TT earth results

[sparkymalarky]

BS7430 - Earthing for generator 20 ohms or less for Ra.

 

[brightspark26]

You will love this One. Years ago our supervisor made another tradesman get the value under 200 ohms on a site being supplied via a big generator. They couldn't get the value down so they ennded up getting old crash barriers buried to try and get under the 200 ohm value. So basicly the earth spike is just protecting the generator frame and needs no value recorded ?

 

[davesparks]

BS7430 - Earthing for generator 20 ohms or less for Ra.

Thanks

 

[davesparks]

You will love this One. Years ago our supervisor made another tradesman get the value under 200 ohms on a site being supplied via a big generator. They couldn't get the value down so they ennded up getting old crash barriers buried to try and get under the 200 ohm value. So basicly the earth spike is just protecting the generator frame and needs no value recorded ?

The earth spike isn't protecting anything. It is providing the earth reference for a TNS supply. It ties the neutral point of the generator to the potential of the earth.

 

[brightspark26]

How could we ever get it to 20 ohms when we can't get it to 200

 

[davesparks]

How could we ever get it to 20 ohms when we can't get it to 200

Multiple deep driven rods, ufer earthing, soil treatment, bonding structural steel, earth tapes or plates

 

[brightspark26]

Say the site is in the middle of nowhere and the ground is mostly rocks. It's not going to happen easily

 

[davesparks]

Say the site is in the middle of nowhere and the ground is mostly rocks. It's not going to happen easily

So? Just because it's not easy it doesn't mean it's not possible. What if the building has an LPS? That will have to have a sub 10ohm overall Ra.

 

[brightspark26]

Generally portacabin type sites just plug and play