Power cable confusion - 250v fuse?

[Paolo85]

I have this hartke HD 25 with EU plug bought from Bax. I want to replace the power cable with a UK one as I assume that would be safer than using a socket adapter.

The problem is I don't know a thing about any of that. It seems the amp can take 220v-240v so in that sense, to my understanding, any UK kettle lead would do. But then there is a warning "use only with 250v fuse". If I google power cables I find no indication of fuse's voltage. Maybe I can find indications on the fuse's amperage.

Do you know how I would go around that? Do you know specialised  shops that can give advice or provide more info on their cables?

Thanks!

[BigRedX]

Two things:

 

1. the fuse in a mains lead is there to protect the lead only, not the equipment it connects to.

 

2. Any retailer supplying electrical goods to the UK market are legally obliged to supply a mains lead with a UK plug on it. Get in touch with the shop that sold it to and remind them of their legal obligation.

[atsampson]

That's an IEC C14 ("kettle lead") socket with a built-in fuse holder - you can pull the plastic bit below the socket out to replace the fuse. That's what the note on it and the specs printed below are referring to.

 

It says the amp's fuse is 315 mA (0.315 A) so any IEC lead will be fine. As BigRedX says, the fuse in the plug is only there to protect the cable - they usually come with a 13 A fuse which is much more than the amp will draw, and more than the 10 A the IEC connector is rated at.

[Paolo85]

3 minutes ago, atsampson said:

As BigRedX says, the fuse in the plug is only there to protect the cable

I see. To be honest I am more concerned about the risk of fire and similar stuff than to safeguard my 25w amp. Not sure if that remains a risk?

 

6 minutes ago, atsampson said:

- they usually come with a 13 A fuse which is much more than the amp will draw, and more than the 10 A the IEC connector is rated at.

 

Unfortunately I am quite ignorant about all that. Does that mean "more than you need, you are good", or "too much, you should replace the fuse"

Thanks!

[DGBass]

1 hour ago, Paolo85 said:

to my understanding, any UK kettle lead would do.

Yes thats about what you need to plug in safely to a UK supply outlet. As was mentioned, a retailer should supply you with one. I know retailers like Thomann for example automatically pick and send a UK cable for orders bound for GB. If you prefer getting one yourself they can be purchased just about anywhere these days online.  I just recently renewed a few of my leads, this might give you an idea what to search for. Cable length is a persoanl choice, 3 metres works for me!

 

The fuse tab on your amp in your photo will contain an equipment fuse, usually a small 250V 20mm glass type like below. Yours is rated T(means slo blo) 0.315A. You don't need to worry about it if its a new amp. These only usually blow if the amp develops an internal fault which is in my experience rare within a warranty period. 315mA is also unlikely to generate a raging firestorm if things go bad, so I also wouldn't worry about the internal fusing as its a normal safety feature of your new amp.

 

 

[Downunderwonder]

Everywhere else in the world fuses the house wiring so plug fuses are not required.

 

Your amp will fine with anything that can plug into it that is rated to supply its needs. 60w is not a lot.

 

Current blows fuses not voltage. Since the amp is destined for 220 to 240 v supply it should have the correct fuse already in it.

 

 

[BigRedX]

9 hours ago, DGBass said:

As was mentioned, a retailer should supply you with one.

 

There's no should about it. UK law states that if you are supplying electrical equipment to the UK it MUST come with a lead fitted with a UK mains plug, or at the very least an adaptor that fits completely over the non-UK plug with no possibility of the user being able to touch the contacts of the wrong plug. Any retailer that is not prepared to fulfil these legal obligations should be be selling electrical equipment to the UK. If I was the OP I'd be reminding Bas of their legal obligations, if necessary by social media so that the rest of the world can see how poor they are.

[Downunderwonder]

Big little typo there Red.

[BigRedX]

1 hour ago, Downunderwonder said:

Big little typo there Red.

 

I'm sure there's loads but I'm dyslexic so I'll never see it unless someone points it out.

[Downunderwonder]

9 hours ago, BigRedX said:

 

I'm sure there's loads but I'm dyslexic so I'll never see it unless someone points it out.

 

Only one that I saw.

 

12 hours ago, BigRedX said:

Any retailer that is not prepared to fulfil these legal obligations should be be selling electrical..

 

Try using shorter sentences. That makes it harder to mix things up.

 

Using more paragraphs also helps.

[Bill Fitzmaurice]

15 hours ago, Downunderwonder said:

Everywhere else in the world fuses the house wiring

GB doesn't?

[Downunderwonder]

55 minutes ago, Bill Fitzmaurice said:

GB doesn't?

Dunno. I expect they do these days but must be enough dodgy 19th century wiring around still that they persist in fusing the plugs on IEC leads? Why else?

