RCBOs . . . all tripping at same time.

[chocolate]

( 1 ) What would cuase a consumer unit, with RCBOs installed, to all trip out at virtually the same time, at about 7am every morning, but at no other time ?

It's a TT earthing system, with overhead supply cables linking the house to the pylon in the street. Then two cloth covered live tails from there to the main head. These rae the original cables and have been around since the beginning of time.

Could it be a fault with one of the LIVE conductors that link to the house from outside ?

The elecy board have had a look and are going to replace the two cloth cables with a new concentric cable ( like those used for PME connections ). All the circuits have been tested, and given the thumbs up. All RCBOs function correctly and in the correct operating times.

The elec board tested at the board. My tested Ze was 2.59ohms. They obtained a similar value, and concluded that it was far too big. For a TT supply, I reckon that's pretty darn great !!!!!!

( 2 ) Can I refuse to have a TNCS connection ( and request that no earth connection is provided ) and continue to use the earth electrode ????

 

[Mac]

Some sort of timer in the house,outside interference

 

[Matthew M]

The elec board tested at the board. My tested Ze was 2.59ohms. They obtained a similar value, and concluded that it was far too big. For a TT supply, I reckon that's pretty darn great !!!!!!

Your electricity board man seems not to have read the rules. for a TT system with RCD on all circuits the maximum Ze is calculated so that your earthed metalwork doesnt go over 50 volts while the RCD is being tripped by a fault, thus Ze is less than 50 volts/ 30 milliamps = 1666 Ohms. The regs does point out, though, that if your Ze is actually over 1Kohm then it is probably pretty unstable and you should get a longer or wetter earth spike.

 

[tacon]

just a few bits to think about

-have had rcd's trip in next property before on test, tt supplys
-on peak switches about 7 am earth leakage.
-rcbo in lower amps trip under zs test more often.tt supplys
-your live neutral zs not rod resistance under 0.35 get pme may stop tripping.