Retrofitting RCDs

[andy_g]

How hard would it be to DIY retrofit RCDs to a quite old consumer unit?

I attach a photo, I was thinking is there a matching RCD to replace the main on/off switch? If yes, how would I bypass it if it tripped all the time?

The photo shows the left hand side consumer unit, it does the lights and the washing machine, whereas there is a larger one on the right which does the power sockets etc.

 

[333rocky333]

You could not safely do anything with that board, it would be pointless

 

[sparkwright]

No sensible way to fit RCDs to all those circuits without replacing the consumer unit(s).

Considering those were the most common consumer units, you can't get RCD main switches or RCBOs to fit.

You could fit stand-alone RCDs outside of the board, but a new board is the answer.

 

[sparkwright]

MCBs are available to fit those boards, but not RCDs. MCBs wouldn't provide RCD protection, so MCBs would be pointless.

 

[EFLImpudence]

how would I bypass it if it tripped all the time?

You wouldn't. You would repair the fault.

 

[ban-all-sheds]

How hard would it be to DIY retrofit RCDs to a quite old consumer unit?

I attach a photo, I was thinking is there a matching RCD to replace the main on/off switch? If yes, how would I bypass it if it tripped all the time?

So you seem to have a seriously exaggerated fear of inadequate earthing of your PME supply, leading you to want an RCD, and then you posit bypassing it if it starts to work properly.

Barking.

 

[ericmark]

I have done just that with a Wylex board like the one you show, I have an 8 way DIN rail box above the two Wylex boards and two RCD's in that box one feeding each board, this was done back in 1990's when RCD consumer units with more than one RCD were rare, I did not want a 100 mA RCD and I did not want whole house on one 30 mA RCD so this allowed me back in the 90's to have a board similar to what is fitted today, I have a modern board ready to replace it when I get time.

The work fitting a box and RCD's and wiring it all up today is a non starter, the ready made consumer units are now made of steel and have all the buzz bars and rails built in, when I did it I had never seen a twin RCD consumer unit, and RCBO's were always two modules thick, and the RCD was four modules thick, in both cases now half the thickness.

 

[andy_g]

Thanks for the comments and suggestions, much appreciated.

I was hoping for a one for one replacement of the existing switches with an RCD switches to make it an easy job...

My post about earthing stems out of real curiosity, and now I have read on it and it appears it is a PME installation.

I am still not sure how one would know, without an RCD, that an appliance/anything somewhere in the house does not have a neutral to earth fault?

If such a fault exists undetected on a old installation like mine, then would having multiple earth points be better than having just the one ? Do I already have some kind of earthing indirectly due to underground water pipes? I know it says that it's meant to be floating, but if it is buried underground how can it be?

The comment about an RCD bypass is because I have seen installations (admittedly another country), old and new, having such a bypass switch next to the RCD on the consumer unit. Maybe it is some kind of regulation and they are obliged to offer it?

 

[Taylortwocities]

Some outline responses

I was hoping for a one for one replacement of the existing switches with an RCD switches to make it an easy job...

per the above, there is no such thing for your ancient board. If you need RCD protection then either replace the CU for an RCD one, or add RCD(s) externally to circuit(s).

I am still not sure how one would know, without an RCD, that an appliance/anything somewhere in the house does not have a neutral to earth fault?

An RCD is NOT a fault-finding device. It is there to provide protection SHOULD an earth fault occur.
If you are concerned about the possibility of an earth fault on your wiring, then you need an electrician with an INSULATION RESISTANCE tester. That can identify if a problem exists in teh wiring.

If such a fault exists undetected on a old installation like mine, then would having multiple earth points be better than having just the one ? Do I already have some kind of earthing indirectly due to underground water pipes? I know it says that it's meant to be floating, but if it is buried underground how can it be?

existing water and gas pipes are no longer used as the main method of earthing. Earthing is provided (in your case) by the electricity supplier. The Multiple Earth term relates to how the supply is provided to your property. In a PME (TNC-S) supply, the earth and neutral are combined and the earth/neutral is tied to earth at several points on the cable route from the substation to your house.

More about this at https://www.tlc-direct.co.uk/Book/5.6.1.htm

The comment about an RCD bypass is because I have seen installations (admittedly another country), old and new, having such a bypass switch next to the RCD on the consumer unit. Maybe it is some kind of regulation and they are obliged to offer it?

Maybe Johnny Foreigner might like to do this (where the average maximum age is below 40) but not here, where we know what we are doing.


So, get your stuff tested, if you are concerned about the age of your installation, and/or what is connected to it.
Ask a competent electrician to carry out an EICR. He'll probably recommend you update your consumer unit.

 

[EFLImpudence]

I am still not sure how one would know, without an RCD, that an appliance/anything somewhere in the house does not have a neutral to earth fault?

I think you are missing the point of RCDs.

Except when there is no alternative as far as the installation is concerned, they are for personal protection.
That is - when you become the earth path.

 

[bernardgreen]

they are for personal protection.
That is - when you become the earth path.

They also operate to reduce the risk of fire when there is a fault path to ground via a thin conductor that would be glowing red hot without the MCB tripping on over current.

 

[JohnD]

and often cut the power when there is any fire, not just an electrical fault, which starts melting insulation.

 

[EFLImpudence]

Is that not supposed to be prevented by correct design?

What current sufficient to melt the cpc will not trip the mcb?

 

[bernardgreen]

What current sufficient to melt the cpc will not trip the mcb?

It is not the CPC that melts. It is the stray bit of wire or other conductive material which connects itself between Live and Ground due to fault or damage.

 

[Risteard]

Is that not supposed to be prevented by correct design?

What current sufficient to melt the cpc will not trip the mcb?

I have seen it where a neutral tail hasn't been connected and due to a neutral/earth fault within the installation the entire return current for the installation has had a path back to the PEN conductor giving the appearance of the installation operating correctly but cables being severely burnt. A circuit breaker/MCB won't detect this because the phase conductor for each circuit is not overloaded.

Needless to say there was quite a bill for me finding and sorting out the problems!