100mA RCD Incomming NOT TT but PME

[Chrishands]

Hi as the title suggests,

I know of a Fuse Board, that has a 100mA RCD incoming However its not a TT system its a PME system, I've only been in the trade 2 years now so im still green, did it used to be the case that 100mA was the standard instead of 30mA protection for Domestic Dwellings?

Thanks,
Chris

 

[jackhammerJIM]

No never has been . Could have been a TT converted to PME

 

[Simonslimline]

Hi as the title suggests,

I know of a Fuse Board, that has a 100mA RCD incoming However its not a TT system its a PME system, I've only been in the trade 2 years now so im still green, did it used to be the case that 100mA was the standard instead of 30mA protection for Domestic Dwellings?

Thanks,
Chris

No. A 100ma RCD offers no additional protection. it has probably been converted to PME as Jackhammer mentioned.

 

[Chrishands]

No. A 100ma RCD offers no additional protection. it has probably been converted to PME as Jackhammer mentioned.

I Thought so, but why? why notjust PME in the 1st place?

 

[Leesparkykent]

I Thought so, but why? why notjust PME in the 1st place?

Because pme probably wasn't available at the time.

 

[telectrix]

probably because pme was not available at the time.

 

[Marvo]

Would it have been installed to protect meter tails that are chased in and < 50mm deep?

**EDIT** This is a wild guess by the way, I don't work to BS standards so I'm not very familiar with them.

 

[davesparks]

Would it have been installed to protect meter tails that are chased in and < 50mm deep?

**EDIT** This is a wild guess by the way, I don't work to BS standards so I'm not very familiar with them.

Nope, that's a very recent addition to the regs and only allows 30mA protection to be used for this

 

[davesparks]

I Thought so, but why? why notjust PME in the 1st place?

A lot of places had TT systems until the old overheads were replaced then PME was installed but obviously all the installations remained the same.
Or it's possible that someone didn't know what they were doing, didn't understand or thought that replacing a 30mA with a 100mA was a good way to cure nuisance tripping

 

[Marvo]

Thanks for clarification Dave, just a thought.

 

[baldsparkies]

Having a look around can often reveal an old copper twig sticking out the ground some where.
Although its possible for those earthing arrangements to be tagged off old lead water pipes.
Looks of horror these days, but our parents and grandparents managed to survive such ordeals all there lives and through to old age with no ill affects.
Regulations change and don't we know it, but remember our senior citizens were more concerned with German bombers rather than dodgy electrics.

 

[JD6400]

Hi as the title suggests,

I know of a Fuse Board, that has a 100mA RCD incoming However its not a TT system its a PME system, I've only been in the trade 2 years now so im still green, did it used to be the case that 100mA was the standard instead of 30mA protection for Domestic
Thanks,
Chris

Hi Chris , what type of property is it in ?

 

[Midwest]

probably because pme was not available at the time.

Its a bugger when someone beats you to it, isn't it. :26:

 

[Deleted member 26818]

I have known on instances where a DNO will install a 100mA RCD (which then becomes the property of the consumer), where installations are very close to sub stations and have very high PFC and PSSC.

 

[JD6400]

I have known on instances where a DNO will install a 100mA RCD (which then becomes the property of the consumer), where installations are very close to sub stations and have very high PFC and PSSC.

I have had that that happen at least twice that I can remember .