Fuse ratings?

Discussion in 'Amps and Cabs [BG]' started by nil, Nov 27, 2001.

  1. I'm a little confused about fuse ratings and 110v / 240v power...

    If my WT800 comes standard from the factory with a 250v/10A slow-blow fuse (10A, according to the manual, is correct for USA use), is this the same rated fuse I should use if I run the amp on a 240v AC supply?

    ie Do you use the same rated (in amps) fuse for both 110v and 240v equipment?

    Thanks! :)
  2. Power = Volts x Amps, so if you double the voltage (120 -> 240), you halve the current (10 -> 5) to keep power the same. There should be a voltage selector switch if your amp can do this without rewiring the power transformer. The correct fuse value depends on the AC supply voltage.

    That's the textbook answer.

    That 250V rating on your 10A fuse refers to the fact that it is rated OK for up to 250VAC.

    Consult the manual for what's right for your amp.

  3. I'm with Throb.

    Make sure you fit the same type of fuse. AC power circuits usually require Anti-surge types because of the switch on surge of current caused by the inductance of the mains transformer. Toroids are worse for this than EI wound transformers. (Of course, you'll probably not know what type of transformer is fitted to your amp.)

    Although the rules / laws governing fuse usage will naturally vary from country to country and perhaps, even, from state to state, we would go for ceramic bodied types, sand filled in the UK: ordinary glass bodied fused are not suitable for mains use, here, even though they would have the same electrical characteristics.

    Equipment fuses are generally 20mm length these days (as opposed to 1 1/4" fuses from the past): a straight 5Amps is perhaps less common than 6.3Amps. I would fit the latter in this situation.

    Again, I agree with Throbbinut: check the user manual.

  4. Thanks guys, but the problem here is that the user manual doesn't specify the AMP rating for 240v use.

    With the WT800 you simply flip the fuse holder over to swap voltages (I haven't delved into how it engages the taps on the transformer). The fuse is the same physical size for either voltage.

    In short, if the recommended AMP rating for US use (110v) is 10A, should I be running a 240v/5A slow-blow for 240v use, or stick with the 10A?
  5. MikeyD


    Sep 9, 2000
    It probably depends a lot on the design of the power supply; that line fuse has to protect the power supply first - then everything else downstream will be protected. I can't comment on it further without actually seeing a schematic of the power supply.

    However, given that the output is probably the real constraint, if a 10-amp fuse works at 120V, then the amplifier will probably work just fine with a 5-amp fuse at 240V. In both cases, it allows a feed of 1200 volt-amps. I guess I recommend getting the 5-amp fuse, but keep the 10-amp handy in case this doesn't work and you blow it.

    - Mike
  6. Cool, that kinda makes more sense...yeah, it does pull 1200W so it sounds like 5A is correct for 240V operation.

    I would've asked Eden (I think I have a couple of times) but they're always pretty sparse on any details they provide...and the manual only mentions that "10A is correct for US use". Great...

    I'm not a sparky so things like this often get the best of me! :D

  7. My gut feeling would be to go just that little bit higher and use a 6.3Amp fuse instead of the "calculation" value of 5 Amps for UK Mains voltage.

    Get an Anti-surge type - denoted by the letter "T", in a variety known as HBC. These are ceramic boddied fuses ideally suitable for UK mains applications.

  8. I've brought this thread back from the dead as im wondering a similar thing...

    My question is related directly to the Eden WT800A. To use a US 800A on 240v is it correct that I just need to flip the fuse holder over and insert a 5amp fuse? Im pretty sure that is what the previous posts are implying.. :meh:

    I too have written to Eden as the manual only states US usage requirements.