Using USA inbuilt fuses with UK kettle lead fuses compatibility question?

[Luke Jon Gibson]

I'm not an electrician, but I thought this would be the best place to ask this sort of thing.

I have just recently purchased some professional Audio speakers from the US, but they are built for international use with a switch for 110v and 240v usage. My problem is that the IEC/kettle power cables provided are 2 prong, which obviously doesn't fit a UK power point. The speakers themselves have a fuse built into them of 2.5amps, the instructions say not to use any other amp level for the speaker, but it doesn't mention anything about the power cable, as the US leads have no inbuilt fuse of their own.

I have 2 British kettle leads, but the fuse in them is 5amp, so my question is, will the 2.5amp fuse inside the speaker be able to cope/regulate the 5amp fuse inside the kettle lead, or should I buy 2.5amp fuses for the kettle leads first?

As I said, I'm not an electrician so I hope that makes sense.

Cheers.

Luke

 

[Strima]

To be sure stick a 3A fuse in the plug. The fuse in the speakers should protect all the electric gubbins. Can't see too many problems as the original cable is unfused, a lot of countries rely upon the fuse at the fusebox to provide their protection.

 

[Luke Jon Gibson]

Okay thank you for the reply, The reason I ask is, new gear, wanted to hear it tonight. Don't have any fuses to hand and everywhere will be closed now lol. But if it's not going to be safe to do then I will wait until tomorrow.

 

[Strima]

I understand your apprehension, shame a lot of people don't show it when plugging in their shiny new toys. If it was me I'd just plug it in and go for it. 5 amp would be more than fine TBH, it takes a lot more than that to blow them as they're designed to blow at certain times under certain loads. At a guess the fuse in the unit will be a glass enclosed one which would pretty much blow straight away if too much power is drawn. The fuse doesn't control how much power is supplied to the item, it only protects in case of fault.

 

[Richard Burns]

Since you have a fuse in the speakers this is likely to be after the voltage selector. I.e you will apply either 110V or 240V from the supply cord, the internal transformer will drop the voltage to the usable level required for the speakers and then the fuse will be in place. Depending on the voltage used in the speakers then the current could be internally higher than the current drawn by the supply cord, so difficult to tell which fuse you would need.

So the speakers will be safe no matter whether there is an external fuse or not, standard UK plug fuses are easily available in 3A and 13A although 2A and 5A are also available.
I would tend to leave the 5A in place and you will probably find in the case of a fault in the speakers that the internal fuse is fast blow and will go first making the external fuse only useful for faults in the supply cable or transformer.

 

[Strima]

Easy when someone explains it properly...

 

[Richard Burns]

Easy when someone explains it properly...

Perhaps just differently!:smiley2:

 

[Luke Jon Gibson]

I would tend to leave the 5A in place and you will probably find in the case of a fault in the speakers that the internal fuse is fast blow and will go first making the external fuse only useful for faults in the supply cable or transformer.

Ah, okay, well after the suggestion of 3amp fuses I went digging around the house and found some. So I put those in and everything seems to be working nicely, but now that I have the 3amp do you recommend I switch back to the 5amp? Or is 3amps still the better choice for future refference?

BTW, thank you again to the both of you for helping me out, I posted this question on several audio forums and no one has been forth coming with an answer so I'm am very grateful you've been able to help me out.

 

[Richard Burns]

Without knowing the power rating of the speakers it is difficult to advise on the size of fuse, but if it is working OK on a 3 amp fuse then it is likely to continue to work. A possible method of managing it would be to use the 3 amp fuse and if it blows at any time change for a 5A but this is not really good practice!
If the speakers are rated at over 700W total power consumption then I would change the fuse back to 5A, if not then 3A should be fine.

 

[Luke Jon Gibson]

M-AUDIO - Studiophile DSM3 - High-Resolution DSP Studio Monitor with Dual 6.5-Inch LF Drivers this is them if that helps? Cheers

 

[Richard Burns]

Most of the specs are way over my head although they do seem to be good speakers.
The item I noted was that the output is total 180W, now this is not a good indicator of input however if we were to say there was a 50% loss of power through the speakers (which I would have thought high) you would still only be at 360W so based on this (with the understanding that I do not know the losses that may actually occur or what items may be in the speakers as well) a 3A fuse will be fine and will not blow in normal use.

There will be no damage caused to the speakers by changing the fuse size as it is only a protective measure and the intent of the system is to have no protective measure in the power cord.

Good listening!

 

[Guitarist]

Think about it... The cable had no fuse in originally so the speakers don't need one, hence the internal fuse.

 

[netblindpaul]

I hope these are for personal use and you have no problems with them at home.