Donate to Remove ads

Got a credit card? use our Credit Card & Finance Calculators

Thanks to johnstevens77,Bhoddhisatva,scotia,Anonymous,Cornytiv34, for Donating to support the site

Operation of RCD

Does what it says on the tin
MyNameIsUrl
Lemon Slice
Posts: 474
Joined: November 4th, 2016, 1:56 pm
Has thanked: 1304 times
Been thanked: 107 times

Operation of RCD

#397735

Postby MyNameIsUrl » March 21st, 2021, 7:35 pm

I have a Wylex WSEM 80/2 ‘residual current operated circuit breaker’ 100mA trip mounted at the side of my consumer unit – it’s been there at least 25 years.

Whenever I need to switch the power back on, sometimes it takes several attempts to get it to latch on, and I have to lift it very gently and slowly. Is this normal behaviour? Obviously if appliances/lighting/heating are switched on, I’m switching a current, but should the switch just snap back on or is it normal to need easing back on?

(I have to switch the power back on with this RCD rather than the consumer unit switch, because switching the consumer unit on trips the RCD.)

csearle
Lemon Quarter
Posts: 4764
Joined: November 4th, 2016, 2:24 pm
Has thanked: 4812 times
Been thanked: 2083 times

Re: Operation of RCD

#397741

Postby csearle » March 21st, 2021, 8:04 pm

MyNameIsUrl wrote:I have a Wylex WSEM 80/2 ‘residual current operated circuit breaker’ 100mA trip mounted at the side of my consumer unit – it’s been there at least 25 years.

Whenever I need to switch the power back on, sometimes it takes several attempts to get it to latch on, and I have to lift it very gently and slowly. Is this normal behaviour? Obviously if appliances/lighting/heating are switched on, I’m switching a current, but should the switch just snap back on or is it normal to need easing back on?

(I have to switch the power back on with this RCD rather than the consumer unit switch, because switching the consumer unit on trips the RCD.)
In my experience there could be two reasons for this.

1. Your RCD is becoming faulty in the sense of being over-sensitive.
2. Your electrical installation is slowly developing a fault.

That kind of RCD is employed when the electrical installation is deriving its Earth from an Earth stake hammered into the ground (or sometimes uses the water or gas service pipes to provide the Earth).

The installation is usually out-of-town.

My first fault-finding mission would be to individually turn off circuits to see whether turning off one of them in particular removed the issue you are experiencing.

If that didn't indicate a faulty circuit I'd do the same with each circuit's neutral also being disconnected at the same time.

If that didn't help I'd attach a sensitive clamp meter around the installation's tails to try to detect an imbalance whilst disconnecting stuff.

If that all didn't help, with your permission, I'd buy a replacement RCD (probably on eBay) and try that.

Chris

csearle
Lemon Quarter
Posts: 4764
Joined: November 4th, 2016, 2:24 pm
Has thanked: 4812 times
Been thanked: 2083 times

Re: Operation of RCD

#397744

Postby csearle » March 21st, 2021, 8:13 pm

MyNameIsUrl wrote:Whenever I need to switch the power back on, sometimes it takes several attempts to get it to latch on, and I have to lift it very gently and slowly. Is this normal behaviour??
No.
MyNameIsUrl wrote:Obviously if appliances/lighting/heating are switched on, I’m switching a current, but should the switch just snap back on or is it normal to need easing back on?
The former. C.

jfgw
Lemon Quarter
Posts: 2539
Joined: November 4th, 2016, 3:36 pm
Has thanked: 1097 times
Been thanked: 1146 times

Re: Operation of RCD

#397766

Postby jfgw » March 21st, 2021, 9:50 pm

csearle wrote:My first fault-finding mission would be to individually turn off circuits to see whether turning off one of them in particular removed the issue you are experiencing.

Alternatively, switch off all of the circuits first and see if that makes a difference. If it does, switch them on one at a time. Bear in mind that it could be the sum of several leakages causing the problem.


Julian F. G. W.

