Ra Reading?

[067256]

Hi there,
Been to quote a new DB change today...whilst inspecting the installation there are some things that need addressing.( TT System) The main problem was an Ra reading of 748 Ohms!!
Can this simply be sorted out by adding another electrode, or driving in a deeper one?
Thanks.

 

[a1guvner]

Hi there,
Been to quote a new DB change today...whilst inspecting the installation there are some things that need addressing.( TT System) The main problem was an Ra reading of 748 Ohms!!
Can this simply be sorted out by adding another electrode, or driving in a deeper one?
Thanks.

Where was the rod located, Sheltred? dry area? etc

Was it a proper 3 lead test?

 

[067256]

rod located outside kitchen door....not sheltered but surrounded by bushes, thats all.

 

[067256]

Yes with main earthing conductor disconnected.

 

[a1guvner]

A deeper rod can only improve the reading, or get the watering can out,

 

[MarkieSparkie]

[FONT=&amp]The depth of a vertical rod is the decisive factor for stability as the effects of drying and freezing effect the upper part of the rod most significantly. Therefore a 3m rod with a Ra=200 Ohms will be more stable than a 1.5m rod with a Ra=100 Ohms.[/FONT] Although the regulations suggest Ra should be below 200 Ohms for stability it's good practice to aim for less than 100 Ohms to allow sufficient headroom for seasonal changes of environmental conditions. Use good quality 5/8" coupled rods in an inspection pit for mechanical/corrosion protection of the termination.