Kettle Leads

[Dawoogsta]

Does the fuse rating matter on these?? If so, what should it be?

[Monckyman]

Depends on the kettle.

[flyfisher]

. . . and if it has a fuse at all.


OK, I jest, because I'm guessing the OP is asking about a UK mains lead, but it's a serious point really because such mains leads are also available with non-fused European mains plugs, for when the amp (or whatever) is sold in Europe.

And because the manufacturer must allow for an unfused mains lead, they will have fitted some form of internal over-current protection to their equipment. This is usually just an internal fuse, though not always.

So basically, a UK mains lead can be fitted with any fuse, providing it will supply enough current to the connected device. In practice, most people will fit a 13A fuse - after all, the UK uses mains plugs rated for 13A and because no-one knows what the mains lead might be connected to, the cable itself will be rated to carry 13A.

The fact that the amp (or whatever) is highly likely to draw less current than 13A doesn't really matter because of it's own internal over-current protection. In other words, it's a 13 amp mains lead so fit a 13 amp fuse.

I know this is a long-winded answer, but I'm hoping it will help people to understand what's actually going on rather than just say '13A'.

[apa]

If there is an internal fuse in your amp the fuse in the plug is purely to protect the plug and the kettle lead. Like flyfisher says above.

A

Edited December 2, 2012 by apa

[BILL POSTERS]

Only seems like about a month ago that this topic was covered. And it went on and on and on iirc.

Me, I fit a 3A or a 5A, whatever is to hand. In Europe, where there are no fuses in the plugs, the mains trip is much smaller than the 30A or so fuse or trip used with a UK ring main. So in the unlikely event that the plug gets pulled off, or the cable gets damaged and shorts to earth,the mains fuse/trip in the consumer unit will blow just that bit more readily.

Unless your using old lighting, few pieces of kit that bands use will draw anything like 3A.

[yorks5stringer]

It's probably been covered in the other thread... but how would a mains lead for Europe w/o a fuse fit a UK socket? Don't those adaptors have a fuse in them anyway?

[flyfisher]

it wouldn't, but that wasn't my point - which was that equipment with IEC mains connectors is designed to be used with mains leads that might not be fused. Yes, UK plugs have fuses but European (and USA) ones don't. In other words, the equipment in question does not reply on a fuse in the mains lead for safe operation.

Bill_Posters is right that few pieces of band equipment will draw 3A (though some PA amps might), so 3A fuse will probably be OK, but it just isn't that important. if it was, do you really think that UK electrical regulations would allow Joe Public to choose their own fuses?

[xgsjx]

1/4" bolt FTW!

[Phil Starr]

Personally I wouldn't skip using the right fuse, they are so cheap apart from anything else that you can afford to have boixes of the things.

If the fuse in the plug blows first then it can save you the problem of finding an internal blown fuse or replacing a much harder to source fuse on the back of your gear. You are not always so lucky but it can help. If two fuses blow in succession you have a genuine problem which needs sorting.

Gear without the right fuse is less safe, Given the amount of gear from the seventies still about and the mods that people carry out over the years you have no guarantee that a lot of gear is wired to modern standards and is safe without a fuse. Think of it as a strand in a rope. The rope might hold with a strand or two broken but you wouldn't trust your weight to it if you knew a strand was cut.

Use the smallest fuse possible, as a rule use 1A for every 200W of power, so for anything below 500W use a 3A fuse and a 5A fuse for 1000W with 13A for anything over 1000W . Other values can be harder to track down at DIY/hardware shops.

[JTUK]

Used a mains lead that iuse for most of my amp stuff with a new amp and it promptly blew the fuse.
Put 13A in and all well. The power up is known to be huge on this amp..and this has fixed it.

[flyfisher]

[quote name='JTUK' timestamp='1354533243' post='1886964']
Used a mains lead that iuse for most of my amp stuff with a new amp and it promptly blew the fuse.
Put 13A in and all well. The power up is known to be huge on this amp..and this has fixed it.
[/quote]

Depends on the type of amp but, yes, they can have very large surge currents when switched on as big capacitors charge etc.

In such cases, the internal fuses will almost certainly be "slow-blow" types. Again, the amp designer will have built-in the appropriate safety protection devices so that there is no reliance on an external mains lead over which the manufacturer has no control.

[flyfisher]

[quote name='Phil Starr' timestamp='1354533014' post='1886962']
Personally I wouldn't skip using the right fuse, . . . .
[/quote]

Nor would I, but the 'right fuse' will already be present inside the amp because the manufacturer cannot rely on what lay-people put in an external mains lead and, as already discussed, it's quite legitimate for a non-fused mains lead to be used in some countries, so clearly a fuse in the mains lead is not an all-important safety consideration.

