RCD Protection - Domestic TT installation Regulations

[crwBramley]

Right now I have an ancient Consumer Unit with all circuits, i.e. the whole installation, protected by a single 100ma RCD - which invariably trips during an electrical storm causing much annoyance - and thawed freezers when we're away. I was intending to have the consumer unit replaced and have each circuits protected by an RCBO. Nonetheless, I have been told today that because it is a TT installation with Rod Earthing, Regulations still require that the whole installation must be protected by a (100ma) RCD. ?? I'd be grateful for any comments about this.
Thanks.
CRWbramley[/b]

 

[JohnD]

It can be a time-delayed (type S) RCD which is less likely to be tripped by momentary surges like lightening.

Have you asked your supplier if they can provide you with an earth? Preferably a PME one? This is often available now even on overhead supplies, usually costing £60 to £100

 

[Cremeegg]

I assume you're near Bramley near Guildford - I know of many places around Guildford and south down the A3 where the DNO has been upgrading TT to PME on the overhead supply over the last few years - give them a bell - saves much hassle.

 

[RF Lighting]

If you RCBOed every circuit, then there is no need for a main RCD (providing the CU is insulated)

It is not going to be cheap, but if you can afford to do it like this, it is a superb way of doing things, and would minimise inconvenience in the event of a fault.


As has already been said though, check to see if PME is available to your property. The cost of upgrading your supply will be less than the additional expense of a special setup for a TT supply.

 

[crwBramley]

Thanks JohnD - also to Cremeeg and RF Lighting. Your comments suggest that with a PME earth, RCD protection would not be required if all circuits are individually protected by RCBOs. Why the difference?
In any event I will try a time delayed RCD in the first instance and also inquire about having EDF provide a PME earth.
Thanks again.
Chris Williams

 

[RF Lighting]

If you have you supply upgraded to a PME earth, then you will not require any RCD protection to low risk circuits such as lighting, cooker, water heater etc.

You will only need 30mA RCD protection to any socket which could supply equipment for use outdoors.


It is also a good idea to, and most electricians RCD protect ALL socket circuits (except in special circumstances), and circuits supplying things like showers etc

In any event I will try a time delayed RCD in the first instance and also inquire about having EDF provide a PME earth

You might be better off doing these the other way around, as it will save you needing to buy a 100mA TD RCD if you can get a PME upgrade.