Mike4
Lemon Half
Posts: 7084
Joined: November 24th, 2016, 3:29 am
Has thanked: 1637 times
Been thanked: 3793 times

Re: Operation of RCD

#397804

Postby Mike4 » March 21st, 2021, 11:49 pm

jfgw wrote:
csearle wrote:My first fault-finding mission would be to individually turn off circuits to see whether turning off one of them in particular removed the issue you are experiencing.

Alternatively, switch off all of the circuits first and see if that makes a difference. If it does, switch them on one at a time. Bear in mind that it could be the sum of several leakages causing the problem.


Julian F. G. W.


^^^This^^^

Bear in mind it seems to be human nature when a safety device trips, for the human to imagine the safety device is faulty. As opposed to doing its job correctly.

DrFfybes
Lemon Quarter
Posts: 3731
Joined: November 6th, 2016, 10:25 pm
Has thanked: 1171 times
Been thanked: 1964 times

Re: Operation of RCD

#397987

Postby DrFfybes » March 22nd, 2021, 2:23 pm

Mike4 wrote:Bear in mind it seems to be human nature when a safety device trips, for the human to imagine the safety device is faulty. As opposed to doing its job correctly.


There is a reason for this though - safety systems are generally just that - used in an emergency, Consequently they tend not to be activated often, and I suspect the vast majority are rarely tested (who here has tested their consumer unit RCD in the last 2 years). Overpressure relief valves stick as systems don't go overpressure, then when you test one the bloody thing drips for days and you have to keep topping the system up and testing it to try and flush it out to get it to reseat. How often do you stand on the brakes to make the car ABS kick in? And as for that fire extinguisher in the garage, yes, you know the one, in the corner, under the old offcuts of wood, so encrusted in dust and spider webs that you can't tell if it is foam or dry powder. I know the dial is still in the green bit, but will it still work when you need it?

I've had 2 faulty domestic RCD trips in the last 10 years, and found one on Friday supplying the showers that doesn't trip when the test button is pressed. Also get sporadic ABS warnings on the car, and had other instances of safety systems acting unnecessarily putting the car in 'limp home' mode (failing overheat sensor). The thermocouple that turns off the boiler when the pilot light goes out is a good example - you must have replaced hundreds of those that had burnt out over the years (although it was probably also the only time half the boilers got a proper clean and service).

Anyway, I'm off to the garage to dust of my old fire extinguishers, stare at them for 5 mins, before putting them back in the corner and continuing to rely on fleet foot, working smoke alarm[1], and insurance should something catch alight.

Paul
[1] Remember the button only tests the battery and the buzzer, not that the sensor works.

csearle
Lemon Quarter
Posts: 4764
Joined: November 4th, 2016, 2:24 pm
Has thanked: 4812 times
Been thanked: 2083 times

Re: Operation of RCD

#398123

Postby csearle » March 22nd, 2021, 11:11 pm

I've come across about four RCDs in the last 12 months whose contacts have stuck and so didn't trip as the Test button was pressed. The recommended thing to do apparently is to replace them (rather than just get them functioning correctly again by actuating them).

The number of periodic inspections I'm doing has shot up recently as some new rules come into force about the responsibilities of landlords. I'm doing two tomorrow near Oxted. Maybe I'll come across some more sticky RCDs?

Chris

csearle
Lemon Quarter
Posts: 4764
Joined: November 4th, 2016, 2:24 pm
Has thanked: 4812 times
Been thanked: 2083 times

Re: Operation of RCD

#401098

Postby csearle » April 2nd, 2021, 12:31 pm

csearle wrote:I've come across about four RCDs in the last 12 months whose contacts have stuck and so didn't trip as the Test button was pressed. The recommended thing to do apparently is to replace them (rather than just get them functioning correctly again by actuating them).

The number of periodic inspections I'm doing has shot up recently as some new rules come into force about the responsibilities of landlords. I'm doing two tomorrow near Oxted. Maybe I'll come across some more sticky RCDs?

Chris

Edit: "now about five"


Return to “Building and DIY”

Who is online

Users browsing this forum: No registered users and 10 guests