On that basis, it's quite legitimate for a 13 amp mains lead to be fitted with a 13A fuse, whatever the type of equipment it's plugged into (appliances with a fixed mains cable are a different case).

[quote name='Phil Starr' timestamp='1354533014' post='1886962']
If the fuse in the plug blows first then it can save you the problem of finding an internal blown fuse or replacing a much harder to source fuse on the back of your gear.
[/quote]
Equipment fuses are only slightly harder to source. They are usually standard 20mm fuses and are widely available from pretty much any electrical shop. If the equipment fuse(s) are externally accessible then it's well worth carrying spares in the gig bag.

[quote name='Phil Starr' timestamp='1354533014' post='1886962']
Gear without the right fuse is less safe, Given the amount of gear from the seventies still about and the mods that people carry out over the years you have no guarantee that a lot of gear is wired to modern standards and is safe without a fuse.
[/quote]

Yes, but how many people get secondhand gear fully checked by a qualified person before using it? Even PAT testing is mostly about earth leakage type testing and certainly won't tell you if the internal fuse has been replaced with a bolt or if the circuitry has been modified.

But, again, a fuse in the mains plug doesn't magically make things much safer - or are you suggesting that all our European and American members are at greater risk than UK members?



[quote name='Phil Starr' timestamp='1354533014' post='1886962']
Use the smallest fuse possible, as a rule use 1A for every 200W of power, so for anything below 500W use a 3A fuse and a 5A fuse for 1000W with 13A for anything over 1000W .
[/quote]

Yes, that will do no harm. However, I'd advise carrying a lot of spare fuses unless you can be sure to always match the "correctly" fused mains leads in the same equipment everytime you put all your band gear together.

My experience is that mains leads have a habit of finding their way into a big box and people just grab them as needed while putting everything together. This is fine if all the (13amp) leads are (correctly) fitted with 13A fuses but if you have a mixture of 3A, 5A and 13A fused leads then it'll be quite common for the 'wrong' lead to be fitted to the 'wrong' piece of gear and fuses will inevitably blow.

What's more, they may not blow immediately because of the way fuses work. Thus, for example, a PA amp with 5A fused mains lead may work fine during a short sound check (depending on its power of course), but if the full-on power consumption is slightly over the mains plug fuse rating then the fuse could blow some minutes into the first set.

[Dawoogsta]

Thanks people...all of your input is much appreciated!! :-)

[Phil Starr]

Hey I don't want to get into a big one on this, or get all preachy, I'm as big an idiot as the next person when it comes to my own health and safety but these are public forums and the advice we give is read by hundreds of people so when safety is involved we should be at least factually accurate. I'd hate to think of a fellow BC'er coming to harm through poor advice. Sod it, I'm preaching

[quote name='flyfisher' timestamp='1354536188' post='1887005']
Nor would I, but the 'right fuse' will already be present inside the amp because the manufacturer cannot rely on what lay-people put in an external mains lead and, as already discussed, it's quite legitimate for a non-fused mains lead to be used in some countries, so clearly a fuse in the mains lead is not an all-important safety consideration.

On that basis, it's quite legitimate for a 13 amp mains lead to be fitted with a 13A fuse, whatever the type of equipment it's plugged into (appliances with a fixed mains cable are a different case).

[b]You can't assume the person before you put the right fuse in, the European sockets you refer to are all fused by law but the fuse for each separate circuit is back in the fuse box, they don't use ring mains.[/b]




Yes, but how many people get secondhand gear fully checked by a qualified person before using it? Even PAT testing is mostly about earth leakage type testing and certainly won't tell you if the internal fuse has been replaced with a bolt or if the circuitry has been modified.

But, again, a fuse in the mains plug doesn't magically make things much safer - or are you suggesting that all our European and American members are at greater risk than UK members?

[b]Well their mains is 115 volts lower than ours and all the sockets are fused anyway, if the socket is fused you don't need the plug to be fused as well.[/b]



My experience is that mains leads have a habit of finding their way into a big box and people just grab them as needed while putting everything together. This is fine if all the (13amp) leads are (correctly) fitted with 13A fuses but if you have a mixture of 3A, 5A and 13A fused leads then it'll be quite common for the 'wrong' lead to be fitted to the 'wrong' piece of gear and fuses will inevitably blow. What's more, they may not blow immediately because of the way fuses work. Thus, for example, a PA amp with 5A fused mains lead may work fine during a short sound check (depending on its power of course), but if the full-on power consumption is slightly over the mains plug fuse rating then the fuse could blow some minutes into the first set.
[/quote]

