Multi-headed mains cable

You mean Mr Russ Andrews has mislead me?!

 

I've an RCD on my consumer box Anex – but that's missing the point!

With conventional aftermarket mains leads the plug fuse can be replaced by a fuse of correct rating (given by the manufacturer of the equipment or calculated using the formula I = P / V) if a 13 amp plug fuse is supplied fitted.

A 13 amp fuse is only needed if a piece of kit has a nominal power consumption comparable to a washing machine on spin cycle!

In this case of a 'hydra' configuration (sorry used the name again!) this cannot be done because the plug fuse required is based on sum power consumption and is therefore incorrectly fused for individual equipment.

 

Yeah I know that but people, such as the afore mentioned Russ sell mains cables with, and encourage people to use them with 13A fuses, in a sense rendering the plug fuse useless.

 

Go on then -- yes you have a point - can we have our ball back now?

I think your sense of humour circuit is more likely to burst into flames.

 

Yep ventricular fibrillation is f**kin hilarious – guaranteed to put a permanent grin on yer face!

 

Indeed

Errrm. 2 Amps at 230 Volts is 460 Watts

How many CD players, tuners, etc. do you know that draw 460 Watts?

Most will only draw a tenth of that or less

 

Waaaaahhhhhh!!

Think of the total current draw the mains plug see's technobear mate when connected to five pieces of equipment. This necessitates a 13 amp plug fuse – all of the power to supply all five pieces of equipment needs to flow through this fuse.

Thus at the point of switching on should a CD player, tuner etc develop a fault there is no fuse failsafe – the rating of the 13 amp plug fuse being to high.

Indeed it is for precisely the reason you point out that hi-fi kit almost invariably needs to be fused with a 3 amp or 5 amp fuse!

 

Sorry old bean but you are not correct. I have just looked at the back of my CD player and it says "POWER CONSUMPTION 32 Watts MAX". That's 0.13 Amps.

Assuming that the typical tuner, record deck, etc. is about the same, then four of them would draw 0.52 Amps.

If we then add an integrated amp, a typical 50 Watt per channel example would draw a maximum of some 200 Watts which is 1.25 Amps.

That gives a total of 1.77 Amps. That little lot can easily be catered for by a single 3 Amp fuse.

If we doubled the amplifier power to 100 Watts per channel then we might, on occassions when we are really caning the system, exceed 3 Amps. In that case a 5 Amp fuse will do the job just as well. Any fault in a component that is capable of causing a 3 Amp fuse to blow will certainly also cause a 5 Amp fuse to blow and the time difference between the two will be very small.

 

Your numbers are absolutely correct Chris for the given equipment spec's and I could come up with another set of numbers demonstrating higher current draw using another set of equipment spec's – but this is still missing the point!!

The fuse in the mains plug will not be incorrect for any set of figures because it is referenced to the total current draw and not, as it should be, referenced to the current draw of the individual equipment.

Think in terms of Kirchoffs law; the sum of the currents entering a node must equal the sum of the currents leaving the node.

 

If I put all the items from the above example on a hydra, I would use a 3 Amp fuse.
If I gave each item its own lead, each would have a 3 Amp fuse.

In either case, each item of kit is protected by a 3 Amp fuse!

 

Sounds good on paper Chris. And I assume it would work in practice.

My basic tenet remains however. It's safer to use the fuse recommended by the manufacturer in the configuration intended for the reason one cannot assume to know more than the engineer who designed the equipment in terms of actual operating current draw and possible fault condition.

And neither can those who market mains cables of this configuration.

(And that's not to mention the aftermarket mains cables I've seen come fitted with a 13 amp fuse anyway!).

 

Sorry, I'm being a bit slow here aren't I? This is a wind-up!

Well done. You had me going there :lol:




ps. The fuse is there to protect the circuit as much as the appliance. Just in case anyone is still worried, the only benefit of fitting a 3 Amp fuse is that you can run a thinner cable from the wall socket to the appliance. Since all after market mains cables are capable of carrying the full 13 Amps, a lesser rated fuse is unnecessary.

 

The fuse isn't there to protect you from electrocution. It only takes around 10mA to cause muscle contractions, and IIRC around 30mA to kill you (if applied in the correct manner), so most fuses are hopeless for this purpose.

Not quite - most IEC plugs/sockets are only rated to 10 Amps.

Heath

 

This is patently not the case. A lesser rated fuse is almost always necessary should a 13 amp plug fuse be supplied with an after market hi-fi mains cable. The reasons why can be found on any fire safety website.

Correct. And several thousand milliamps does an even better job! The fuse does not protect against electrocution but does lessen the chance of this proving fatal.

 

Im sure the relevant british standard can give a better discription than a general fire safety website. BS1363 states that the fuse needs to be of a correct rating to protect the flexible cord and appliance it supplies. No mention of electrocution.

 

Now it becomes an argument of semantics and meaning. The fuse is designed to protect the flexible cord and the appliance it supplies. But why do you suppose this is?

Is it because the equipment is valuable or is it because any number of over-current fault conditions are potentially dangerous - or can cause potentially dangerous situations to arise?

Besides which I don't give a monkeys anymore!

:gould:

 

No, chances are you'll be dead well before the fuse blows. There are measures you can take to reduce the threat of a fatal electrocution, but putting a smaller fuse in the plug isn't one of them.

Heath

 

I'm not talking about using a smaller fuse rather using the correct fuse given the power consumption of the kit. Common sense dictates a fuse of the correct rating, given the power consumption of the kit, is more likely to open in the event of over-current faults than one that is too large.

Thus a 30mA fault may not cause a 3 amp fuse to open but a 3000mA fault would. The same is not true if a 13 amp fuse is being used where a 3 amp fuse is appropriate – consequently a reduction in the risk of electrocution through using the correct rating of fuse.

30mA is likely to prove fatal (depending on a number of other factors) 3000mA many times more so.

And I ain't mentioning the fu** word again!

 

It all depends on where the current goes. 30mA or 3A through your heart is very bad. There are no degrees of being dead - it's a binary condition

Heath

 

only 10 types of people understand binary.