Ohm's Law

  morddwyd 12:32 06 Jun 2012

My electric hedge trimmer keeps blowing its 3 amp fuse.

I've measured the off-load resistance at 23 ohms.

Now my Ohm's Law is a bit rusty, but am I right in thinking that 240 volt across 23 ohms will require more that a 3 amp fuse?

  Quickbeam 12:41 06 Jun 2012

Ohm my God... I had a similar problem with the new garage wiring being on trip outs when rewired last month. The mower would run OK on a 5 amp fuse with wet grass, then it started tripping out.

So I just stuck a 10 amp trip in to allow for the start up loading, if that blows, then there's definitely something wrong.

  Woolwell 12:49 06 Jun 2012

I hope you have a RCD.

  john bunyan 12:56 06 Jun 2012

I am no electrician, but only use 3 amp fuses for lights. I would have thought a 10 amp would be needed, but, as Woolwell says, do use a RCD

  amonra 13:00 06 Jun 2012

The 23 ohms is a bit meaningless because it's the impedence that matters to an AC supply. As quickbeam said earlier, stick a bigger fuse in, stand back, switch on and get ready to switch off again. Very often in small machines, the manufacturer fits a radio-interference suppression capacitor across the input switch. These go wrong quite frequently and are easily snipped off to prove a point. It's a case of suck-it-and-see !

  Condom 13:01 06 Jun 2012


I was useless at that when I was at school but my B&D has a 13 amp fuse in its pre-fitted plug and although I seldom use it it has never blown either its own fuse or the RCD.

  wiz-king 13:05 06 Jun 2012

Ohm's law is not for AC use! I would try a 5A fuse or if you can still read the Wattage on the service plate then Watts/220 = Amps

  interzone55 13:09 06 Jun 2012

I always look at the Watt figure on the label, then divide by 230 to get the fuse.

If it's 1000w you'll need a 5amp

  Aitchbee 13:28 06 Jun 2012

Sometimes trying a different electrical socket in the house makes a difference...my ancient X-BOX only 'fires up' on one...out of about fifteen. (Fifteen-To-One!)

  morddwyd 14:08 06 Jun 2012

I know enough about Ohm's Law (and H&S!) to know that fitting a bigger fuse is an absolute no-no.

If the manufacturer says fit a 3 amp who am I to argue<

Didn't trip the RCD any any of the occasions it's blown.

  Aitchbee 14:20 06 Jun 2012

Buy a battery-operated hedge-trimmer...you'll get about twenty minutes trimming per charge.

This thread is now locked and can not be replied to.

Elsewhere on IDG sites

AMD Radeon Adrenalin release date, new features, compatible graphics cards

8 brilliant character artists speaking at Pictoplasma 2018

iMac Pro release date, UK price & specs

Football : comment regarder la Ligue 1 en direct ?