Help please. "Kettle" lead fuse advice

[Alec]

[quote name='4stringslow' timestamp='1469801522' post='3101177']So, for most** UK kettle leads it's ok to use a 13A fuse.
[/quote]
If it's a kettle lead, then you'll need a 13A fuse, as most kettles are around 2,500W, and so will draw more or less the full 13A.

If, as others have observed, it's an IEC lead (as it will be for supplying kit), then all of the previous posts make it clear that IEC connectors have a 10A rating, but may be fused at 13A. And, in practice, that makes the most sense for a generic set of IEC leads. After all, they will be swapped between different bits of kit, which puts lower fuse ratings at much more risk of being blown.

[taunton-hobbit]

I, being mega-technical, tend to make sure that any gig leads
have a 5amp fuse - its worked for fifty years, so I'm not stopping now.

[bassace]

[quote name='taunton-hobbit' timestamp='1470334573' post='3105281']
I, being mega-technical, tend to make sure that any gig leads
have a 5amp fuse - its worked for fifty years, so I'm not stopping now.


[/quote]

And me too. I can't justify this technically but it just seems to make sense. Fifty years for me too.

[Dad3353]

[quote name='bassace' timestamp='1470337514' post='3105313']
And me too. I can't justify this technically but it just seems to make sense. Fifty years for me too.
[/quote]

I concur with all these [s]old folks[/s] seniors (well, I would, wouldn't I..?), although, here in [s]the real world[/s] Europe, there are [i]no [/i]fuses in these leads, so it's all a bit dumb as a debating subject, really. The leads don't often explode or catch fire over here; I must have handled thousands of 'em over the decades. Ne'er a jot of trouble with 'em regarding fuses.

[taunton-hobbit]

It's the 'often' that's got me worried...........

[Grangur]

[quote name='taunton-hobbit' timestamp='1470334573' post='3105281']
I, being mega-technical, tend to make sure that any gig leads
have a 5amp fuse - its worked for fifty years, so I'm not stopping now.


[/quote]

Ahhh, but what you're missing is that there must be discrimination between the fuse in the lead and the fuse in the amp. That is to say that if there is a fault in the amp, the 3amp fuse inside the amp must blow before the one in the lead (designed to protect the lead) even gets excited enough to even think about blowing. (There's a technical term for this, but i can't remember and I can't be arsed)

There, that's enough to add to the confusion!

[stingrayPete1977]

[quote name='Dad3353' timestamp='1470337902' post='3105321']


I concur with all these [s]old folks[/s] seniors (well, I would, wouldn't I..?), although, here in [s]the real world[/s] Europe, there are [i]no [/i]fuses in these leads, so it's all a bit dumb as a debating subject, really. The leads don't often explode or catch fire over here; I must have handled thousands of 'em over the decades. Ne'er a jot of trouble with 'em regarding fuses.
[/quote]

The general feeling in the UK is that we use fused plugs due to our love of the '30 amp ring main' where a 16 amp radial circuit is more common in mainland Europe, in reality a 16 amp MCB in the consumer unit would trip far sooner than a 13 amp fuse in a plugtop would blow.

I've been on building sites where they have a cement mixer, radio, kettle, sandwich toaster and a nest of battery chargers all on at the same time all on a 25 metre ext reel!

[Grangur]

[quote name='stingrayPete1977' timestamp='1470087617' post='3103253']
My musings are more in response to this to be honest mate, you cant just look at the wattage (900watt in this case) without looking at the voltage, the example above probably takes a fraction of the input wattage suggested.

You can have many more watts out than you put in, but they are at a reduced amperage, the power to move a paper cone isn't much compared to say an electric motor, in that case you might need to reduce the voltage to the point that the input at 3000 watts now only drives a 300 watt motor.
[/quote]

This could be due to high levels of charge being stored in capacitors in the device, being discharged in bursts higher than the mains could supply. In the case of a welder, striking an arc will take a high current, but you don't keep that going for a prolonged period - usually only seconds.

In an amp you may hit peaks of high output, but again, the high amplitude doesn't keep going ALL the time - otherwise your VU meter would simply sit on the red-line and never come down.

[Grangur]

[quote name='stingrayPete1977' timestamp='1470338811' post='3105335']
The general feeling in the UK is that we use fused plugs due to our love of the '30 amp ring main' where a 16 amp radial circuit is more common in mainland Europe, in reality a 16 amp MCB in the consumer unit would trip far sooner than a 13 amp fuse in a plugtop would blow.

I've been on building sites where they have a cement mixer, radio, kettle, sandwich toaster and a nest of battery chargers all on at the same time all on a 25 metre ext reel!
[/quote]
What Pete isn't telling you is that they keep their feet warm on the windings of the said extension lead.

