Why didn't the fuse blow?

[The Medway Handyman]

Swmbo made some homemade bacon & lentil soup today & I got the job of blending it.

We've got a Breville blender

rubber washer which seals the blade assembly into the base of the jug has always been a bit flakey, allowing a tiny amount of soup through, but today it decided to leak like mad, soup all over the blender & worktop.

To my surprise the blender became live, obviously the liquid had come into contact with an electrical part. The soup spilt on the worktop was also live, I got shocks from both. Had to unplug the bugger rather quickly.

Fortunately I was still wearing my safety boots at the time and 230v shocks don't really affect me that much for some reason.

Its going in the bin & a new one will be purchased, but I wondered? Why didn't the fuse blow?

We have the older style fuse box with re wireable fuses & no RCD - would that have tripped?

[Dave Plowman (News)]

Because not enough current flowed to cause this. You only need a tiny amount of current to kill you.

If the current flow was dangerous - yes. They work on milliamps rather than amps.

[John Rumm]

Never mind tobasco, that could pep it up a bit ;-)

Prolly because you have never had one while in in contact with a good earth!

Because the soup was not a good enough conductor to pass the 20 - 30 amp required to open the fuse quickly.

Without a doubt. Probably long before the soup got right out of the blender.

[Nige Danton]

If I recall correctly the fuseable link in a re-wirable fuse needs about 2 and half times its rated current carrying capacity before it will blow whereas an MCB needs about one and half times. You should think about having an RCD fitted. Have a split consumer unit fitted with the lighting circuit and maybe the freezer on one unprotected side and everything else including sockets and external power off the other side and protected with an RCD. Heaps better.

-- Nige Danton

[Mike Dodd]

As others have said - not enough current flow to blow the fuse (you see, less salt in your food IS more healthy!)

For what it's worth -

The soup may have shorted across Live/Neutral on the innards of the blender, in which case there would be current flow through this. This is unlikely to blow any substantial fuse (say 30A for ring). What's likely to happen is that the current flow will heat-up, burn, dry-out the wet-short, possibly with smoke, almost certainly with smell, until the short self-heals (water evaporates/boils away) leaving a non-conductive lentil and bacon substrate.

...or... the lethal concoction (no disrepect to Mrs Medway) may have contacted Live only, in which case there's no current flow at all between Live and Neutral, and no fuse/mcb in the world will protect against this. Until some helpless soul provides a current path down to earth by shoving fingers in now-live soup. In this scenario, a protective device that detects an imbalance in current flow between Live and Neutral (i.e. current leaking to earth) - an RCD (others exist, but keep it simple) would trip once the leakage current exceeds a predefined limit - typically 30mA.

Just for interests sake, from memory - the figures will be wrong, but in the right sort-of magnitude, in terms of current flow through the body I was taught 1-5 mA = feel sensation, 10mA+ = painful, 50mA = potentially lethal. These levels are a long way away from the rupture current of a fuse.

Mike

[Rod]

New toy time!

Hmmm, no 24V LiIon SDS models? When will Makita and Ryobi take on the kitchens of the world?

In all seriousness, I much prefer a stick blender (albeit one that cost less than £30) to a liquidiser for soup. Major reason is that you don't have to pour soup from pan to goblet to pan which is messy, dangerous (if soup is hot - or if it leaks out ...) and leads to excess washing up. Also liquidisers seem to make the soup somewhat frothy and there never seems to be a time at which you can leave it 'slightly bitty/lumpy' - which I prefer to 'totally homogenised'.

[Rod]

PS If you decide you do want a liquidiser-style blender, we have been happy enough with the Philips HR2094. Goblet is heavy (glass). Works well.

Has soup redirecting rim on the top of the base where the goblet fits. :-)

[Ian White]

Dave, Dave... pry your fingers open and spend some of the profits on a CU! We don't want to lose you, or Mrs Medway either.

[Clint Sharp]

In message , The Medway Handyman writes

Yummy.

Are you sure you haven't missed a birthday, anniversary etc. or failed to notice a new haircut?

RCD would have tripped, the amount of current needed to rupture a fuse is massively higher than the current needed to feel the shock.

More importantly, did the soup survive, how was it?

[Dave Liquorice]

I'd assume that this is blender was plugged into a ring protected by a 30A bit of fuse wire. That will pass 30A pretty much indefinately. To make it blow in a few seconds you're going to need double or treble that so lets say 100A. 100A @ 230v is 23kW, that would have made the soup boil rather quickly and quite a big BANG/FLASH! B-)

MCBs have both thermal and magnetic trip mechanisiums. The thermal side deals with overlaods only just above the rated capacity and the magnetic with gross overloads. The thermal inertia of the the thermal part is to slow to trip in the specified time with gross overloads. Wired fuses are terribly slow, a "30A" fuse will pass 40A for maybe days or at least hours. It'll get hot and could present a fire risk but possibly never hot enough to melt and rupture.

The RCD would probably have tripped when the soup first made contact with live parts and most definately within the first cycle or two of the first shock Dave got.

[dom]

Medway Handyman invents world's first high-temperature superfluid:

"It requires a precise ratio of legumes to finely-divided porcine remnants" said the Medway Handyman.

[The Medway Handyman]

Oh yes! Stock from Sundays gammon, onions, bacon, lentils. SWMBO trained as a chef.

LOL. No, and the insurance is all paid up to date.

Haven't tried it yet, its in the flask for lunch along with homemade rolls.

[mark.hannah]

Perhaps you have developed some kind of super-hero ability that makes you resistant to electricity? Been bitten by any spiders recently? ;-)

[Invisible Man]

........Snip

Usually best not to put the rolls in the flask

[John Rumm]

Indeed - but I was thinking of the fuse in its plug, rather than the whole circuit (a 30A rewireable will take something like 450A to open "instantly", it could take over a minute even with nearly 90A flowing)

For certain values of "only just". A 32A type B MCB will probably carry

45A indefinitely. (in fact, up that end of the curve the response from a MCB is not that different to that of a rewireable fuse)

[dennis]

I agree, I bought a rechargeable cordless stick blender for £6 in a clearance, really good if a bit heavy with a bigger battery pack than most drills.

[dennis]

I'm not susceptible to shocks either.. found that out when I was a kid after I dropped an extension into an aquarium and wondered why it was difficult to reach in and pick it up. It tingles when you first put your hand in and gets strong the closer you get.

[Kevin]

that's a bit miss leading and bollocks,wet both hands hold onto a live cable in one hand and the neutral in the other (& post the video on youtube) and I will guarantee you are not immune from shocks, oh and write your will before hand

[The Natural Philosopher]

RCD would have tripped, yes.

No reason to blow any other fuse, since the thing was not drawing excess current.

It probably wasn't earthed somehow. THAT bears investigation.

[Kevin]

if its double insulated it wont be