pretty good idea, students, well they are here to learn.
So if they have any real interest in their results thay might just ask why a fuse rated at 3 amps doesn't blow when 3 amps are passed through it ?
I intend to given them some clues, both theory and in practice.
My intention is also to get them to learn how to cut and strip a piece of wire, where as some academics prefer us to buy quantities of pre-prepared leads, i.e stripped and ready for use in a box.
I believe the basics should be clearly taught & understood, a couple of years ago I felt embarressed when a final year student that had been awarded a degree in electronic engineering came up to me saying his coil wasn;t working.
He had nailed a coil of enammled copper wire to a board and annouicned he didn;t know copper conducted, after he put a metal, nail through the coil.
But why shoudl I worry, he'll probbly get a managment tube in a power plant.
Or perhaps he'll design the next wind turbin as that was his final year project !.