fuse upgrade

[GaryMo]

A 30A BS3036 fuse will take 60A for 100s and 50A for in excess of 10000s (2hrs 46mins) before rupturing.

 

[RF Lighting]

At a guess I'd say 1 in every 10 houses I visit in my local area still have this type of cutout.

I only can think of one which the fuse has blown due to overload.

 

[sajeel]

Thank you to RF Lighting and others who have been helpful, yes they are cast iron 30A fuses split into two one for property next door.

 

[ColJack]

Dont these things blow quite often with such a low current rating?

I was told that when designing a supply for an estate, they only allow 16A per house.. now that's some diversity for you....

if you think about it.. the largest things in your house will bw the cooker and showere, both of which aren't likely to be on full load for any protracted period of time.
next is any electrical heating appliances such as the immersion heater.. again, once up to temp this will cycle on and off, same for normal heaters..
I suppose the washing machine and dishwasher would be next on the list, but unless you wash clothes all day long and run the dishwasher after every cup of tea, then again, those aren't on the heating bit for long..

 

[GaryMo]

if you think about it.. the largest things in your house will bw the cooker and showere, both of which aren't likely to be on full load for any protracted period of time

The shower is very likely to be on full load whilst it's being used.

 

[Aragorn84]

well yes, but its on for what 15-20mins, which is what coljacks point entailed?

Its interesting that a 30A fuse will happily allow such a high amount of current past for such a long period of time without blowing!

Is that the same type of fuse that would exist in an old rewirable fuse box (like the one fitted in this property)?

I presume they work on the principle that a bad short is likely to draw many times the rating and blow it immediately, but surely its there to protect the feed cable, and if you can push 50A thru it for quite a while that could cause damage to the 30A feed wire (or for example the 2.5mm T&E in a domestic ring)?

 

[GaryMo]

What im getting at is that a cooker is thermostatically controlled, unlike a shower.
However, consideration should be given to the size and type of supply before installing such items.

 

[ColJack]

some showers have 2 power settings, so they could also be used on the lower setting..

 

[GaryMo]

Mine has 2 settings but to get a decent amount of heat at any time other than the summer months you need to reduce the water flow so much that its not worth having.

 

[chapeau]

and if you can push 50A thru it for quite a while that could cause damage to the 30A feed wire (or for example the 2.5mm T&E in a domestic ring)?

2.5mm2 copper in free air can probably take as much as 200amps before it melts. Obviously when packaged as T/E it would melt it's pvc sheath before then, but the maximum current carrying figures you get in tables found in electrical regulations have quite a bit of headroom in them too.