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So in a moment of clumsiness I caught the hedge trimmer’s cable with the blade. Cut clean through with a spark.
What surprised me was the fuse in the plug didn’t blow, the rcbo for the circuit didn’t trip either. Something amiss or fairly standard.
No earth in the cable.
No earth fault so no reason for the RCBO to trip, and in a short circuit scenario a typical MCD or RCBO won't trip until you exceed three to four times the rated current.
(Should add here that continuous overload is different).
SNAP!
I did the same last week, I thought I'd lost grip on the power button but then noticed I had a new cordless hedge trimmer...
This reminds me, need to fix it, going to use choc blacks and electrical tape, seems like a safe option to me, but happy to hear if it isnt!
I believe Mrs Dubs' fathers cable had a record of 4 of these at one point...
www.amazon.co.uk/pro-elec-pl09473-Connector-Rubber-orange/dp/9790834977/
Mine was near the handle so I opened up the body and re wired it with the remaining wire.
I think one other thing you need to be careful of is withstanding tension on the cable which a choc block won’t do.
Did you blow the fuse?
No earth fault so no reason for the RCBO to trip, and in a short circuit scenario a typical MCD or RCBO won’t trip until you exceed three to four times the rated current.
Unless the cut was extremely quick surely even the briefest direct short to neutral would have easily exceeded the current required to trip?
I too would be very surprised and would be a bit suspicious of whatever breaker was protecting it...
oikeith - it isn't safe.
After I did it (d'oh!), there was enough cable left to connect the remaining length directly into the hedge cutter. It was easy enough to open, and the terminals and strain relief clamp were easy to use.
If you haven't got enough length of cable left, you might consider buying some more - it shouldn't be too expensive.
Chocolate block and electrical tape would be a bit dodgy. For a kick off, I remember the electrician at work telling me that a lot of electrical tape he tested wasn't very good at insulating! Also, a chocolate block doesn't have any strain relief, so over time, the wires will probably work a bit loose, then one day, you might pull the cable more than you intended and have a live wire sticking out.
You can get proper blocks for joining electrical cables (they have strain relief clamps), but they are rather big and heavy. Not ideal for use on the area of cable that waves around when you use the hedge trimmer. Also could be more expensive than replacement cable.
For heaven's sake, don't try any of this unless you really know what you are doing.
(Not just think 'how hard can it be?')
Jingle
going to use choc blacks and electrical tape, seems like a safe option to me
I'm assuming that's a joke.
Unless the cut was extremely quick surely even the briefest direct short to neutral would have easily exceeded the current required to trip?
Painted / dirty / oily blade, flexing cable, long extension lead etc etc will all limit the current flowing through the short circuit. To trip instantly could mean a fault current of 120A, which seems unlikely through what might be a very small small contact area. The stands of copper would probably vaporise before they allowed that much current through.
There was a spark so definitely a short. Odd The fuse in the plug didn’t go which I assume is just a 5 amper but will check!
Personally, I'd repair with offset solder joints and heatshrink over both the inner wire and outer sheath insulation, although some people might not be tooled up for doing that.
Alternatively, there are many different types of in-line cable joints e.g. this one
A chocbox overwrapped with tape wouldn't technically conform to mechanical or ingress protection guidelines, however they DO have strain relief and DO NOT rely on tape for insulation (when dry and undamaged at least) so is at least a step above the typical bodge repair of bare screw terminal blocks and a bit of tape...
muddyjames
I think Flaperon made a good point, just above your post.
I'm not an electrician, but I worked a couple of years as a manufacturing engineer at a company making fuses for plugs.
It is best to remember that the fuse in the plug is just a thin piece of wire in a ceramic tube: precisely make, but that is all it is.
I think its purpose is mostly to stop fires from overheating of the appliance, its mains cable, extension cables, and the cables in your walls. That is all. It is not to stop people from being electrocuted.
It is designed to carry the rated current (plus a little bit for supply variation and manufacturing tolerance) without getting too hot.
If the current is much higher than rated (like if you clamp a big piece of metal across bare wires), then the fuse will blow, melting the wire inside the ceramic tube, making an open circuit, ever so quickly (milliseconds).
If the current is only slightly higher than rated (like if you add a light bulb to the maximum number of electric heaters already on an extension lead), the fuse in the plug for the extension lead could take much longer (minutes, if I remember correctly, maybe even hours).
Once I learned more about them, I was quite impressed how well they performed for the price!
I would guess (with a bit of relevant knowledge), that despite the impressive spark, your fuse didn't see a current high enough, for long enough, to melt the wire.
Do remember though - the fuse wouldn't care if you were electrocuted or not.
A current of as little as 30 milliamps can kill: Wikipedia page on Electrical injury
Jingle.
Done it myself - if the cut is quiick enough it won't trip. I've had it trip and not trip. Current cable is bright blue !
going to use choc blacks and electrical tape, seems like a safe option to me
I’m assuming that’s a joke.
my angle grinder i use at work has been like that for over a year, keep meaning to replace the cable as i have one but keep forgeting.
Choc blocks, tape, solder and heat shrink are all dodgy bodges liable to separate, crack or split and give you a proper shock.
Reterminate the shorter lead into the machine, replace the flex, or buy an in-line connector that you sometimes see on older lawn mowers. Just make sure you wire it so the exposed pin side is on the machine side so they are not live!
You can also get different versions and I've seen people cut all the leads off 50cm from the tool to make for easy storage and fit a inline connector, and then wire various extension leads of different lengths so they can mix and match cords and tools.