[4stringslow]

[quote name='taunton-hobbit' timestamp='1470334573' post='3105281']
I, being mega-technical, tend to make sure that any gig leads
have a 5amp fuse - its worked for fifty years, so I'm not stopping now.


[/quote]

Fair enough, just understand that it's really not necessary and that a 13A fuse is perfectly fine.

If you lived in France or Germany or any other European country your mains lead wouldn't even have a fuse.

[taunton-hobbit]

Most (all?) of my amps/kit seemed to have 3a internal fuses - I've always used 5 as a catch-all (works for me)

[stingrayPete1977]

[quote name='Grangur' timestamp='1470339029' post='3105341']

What Pete isn't telling you is that they keep their feet warm on the windings of the said extension lead.
[/quote]

Well the only other way to keep warm is to do some work, we can't have that can we?!

[4stringslow]

[quote name='Grangur' timestamp='1470338947' post='3105338']
This could be due to high levels of charge being stored in capacitors in the device, being discharged in bursts higher than the mains could supply. In the case of a welder, striking an arc will take a high current, but you don't keep that going for a prolonged period - usually only seconds.

In an amp you may hit peaks of high output, but again, the high amplitude doesn't keep going ALL the time - otherwise your VU meter would simply sit on the red-line and never come down.
[/quote]

Yes, capacitors can certainly provide a peak of power but they are only discharging energy they have previously absorbed, so the average power output cannot exceed the average power input.

Imagine a tap filling a bath. You can let the tap run constantly into the bath or you could repeatedly let the tap run into a bucket and then empty each full bucket in one great whoosh into the bath. Which method would fill the bath the fastest?

The bucket may be able to supply a greater flow of water than the tap, but only for a short period of time. On average, the bucket cannot possibly supply more water than the tap.

[Grangur]

[quote name='4stringslow' timestamp='1470340463' post='3105378']
Yes, capacitors can certainly provide a peak of power but they are only discharging energy they have previously absorbed, so the average power output cannot exceed the average power input.

Imagine a tap filling a bath. You can let the tap run constantly into the bath or you could repeatedly let the tap run into a bucket and then empty each full bucket in one great whoosh into the bath. Which method would fill the bath the fastest?

The bucket may be able to supply a greater flow of water than the tap, but only for a short period of time. On average, the bucket cannot possibly supply more water than the tap.
[/quote]
Oh I appreciate all that. But what I'm saying is if you fill the bath at a rate of 15 litres a minute (100w) you can still discharge at 150 litres a minute (900W) out of the plug provided you've got a big enough plug hole and pipe to let the water fall out fast enough.

[4stringslow]

[quote name='taunton-hobbit' timestamp='1470340169' post='3105362']
Most (all?) of my amps/kit seemed to have 3a internal fuses - I've always used 5 as a catch-all (works for me)


[/quote]

Yes, but a mains lead is (almost) universal and can be used on any item of equipment with the same mains connector, so the technically correct fuse is one that can supply the maximum safe power through the mains lead. In the UK this is 13A. There are no advantages in using a lower rated fuse, only disadvantages. As you rightly say, your amp already has the correct fuse for its own requirements.

[4stringslow]

[quote name='Grangur' timestamp='1470340821' post='3105385']
Oh I appreciate all that. But what I'm saying is if you fill the bath at a rate of 15 litres a minute (100w) you can still discharge at 150 litres a minute (900W) out of the plug provided you've got a big enough plug hole and pipe to let the water fall out fast enough.
[/quote]

True, but that's just a larger scale example of my bucket one. You can only provide that 900W for a short burst before going back to 100W and even then you'll have to reduce the discharge to something less than 100W in order to refill the bath before you can discharge another burst of 900W. And if you work out the average discharge over a period of time you'll find it can never exceed 100W.

[stingrayPete1977]

I fitted a frequency inverter a couple of years ago, it is a massive battery that charges at 50hz then discharges at 60hz, works just like the bath idea but as you say you cant run it forever.

[grandad]

I use 5A fuses in all my kettle leads. 10A/13A I use only for mains extention leads.

Useful fuse rating table:

13A - 3000W
10A - 2400W
5A - 1200W
3A - 700W

Mains flex should always be fused wrt the csa of the cable:

mm2
1.5 - 15A - 3600W
1.25 - 13A - 3120W
1.0 - 10A - 2400W - most Euromain/IEC cold connector type C13 or kettle leads.
0.75 - 6A - 1440W
0.5 - 3A - 720W

But it's difficult to gauge the csa just by looking and more often than not a 10A cable is fused at 13A, (apparently this is acceptable practice where short kettle leads are used, 2m or less I think.

Some low power devices tend to blow 3A fuses due to the surge current at switch on so need a 5A rather than 3A.