You're right about mixing leads up but very little of our gear uses more than 5 amps even a 1000W PA amp only runs at a fraction of its power (technically if you are running flat out with a 20dB dynamic range then you'll only be pushing 50W a side at about 85% efficiency or 120W, roughly 0.5A so you won't be blowing fuses unless something is wrong)

So I know I could bore for England on this but I worked as an electrician for years and in electronics for longer and you don't tell people to use the wrong fuses and expect that there will be no consequences, sooner or later even though the risk is low someone who takes your advice will get hurt. Most accidents happen because of a chain of minor events lead to a catastrophic finale not because of a single large error. Using the right fuse won't protect everyone all of the time and adding one link in the safety chain won't save everyone from electric shock forever but using the right fuse is boringly sensible and telling people not to bother actually opens you up to the distant possibility of criminal liability, should someone take your advice and get hurt. Why would you want someone to take a risk however small.

[stingrayPete1977]

Here you go then clever clogs

The fuses at the distribution board for the radial circuits in the EU will be a minimum of 16A possibly 20A so what difference will a 13A fuse here make?
If it was covered by an BS60898 MCB or even an BS61009 RCBO even of 32A there is a good chance it will blow before a 13A BS1362 fuse anyway especially if the trip is a B type or type 2 BS3871 MCB.

If it was so dangerous the lead would not be removable as has been said before, the fuse covers the piece of cable which is usually no less than 1.5mm flex rated at approx 18A (or 1.0mm HR/similar rated higher than single core 1.0mm) hence the max 13A fuse which is the biggest available for a plugtop.

FWIW all three of the leads that came supplied with my Genz Benz amps state 13A on the fuse carrier/plug molding and have 13A fuses installed from the supplier so I think I would have more chance of sueing them that a member of BC if it were the case

Edited December 4, 2012 by stingrayPete1977

[flyfisher]

[quote name='Phil Starr' timestamp='1354615091' post='1887972']
. . . . but these are public forums and the advice we give is read by hundreds of people so when safety is involved we should be at least factually accurate.. . . and you don't tell people to use the wrong fuses and expect that there will be no consequences, . . .
[/quote]

Can you point out where I have been 'factually inaccurate'?

The correct fuse for a 13A IEC mains lead is 13A.

StingrayPete has described the details very well above.

[Marvin]

I always try to use the lead that was provided with the amp or combo and only that lead, and use the same rated fuse as supplied by the manufacturer. Not very technical I know but there you go.

[flyfisher]

A perfectly sound approach. In fact, equipment manufacturers can expect nothing more from customers because they cannot rely on people understanding ohm's law or how to choose the 'correct' fuse rating?


I've just been checking my Ashdown amp manual and it says nothing about the fuse in the mains lead. What it does say is that the rating for the fuse in the mains input socket on the amp itself is marked on the amp and should always be replaced with an identical fuse.

So, we have a wall outlet protected by a 30/32A device in the consumer unit, which provides the correct protection for the ring main wiring. We then have a 13A mains lead plugged into that wall outlet, which is correctly protected by a 13A fuse in the mains plug. We then have an amplifier (in this case) connected to the 13A mains lead, which is protected by the appropriate fuse on the amp itself.

Correct ratings for all these fuses/devices are clearly marked on the devices themselves. 30/32A in the consumer unit, 13A on the mains plug and ??A on the amplifier (or other device plugged in).

In most cases, it will do no harm to use a lower rated fuse in the mains plug if the device doesn't require much power, but not doing so doesn't make things any less safe. Might as well argue that it would be safer to replace a 30A ring-main fuse in a consumer unit with a 15A fuse because hardly anyone is going to be drawing over 7kW from a typical domestic ring-main these days - but that would miss the point.

[stingrayPete1977]

[quote name='flyfisher' timestamp='1354619744' post='1888084']

So, we have a wall outlet protected by a 30/32A device in the consumer unit, which provides the correct protection for the ring main wiring. We then have a 13A mains lead plugged into that wall outlet, which is correctly protected by a 13A fuse in the mains plug. We then have an amplifier (in this case) connected to the 13A mains lead, which is protected by the appropriate fuse on the amp itself.


[/quote]

This is essentially what the Regs book states throughout, if it were an exam you would get an A*
A fuse and means of isolation at any point where the circuit either divides or reduces in conductor size is the basic jist of it.

[tauzero]

[quote name='Phil Starr' timestamp='1354615091' post='1887972']
[quote name='flyfisher']
But, again, a fuse in the mains plug doesn't magically make things much safer - or are you suggesting that all our European and American members are at greater risk than UK members?
[/quote]
Well their mains is 115 volts lower than ours and all the sockets are fused anyway, if the socket is fused you don't need the plug to be fused as well.
[/quote]

USA mains is 120V but European mains is 230V. Just a minor point...

