Extension lead safety in garden?

[jim]

Please, what is current opinion on use of extension leads in the garden?

Focus of attention is a 650W electric hedgecutter plugged via a 30m extensi on lead into a 13A socket on a house 30A ring MCB/RCD protected circuit. Th e supply is PME if that is relevant. The hedgecutter is double insulated & its lead has only L & N cores - ie no earth, though the extension lead does carry an earth conductor. The extension cable is rated 10A, fully unwound - 3A reeled up.

So to get to the point: how well protected is the user from electric shock?

Are things improved or made worse by inserting one of those plug-in RCDs wh ich are often advocated for portable appliances? & if improved, where shou ld the RCD device be inserted - ie at the house socket or at the end of the extension lead?

TIA for any views.

[Fredxx]

If the circuit has an RCD, and it's been tested recently, then it's as safe as it's going to be.

At one time I thought you could get plug-top 10mA RCDs, or was I just dreaming?

[Andrew Gabriel]

Without an RCD, the earth fault loop impedance can be an issue. PAT test guidelines for extension leads with 13A fuse:

1.25mm² 12m max length 1.5mm² 15m max length 2.5mm² 25m max length (won't fit in most 13A plugs though)

They mustn't be daisy-chained to longer lengths.

By fitting a lower current fuse, you could in theory increase the cable length proportionally. The RCD removes the concern over earth fault loop impedance, but you may in theory end up with a short on the cable which takes long enough to blow the fuse that the cable gets damaged.

I have a dedicated outdoor socket circuit, and that's on a 10mA RCBO in the consumer unit. After a couple of accidents, I had to replace the hedge cutter flex anyway, and so I used 3-core, but the earth is not connected at the hedge cutter end. However, having it in the cable seemed to me like a good thing, as it increases the chance of an earth fault if the cable is cut (thereby tripping the RCD), and reduces the chance of the earth fault going through me whilst I'm balanced at the top of a ladder. I have managed to cut through the lawnmower cable without blowing a fuse or the RCD (probably too quick), leaving a live cable-end in the garden. I suspect that if I had the earth in the cable too like I do on the hedge cutter, that might have tripped the RCD.

[Dave Liquorice]

Agreed, test the RCD that covers the circuit in question with its test button. Remembering that everything else also fed through that RCD will also go off...

You could, I have one. It can be a right PITA to set if there is a long extension cable attached, the inrush can trip it...

[polygonum]

Glad you wrote that. I cannot get my head to believe that two cores are better than three. Maybe hardly any worse. Surely much of the double-insulated concept is about saving costs not enhanced safety? You could have all the protective aspects of double-insulation and still allow a cable to terminate with three connections within a device.

[ARW]

Petrol strimmers are the new garlic bread:-)

[Road_Hog]

They may be, but they will be about as useful as garlic bread, as the OP is attempting to cut a hedge.

[Jaffna Dog]

sion lead into a 13A socket on a house 30A ring MCB/RCD protected circuit. The supply is PME if that is relevant. The hedgecutter is double insulated & its lead has only L & N cores - ie no earth, though the extension lead do es carry an earth conductor. The extension cable is rated 10A, fully unwou nd - 3A reeled up.

I don't trust plug-in RCD's, or the ones built in to sockets, I've known bo th to fail to trip. The best solution is to protect all circuits with a pro per fixed RCD, this also applies to indoor use, with the ever-increasing us e of mains-powered gizmo's, many of them with dubious safety.

For outside extensions, I've fitted all our power tools and garden machines with 'commando' plugs, with a socket on the extension lead and a short ada ptor lead for use indoors. These provide much better protection against wat er.

which are often advocated for portable appliances? & if improved, where sh ould the RCD device be inserted - ie at the house socket or at the end of t he extension lead?

[Rick Hughes]

I have a RYOBI expand-it system .... gives me chain saw, strimmer & hedge trimmer ... and up to 9 foot extension. Great bit of it and push button start - never fails - instant.

[Dave Liquorice]

Do you mean the one feeding just the extension has failed to trip when on upstream with other circuits has? Think about it and it's obvious why that is frequently the case.

I'd rather that outside circuits had their own dedicated RCD be that in the consumer unit, part fo the socket used or a plugin one. Don't like the idea of something happening outside disconnecting stuff inside without warning.

[Jaffna Dog]

No, I mean physically jammed, and not tripping when the test button is pushed.

[ARW]

So do I.

And this is me pissed up using it for the first time