Do RCDs actually work?

[ARW]

What were you holding the probes to?

[ARW]

Does suggest 20mA is the danger point.

[Andrew Gabriel]

[Andrew Gabriel]

That's partly true, but some US sockets do have a daisy-chaining terminal for connecting more sockets to the RCD protected side (a stunningly good idea which I haven't seem here, although it wouldn't work on a ring circuit).

The other issue is that with 120V mains, lower currents appear to be fatal and it can be difficult to generate 30mA without having good body contact, so somewhat counter-intuitively, you need lower trip current to provide same degree of protection with 120V.

For my outdoor socket circuit, which is only used for the lawn mower and hedge cutter (at top of tall ladder), I have that on a 10mA RCD protected TT circuit. With only one appliance in use at a time, mutiple leakage isn't an issue, and I prefer the idea of 10mA protection when I'm hanging off the top of a ladder with the hedge cutter.

[John Rumm]

Worth keeping in mind that RCDs don't limit the shock current - only the duration. So the injury from a 50mA shock will be the same from a 10mA trip RCD as from a 30mA one.

[John Rumm]

What, by sticking a leg bone through it? ;-)

[ARW]

Having a milk float parked on his head may not have helped things. Was he called Jack? I'll get my coat.

[PeterC]

The other set that isn't recorded, I'll bet, is the injuries sustained when a minor shock - RCD trips - lights go out - panic, drop tool/fall (off) scenario happens. That's why I like my split CU where the lighting circuits are on a 100mA RCD.

[Robin]

Fair cop. I meant to add soemthing like "without ending up with a product the general public won't buy". I've never seen one with a low profile. And I see that the instructions for the 1 gang example warns you may need to "bend back the upper and lower fixing lugs to enable the RCD to be fitted".

[Robin]

Ooo yes.

Which begs the question why it is so hard to buy a 10mA plug-in RCD in the UK (other than off eBay from China perhaps).

[John Rumm]

They may well get recorded as a trip or fall, rather than being associated with the actual cause.

Generally death rate is a poor metric to use in electrical accident cases since there are (thankfully) too few to be significant. Injury rates are far higher - but probably get less rigour of classification.

[sm_jamieson]

[Andrew Gabriel]

This one is a 10mA RCBO, which was special order and specially expensive! (MEM/EATON Memshield2 - they only manufactured the 10mA RCBOs to order.)

But I agree on the lack of availability of 10mA RCDs - they used to exist.

I've been trying to suggest what portable equipment a volunteer repair organisation should use for mains distribution, and I would love to suggest 10mA RCDs for use where equipment is being run with covers off, but the only one I'm aware of is now EOL (as well as being bulky and power hungry).

(Isolating transformers are out of the question - the kit has to to be carried by hand across London and wider afield.)

[Johny B Good]

Strangely reminiscent of the reasoning behind the "Five A Day" dietary advice by HMG and the "Ten A Day" advice offered by the French Government to their citizens. :-)

[Adam Funk]

IIRC, back boxes in the US are usually 2 inches deep --- luxury.

[Dave Plowman (News)]

They need to have plenty room for that fire to get a hold. ;-)

[PeterC]

Does seem strange, as I was told (years ago) that hospitals use 10mA RCDs.

[The Medway Handyman]

Apparently the 5 a day was as much as they thought it was possible to get Brits to eat...

[John Rumm]

Smaller trip thresholds are often specified for use near livestock, since larger quadrupeds can be more sensitive to electric shock than us (wide feet spacing etc)

[JimK]

Snip

So why did I build machines to put 25W into patients at 500KHz then if DC would do?

Theo /q

Bless him it's not been the kindest of weeks gaffe-wise, must be the heat?

Jim K