RCD Protection Question......

[Pete E]

I live in a house built in the early 90's with the old colour code wiring. The MCB's in the CU are split over two RCD.

The socket outlets are all on one Ring Final circuit which covers upstairs and downstairs plus the integral garage.

I use one of the sockets in the garage as a supply for the electric lawn mower via a plain jane extension lead.

Last year, while cutting the grass while it was a little damp, I got a very slight "shock" (more a tingling sensation )...this did not trip the RCD ...The mower was on its last legs anyway, so I replaced it and all has been fine since. I also manually tested the RCD's in the garage and they tripped ok..

However, with grass cutting time getting closer, I am just wondering if any additional RCD protection would be wise? If so, would it be best to change the socket out let to a dedicated RCD one or get an RCD extension lead?

Our little grandson like to "help" in the garden, and I want things to be as safe as practically possible..

 

[Octopus]

Having rcd's in series doesn't really hemp.

Tingling could be symptomatic of an earthing issue ......

Do you have any test kit?

 

[Jim90]

When you say you tested the RCD you mean the ‘T’ button on the RCD? If so, it only tests it mechanically.

Probably best to get your place tested if you’re concerned!

 

[Wilko]

Hi Pete - agree with @Murdoch having another RCD in series won't help. But you could get the existing RCDs properly tested (the test button push is a start, but not the end of testing). Just FYI, a current that causes the RCD to trip will more than tingle if it goes via your-good-self.

 

[David M]

As Murdoch says. Its worth getting the rcd tested electrically and also get the earthing checked. A rcd will not operate correctly if the earthing is not adequate, since it measures an imbalance via "earth leakage" current.

 

[Pete E]

Having rcd's in series doesn't really hemp.

That's what I was wondering or whether I could get an additional RCD with a lower trip current?

Tingling could be symptomatic of an earthing issue ......

Do you have any test kit?

I think you are right about the earthing and if I am honest, the lawn mower and its lead were well past their sell by dates and I was just being a tight arse not replacing them earlier...The mower was replaced and the problem did not re occur and I've not had any other issues with that socket before or since.

Really my enquiry is "precautionary" ie is there anything I can do make things safer?

 

[Risteard]

A rcd will not operate correctly if the earthing is not adequate

Can't agree there. If the live conductors are imbalanced due to current going to Earth through you this will still be seen by the RCD.

 

[westward10]

I doubt the earthing is an issue as I suspect the mower to be double insulated.

 

[Octopus]

Most mowers don't have an earth connection

 

[Pete E]

I should add I did check the socket with a plug in socket tester, then visually, and then double checked the earth continuity with a multi meter back to the house. I also (later) tripped the RCU with a borrowed tester which had that facility, and it worked fine...

99% sure the culprit was the poor condition of the lawn mower...

 

[Pete E]

Most mowers don't have an earth connection

I think I was the earth connection at that point!

Would the resistance of long extension lead combined with mowers own lead cause any issue to prevent the RCD tripping if the current was only small?

 

[westward10]

I suspect this is the case of a damp electrical appliance and insufficient current to activate the rcd.

 

[Pete E]

I suspect this is the case of a damp electrical appliance and insufficient current to activate the rcd.

If I am honest, the whole set up/circumstances could have been a poster for "Not what to do..." and I think I was lucky only to get a tingle, but lesson learned!

 

[telectrix]

use this as the socket for mowers etc. it's 10mA trip current . more safety and hopefully this will trip before the RCD in the CU trips.

PowerBreaker RCD Single Socket - http://www.greenbrook.co.uk/sockets-switched-10ma-powerbreaker-rcd-single-socket-1016

 

[Pete E]

use this as the socket for mowers etc. it's 10mA trip current . more safety and hopefully this will trip before the RCD in the CU trips.

PowerBreaker RCD Single Socket - http://www.greenbrook.co.uk/sockets-switched-10ma-powerbreaker-rcd-single-socket-1016

That's the sort of thing I was thinking of, just for a "belts and braces" approach...Edited to adit looks like they have a stockest local to me as well...

 

[Taylortwocities]

A 10mA RCD in series with a 30mA one? Pointless, IMO.
The 10mA will only trip if the leakage current is more than 10 and less than 30mA. An earth leakage of more than 30mA will trip one, or the other, or both.
The reason 30mA is chosen is to reduce the potential of your heart going into fibrulation in teh event of a shock situation.
The RCD that you have is providing protection for all of the sockets in your house, and that means all the people in your house too.

Don't buy a 10mA RCD just to make you feel safer mowing the lawn. Have an electrician run an RCD tester on your 30mA RCD, and then you'll know the whole family will be protected in the event of something going wrong.

 

[telectrix]

sorry mate. i disagree. 10mA through your body is far less painful than 30mA. the discrimination may be an issue. give you that. also, given the fact that 90% of RCDs aren't even tested with the test button more than once in a blue moon, i stand by my post.

 

[Pete E]

sorry mate. i disagree. 10mA through your body is far less painful than 30mA. the discrimination may be an issue. give you that. also, given the fact that 90% of RCDs aren't even tested with the test button more than once in a blue moon, i stand by my post.

To add to that, I'll mention the bit about my grandson again...In the event of an accident, I'd much rather an RCD trip at 10mA than nearer 30mA..

I know no system is perfect, but for the small cost of the RCD outlet, I don't think I have anything to loose.

Just had a quick look in the garage, and I can add an FCU into the existing cable run very easily and then drop a short length of cable to the new RCD socket....Another advantage is that the location of the RCD will negate the need for me to use an extension lead....

 

[Midwest]

The Beama RCD Handbook is a good read for those long windy rainy nights. Page 11 gives some guidance of the effects of electricity on the human body.

 

[Midwest]

PS I can't see how anyone can get tingles for a Class II insulated lawnmower wearing suitable protective gloves, footwear, eye & ear protection, hi vis vest & safety helmet?

Been doing it in flip flops & shorts, have ya!