[Bill Fitzmaurice]

The only logical explanation for why else is to provide a secondary level of protection. Assume that the mains outlet uses wire with a 20 amp capacity, connected to a 20 amp breaker at the service entrance. Now assume the wire from the outlet to the device is only 10 amp capable, but it's connected to a 20 amp device. That wire could overheat and short out or cause a fire long before the 20 amp breaker tripped. Happens all the time. Separately fusing the lead at its capacity removes that hazard.

[Downunderwonder]

In NZ the max on any device with a standard 3 pin plug is 10A I think. High current stuff needs its own outlet with a different plug.

[BillyBass]

@Bill Fitzmaurice & @Downunderwonder Electrician here.  In the UK, every circuit would be protected by a device ensuring automatic disconnection of supply, at the fuseboard.  This will be either a fuse, a miniature circuit breaker, an RCBO or an AFDD.  The reason we have fuses in plugs is due to a quirk of history.

 

The Germans bombed the crapp out of us in world war 2 and after it finished a lot of rebuilding was done.  Electricity for the masses was a relatively new thing anyway, here in north London, we didn't get a power station until the 1920s and initially, I assume, it would have been the more affluent and the middle classes that got an electricity supply.

 

The usual 20A circuit Bill mentions was, back then a 15A fused 'radial' circuit, using 2.5mm csa copper cable (actually the imperial equivalent of about 2.5mm).  Radial circuits are: fuse>socket>socket>socket etc, the 'radial' or round name comes from the cable having the line or live conductor going out to each socket and then a neutral coming back, but both conductors, along with an earthing conductor, are enclosed in the same cable.

 

To save money after the war the 'ring final circuit' was invented (fuse>socket>socket>socket>fuse).  This used the same sized cable but then looped back into the fusebox, so there are two cables coming from the fuse, the combined surface area would be about 5mm, which was enough to take 30amps.  It became a cheap way of doubling or tripling the capacity for very little extra copper.

 

The trouble with ring final circuits is that there are some inherent safety issues.  One such issue, the fact that there could be, potentially 30 amps (or 32amps with modern circuits) passing through sockets connected to leads and appliances that would be fried by 30/32 amps (single sockets in the UK are rated at 13A.  Double sockets are also rated at 13A but, anecdotally, can take up to 18-19A before they are put under serious strain).  

 

Consequently, plugs are fused.  Standard domestic plugs have a 13A fuse at most, though, 3A, 5A, 7A and 10A are common fuses that might also get used.  As @BigRedX correctly points out above, the fuse is there to protect the cable, so if a kettle lead can only take 10A, it should have a 10A fuse at most, not 13A.

 

Only three countries in the world have 'Ring final Circuits'.  The UK, Ireland and one country in the Middle East.  They save money at the expense of safety.

Edited June 3, 2023 by BillyBass

[Downunderwonder]

I guess that makes sense and reminds me why I never became an electrician.

[Bill Fitzmaurice]

The ring circuit notwithstanding it's as I surmised, the available current at the outlet may be much higher than the lead being plugged into it can handle, so the lead is fused. The US isn't all that different. Most circuits have a 20 amp capacity, while the lead going to, say, a lamp is only 15 amp rated. But that much differential isn't enough to justify separate fusing of the lead. In theory very low current devices could use a smaller gauge lead, say 5 amp or less capable, but we don't see that. Even with a table lamp the smallest gauge lead tends to be 1mm.

[Chienmortbb]

On 02/06/2023 at 21:54, Bill Fitzmaurice said:

GB doesn't?

Of course, we do or, more correctly, we fit circuit breakers to each ring circuit. For a normal wall socket ring main circuit, it is 32A.

 

All plugs (plug top to our sparks friends) have fuses rated at 250V AC and a current that will protect the lead/cable/cable cord. It will be as low as possible. Never try to out guess the manufacturer. They rate onboard fuses at a rating that will allow for normal operation of the unit.

[agedhorse]

On 03/06/2023 at 00:36, BillyBass said:

@Bill Fitzmaurice & @Downunderwonder Electrician here.  In the UK, every circuit would be protected by a device ensuring automatic disconnection of supply, at the fuseboard.  This will be either a fuse, a miniature circuit breaker, an RCBO or an AFDD.  The reason we have fuses in plugs is due to a quirk of history.

 

The Germans bombed the crapp out of us in world war 2 and after it finished a lot of rebuilding was done.  Electricity for the masses was a relatively new thing anyway, here in north London, we didn't get a power station until the 1920s and initially, I assume, it would have been the more affluent and the middle classes that got an electricity supply.

 

The usual 20A circuit Bill mentions was, back then a 15A fused 'radial' circuit, using 2.5mm csa copper cable (actually the imperial equivalent of about 2.5mm).  Radial circuits are: fuse>socket>socket>socket etc, the 'radial' or round name comes from the cable having the line or live conductor going out to each socket and then a neutral coming back, but both conductors, along with an earthing conductor, are enclosed in the same cable.