All electric devices put out less power than is put in over time. They are less than 100% efficient and power is lost mainly in the form of heat.

An amplifier rated at say 70W at the mains input can temporarily store up electrical energy and deliver say 250W output to the speaker but only in short bursts. Over time the output would be less than 70W.

A useful page: [url="http://www.leadsdirect.co.uk/technical-library/mains-wiring/iec-connectors/"]http://www.leadsdire...iec-connectors/[/url]

Look out for those low current fig 8 leads and cloverleaf, 3A max fuse I guess would be ok.

It's good to have electrical safety posts from time to time.

Edited August 5, 2016 by grandad

[Grangur]

[quote name='4stringslow' timestamp='1470340463' post='3105378']
Yes, capacitors can certainly provide a peak of power but they are only discharging energy they have previously absorbed, so the average power output cannot exceed the average power input.

Imagine a tap filling a bath. You can let the tap run constantly into the bath or you could repeatedly let the tap run into a bucket and then empty each full bucket in one great whoosh into the bath. Which method would fill the bath the fastest?

The bucket may be able to supply a greater flow of water than the tap, but only for a short period of time. On average, the bucket cannot possibly supply more water than the tap.
[/quote]Yes, I know and I agree.

In all these examples though, you won't blow the fuse in the primary circuit. All that will happen is the secondary circuit will run out of juice.

With an amp you'll see it will be rated as 900W Max RMS output. This doesn't mean it's giving 900w ALL the time. 900w is when the VU meter (if there were one) is at the MAX.

Do your VU meters stay at the red-line for 100% of the time? OK, maybe on yours it would, if you have one. On mine it would go up and down a bit. Perhaps you're different?

Edited August 5, 2016 by Grangur

[4stringslow]

Ah, may have been at crossed purposes (pesky Internet forums ).

I agree with you about the input fuse.

[BigRedX]

[quote name='Alec' timestamp='1470319034' post='3105074']
If it's a kettle lead, then you'll need a 13A fuse, as most kettles are around 2,500W, and so will draw more or less the full 13A.

If, as others have observed, it's an IEC lead (as it will be for supplying kit), then all of the previous posts make it clear that IEC connectors have a 10A rating, but may be fused at 13A. And, in practice, that makes the most sense for a generic set of IEC leads. After all, they will be swapped between different bits of kit, which puts lower fuse ratings at much more risk of being blown.
[/quote]

/Thread.

There you go. That's the definitive answer. If you want to go and do something else based on previous experience that's fair enough, but the above is the correct information.

[naxos10]

[color=#282828][font=helvetica, arial, sans-serif]Grangur:[/font][/color]
[color=#282828][font=helvetica, arial, sans-serif]"Ahhh, but what you're missing is that there must be discrimination between the fuse in the lead and the fuse in the amp. That is to say that if there is a fault in the amp, the 3amp fuse inside the amp must blow before the one in the lead (designed to protect the lead) even gets excited enough to even think about blowing. (There's a technical term for this, but i can't remember and I can't be arsed)"[/font][/color]

[color=#282828][font=helvetica, arial, sans-serif]Would that term you were thinking of be Backup and Discrimination?[/font][/color]

[Musashimonkey]

Wow, this got technical quickly! I was expecting a debate on wether it's actually called a 'kettle' lead to ensue!

[4stringslow]

The whole kettle / IEC thing is another example of modern language evolving and word definitions changing through popular usage.

I'm pretty sure everyone here know that the mains leads we all use for our gear are not actually 'kettle leads', even if we don't know they are correctly an IEC lead, and even more correctly an IEC C13 lead and even more correctly a UK plug to IEC C13 lead (other countries are available).

I'm also pretty sure that anyone at a gig asking for a kettle lead would be understood perfectly well

Funny thing language.

[Alec]

[quote name='Musashimonkey' timestamp='1470399572' post='3105744']
Wow, this got technical quickly! I was expecting a debate on wether it's actually called a 'kettle' lead to ensue!
[/quote]
The problem is, while you can use an IEC C15 kettle lead in an IEC C14 inlet for any typical audio gear, you can't use and IEC C13 (typical audio/PC lead) to power a kettle via its IEC C16 inlet, owing to the ridge in the IEC C16 inlet which allows only IEC C15 connectors to mate. This restriction is all down to the IEC C15/C16 combination being rated for hot conditions, i.e., boiling water. This [url="https://en.wikipedia.org/wiki/IEC_60320"]Wikipedia article[/url] does a reasonable job of describing the connectors.

IEC C13/C14 -

IEC C15/C16 - (kettle lead)

I guess so few of us use kettles with plug/socket connectors that we've forgotten the subtle differences...

Edited August 5, 2016 by Alec