[BILL POSTERS]

[quote name='tauzero' timestamp='1354625479' post='1888245']
USA mains is 120V but European mains is 230V. Just a minor point...
[/quote]



Just being pedantic, and I could be wrong, I'm sure there are those on here who will know better. But I believe USA mains is 220V, but put simply, its split in the middle, ie 110. 0. 110. Sockets and portable appliances work as 110v, but larger fixed, high current things, like cookers and water heaters are connected across the two and are 220V. Otherwise you'd need cables an inch thick to feed the average house.

btw, the plug fuse isnt there to protect the equipment, its there to protect both the cable, and you from the consequences of it getting damaged and/or overheating.

[Marvin]

Kettle leads should only ever be attached to kettles, end of. Now someone make the tea.

[flyfisher]

[quote name='BILL POSTERS' timestamp='1354654703' post='1888870']
Just being pedantic, and I could be wrong, I'm sure there are those on here who will know better. But I believe USA mains is 220V, but put simply, its split in the middle, ie 110. 0. 110. Sockets and portable appliances work as 110v, but larger fixed, high current things, like cookers and water heaters are connected across the two and are 220V. Otherwise you'd need cables an inch thick to feed the average house.
[/quote]

Pretty much this, though the precise numbers are nominal because there's a pretty wide tolerance on the mains supply (in all countries).

For example, UK mains used to be 240V and mainland Europe was 220V. Then the EU harmonised everything to 230V.

But in practice, nothing was actually changed except the stated tolerances within each country. So the UK's 240V mains became 230V -6% to +10% and Europe's 220V became 230V -10% to +6%, meaning that what came out of the wall sockets was still the original 220V or 240V but it was now within the newly harmonised 230V tolerances.

A marvellous bit of bureacracy that changed nothing. Equipment manufacturers didn't care either because they had long been designing their stuff to work off anything from 220V to 240 V anyway - indeed, modern PSUs generally work from around 90V to 260V, which makes life much easier for manufacturers selling stuff globally.

Actually, it's not quite true that nothing has changed because electrical transmission is gradually changing to be actually 230V as they upgrade or replace the network transformers and thus change them from 220 or 240 to 230V, but none of it makes any practical difference as far as what we plug into our wall sockets, it's all invisible housekeeping really.



[quote name='BILL POSTERS' timestamp='1354654703' post='1888870']
btw, the plug fuse isnt there to protect the equipment, its there to protect both the cable, and you from the consequences of it getting damaged and/or overheating.
[/quote]

That's a bit more contentious, I'd say. A fuse will offer no practical protection against a damaged cable exposing someone to bare wires and thus a serious shock hazard.

The resistance of the human body varies a lot depending on skin condition etc and the current that would flow during an electric shock situation will also vary a lot depending on the nature of contact with the wires, but suffice to say that even a 1 amp fuse would be highly unlikely to blow if you were the only thing connected across the mains and even if it did it would probably be too late because, unfortunately, it can take far, far less than this to cause death.

I would never rely on a fuse as a form of electric shock protection.

[BILL POSTERS]

[quote name='flyfisher' timestamp='1354666981' post='1889049']
a 1 amp fuse would be highly unlikely to blow if you were the only thing connected across the mains and even if it did it would probably be too late because, unfortunately, it can take far, far less than this to cause death.

I would never rely on a fuse as a form of electric shock protection.
[/quote]

The clue to what Imeant is in what I wrote.

[b][i]Getting damaged and /or overheating.[/i][/b]

13A fuse, thin cheapo kettle lead etc, partial short or damageed cable, -= heat = fire.. Beer spilled into an amp between the mains coming in and the fuse, tinsel for eaxmple,used to be common in the back of TVs when I was in the TV trade in another life, try putting that across the mains and see it burn before a 13A fuse blows. The possibilites are endless. Smaller the fuse, the safer.

Before anybody bothers to tell me, I know Modern tinsel doesnt conduct, Thats because the stuff that used to was a fire hazard, and a shock hazard with old fashined mais driven christmas tree lights. twas just an example/

Edited December 5, 2012 by BILL POSTERS

[bremen]

[quote name='BILL POSTERS' timestamp='1354654703' post='1888870']
. But I believe USA mains is 220V, but put simply, its split in the middle, ie 110. 0. 110. Sockets and portable appliances work as 110v, but larger fixed, high current things, like cookers and water heaters are connected across the two and are 220V. Otherwise you'd need cables an inch thick to feed the average house.


[/quote]

I'd always wondered how they got 3kW out of 110V, cheers for that!