 

To save money after the war the 'ring final circuit' was invented (fuse>socket>socket>socket>fuse).  This used the same sized cable but then looped back into the fusebox, so there are two cables coming from the fuse, the combined surface area would be about 5mm, which was enough to take 30amps.  It became a cheap way of doubling or tripling the capacity for very little extra copper.

 

The trouble with ring final circuits is that there are some inherent safety issues.  One such issue, the fact that there could be, potentially 30 amps (or 32amps with modern circuits) passing through sockets connected to leads and appliances that would be fried by 30/32 amps (single sockets in the UK are rated at 13A.  Double sockets are also rated at 13A but, anecdotally, can take up to 18-19A before they are put under serious strain).  

 

Consequently, plugs are fused.  Standard domestic plugs have a 13A fuse at most, though, 3A, 5A, 7A and 10A are common fuses that might also get used.  As @BigRedX correctly points out above, the fuse is there to protect the cable, so if a kettle lead can only take 10A, it should have a 10A fuse at most, not 13A.

 

Only three countries in the world have 'Ring final Circuits'.  The UK, Ireland and one country in the Middle East.  They save money at the expense of safety.

Well stated. 

[Chienmortbb]

On 03/06/2023 at 08:36, BillyBass said:

One such issue, the fact that there could be, potentially 30 amps (or 32amps with modern circuits) passing through sockets connected to leads and appliances that would be fried by 30/32 amps (single sockets in the UK are rated at 13A.  Double sockets are also rated at 13A but, anecdotally, can take up to 18-19A before they are put under serious strain).  

I should have read your post before posting myself. However it is only the cable and connection  point that passes  the current. The socket will only pass what is being drawn by appliances attached to it.

 

One other word of caution. Many Far Eastern imports come with IEC C14 (kettle) connectors but are fitted with 5A cable. That’s barely enough for an 800W amp.

 

 

[BillyBass]

27 minutes ago, Chienmortbb said:

I should have read your post before posting myself. However it is only the cable and connection  point that passes  the current. The socket will only pass what is being drawn by appliances attached to it.

That is why we fuse the plugs and not the sockets.  Something I commonly see in kitchens in London is a double socket used for an electric kettle (roughly 11 amps) and a toaster (up to about 7 amps).  Putting the kettle on while you are making toast is really putting that socket under strain, though the fuses in the plugs and the device in the fuseboard would not see that.  And don't get me started on extension leads!  

39 minutes ago, Chienmortbb said:

One other word of caution. Many Far Eastern imports come with IEC C14 (kettle) connectors but are fitted with 5A cable. That’s barely enough for an 800W amp.

Far Eastern imported electrical appliances should be used with caution, or not at all!  I have seen fake CE marks on Chinese/Far Eastern appliances.  I would trust Japanese stuff though.

 

[Chienmortbb]

2 hours ago, BillyBass said:

That is why we fuse the plugs and not the sockets.  Something I commonly see in kitchens in London is a double socket used for an electric kettle (roughly 11 amps) and a toaster (up to about 7 amps).  Putting the kettle on while you are making toast is really putting that socket under strain, though the fuses in the plugs and the device in the fuseboard would not see that.  And don't get me started on extension leads!  

Yup, Washing mashing plus Tumble Dryer on a Double Socket? On high heat and a cotton wash, that is crazy.

2 hours ago, BillyBass said:

Far Eastern imported electrical appliances should be used with caution, or not at all!  I have seen fake CE marks on Chinese/Far Eastern appliances.  I would trust Japanese stuff though.

I had a lead with a charger that was moulded, and the plug top had no fuse.

 

 

 

Edited June 5, 2023 by Chienmortbb

[agedhorse]

6 hours ago, Chienmortbb said:

I should have read your post before posting myself. However it is only the cable and connection  point that passes  the current. The socket will only pass what is being drawn by appliances attached to it.

 

One other word of caution. Many Far Eastern imports come with IEC C14 (kettle) connectors but are fitted with 5A cable. That’s barely enough for an 800W amp.

 

 

Hold on a minute, 5A is plenty more than enough for an 800 watt amp (especially if it's SMPS/class D). 

 

If you were to do then math, with an 80% efficient amp (typical for a quality SMPS/class D), the IEC safety regulations calculate the input power as: (rated audio power x 1.2) x 0.125 duty cycle, so for an 800 watt amp this would be 120 watts mains input. Now if you wanted to use a higher duty cycle than the minimum (I typically use between 33% and 40% myself) to account for overdriving the power amp or high levels of compression, the calculation would be (800W x 1.2) x 0.40 = 384 watts input. Now divide by 230V and you get 1.67 amps which is EASILY handled by a 5A cordset (with the correct fuse for protecting the cord).