13amp Fuse Blows On Initial Start Up

[Robert]

I have a new AL-KO 3Kw Log Splitter supplied with a standard 13amp plug. When I plug it into my ring main the 13amp Fuse
blows. If I then immediately replace the fuse, I can switch it on and off with out any problem during the period I am using it. The next time that I "start up" after leaving it a day, the same thing happens and I have to go through the fuse replacement sequence again. I understand that a 3Kw motor is quite hefty. I have contacted the manufacturer, they say once the machine has been "run in" the problem should stop - but this has not happened yet. I use the cable supplied with the machine and do not use any extension cable. Has any one got any suggestions to remedy this problem please?

[big-all]

start up currents can be very high
i wonder if replacing the fuse with a 15amp would cure the problem assuming it didnt constitute a danger to the wiring!!!!!

[unclek]

See if you can get some time lag 13A fuses. They normally have a "T" on them. These will allow the motor to draw a larger current when starting and not blow.

[stevelusky]

My friend had a sliding mitre saw which had the same problem, although it was tripping the breaker in the fuseboard everytime he started it, then it would run fine after it was reset. I suggested that he used a r.c.d. thinking that it would be easier to reset this at the plug rather than have to walk to the fuseboard everytime, but since he started using it it has not tripped out at all. Dunno if ithas some sort of cusioning effect ? I did some insulation tests on the saw and its safe enough, maybe try the same thing, they only cost 5-10 quid and tbh you should be using one anyway.

[Robert]

Thank You stevelusky, that is the answer. I used my R.C.D. plug in the socket and now my Wood Splitters on/off switches work all the time without blowing the fuse!

Super,

[Wood Magnet]

Nice one Robert, and a good call Steve.

[stevelusky]

Glad it worked, I dont know why it should, Would be interested to know why though, If it blows a fuse in the plug it should have tripped the R.C.D. i would of thought ???

[leckylecturer]

Here is the technical answer

RCDs respond to a difference in current between the live and neutral.
Circuit breakers and fuses respond to a high current and will fail if their operating value is exceeded. SO, an RCD will not trip due to a high inrush current. And a fuse will not respond to an earth fault of 30mA, but an RCD will. Two different devices for two kinds of protection. The RCD would operate if your log splitter had a fault to earth.

When a motor starts, it can pull up to eight times its normal operating current.

As to why fitting an RCD will make a difference?
The circuit of an RCD has a pair of coils wrapped around a magnetisable core. This detects an imblalance and trips the circuit. Now, we use coils (inductors) in electronics to dampen changes in current. For example, surge protectors for PCs. Perhaps (and dont quote me on this, i will have to experiment), the coil in the rcd dampens the in-rush current when the motor starts.

Inductors work a bit like a capacitor. I am sure you know that a capacitor will charge and discharge much like a battery and will hold energy as voltage. A coil (or inductor) will hold energy as current! It will also charge and discharge like a capacitor and so will absorb and release energy into a circuit as the current changes.

OK, science lesson over. Hope this doesnt raise more questions.

And finally, just to be rude, if you need an electric log splitter, i suggest you get some roughage!

[stevelusky]

^^ good answer, sort of thought it was because of coils in the RCD, just nice to know why !
log splitter line made me chuckle

[Wood Magnet]

Whoo Hoo! Another Mackem with toilet humour.

[leckylecturer]

For the record, I just live in Sunderland. I was born and bred on Tyneside. Waht do you mak of that!

[Wood Magnet]

*Infiltrator Alert*