TT system eic minor point

[mhar]

New circuits. Ra of 229 Ohms therefore the rcds are for fault protection by design. Zdb of 0.29 (10mm gas bond) so are the rcds classed as additional protection?

 

[Wilko]

Hi - my take is - Reg 542.2.6 says gas pipes can’t be used as an earth electrode. So the design should be based on the TT earth rod result.

 

[Octopus]

The "advisory" range for TT RA is up to 200 ......... could you add a 2nd rod? (or water the ground?)

 

[The Ghost]

Put water with it...reminds me of a long time ago a team were putting in a gigantic earth rod. We used to put loads of salt and coke in the earth and then water it. We dug out the earth before hand and mixed it. One of the guys toward the end jumped on the "conditioned" patch and disappeared into the ground. At the time it was hilarious.

 

[davesparks]

Hi - my take is - Reg 542.2.6 says gas pipes can’t be used as an earth electrode. So the design should be based on the TT earth rod result.

The problem with that is the electricity won't read the book before deciding where to go.
With the values stated the gas pipework will carry the major part of any fault current to earth.

 

[Wilko]

Agreed.
Paperwork exercise I suppose, just in case gas gets converted to yellow plastic

 

[Deleted member 9648]

New circuits. Ra of 229 Ohms therefore the rcds are for fault protection by design. Zdb of 0.29 (10mm gas bond) so are the rcds classed as additional protection?

The RCD's will be for both fault and additional protection.

 

[davesparks]

Agreed.
Paperwork exercise I suppose, just in case gas gets converted to yellow plastic

That's not really where my line of thought was going, im wondering what the dangers are and what can be done?

 

[telectrix]

starter for 10.....improve the earthing with more rods or mats.

 

[ipf]

starter for 10.....improve the earthing with more rods or mats.

Might have a job on and cost a bit getting it down to 10, though....

 

[telectrix]

get 1 rod into the foul drain.that should bring the Ra down..

 

[chris day]

wait hang on a moment i will be doing more TT jobs in london with the car charger PME situation.
so what do i need for this.. some 12 litre of coke and salt? and this makes the ground soft?