pro's advice needed

[daiplayer]

earth rod spacing : interesting . earth rod length = space distance . is that apllicable to terraced houses both TT ?

 

[Guitarist]

Best option is to see if you can get a free upgrade to TNC-S, then upgrade main earthing to 16mm and main bonding to 10mm.

 

[telectrix]

if using 2 rods, they should be spaced 1.5 x the rod length.

 

[Taylortwocities]

earth rod spacing : interesting . earth rod length = space distance . is that apllicable to terraced houses both TT ?

It's a black art, and not aprecise science. Have a look at this paper Bringing Grounding Down to Earth | content content from Electrical Construction and Maintenance (EC and M) Magazine

I am sorry that it is American but Figure 2a and text gives a decent overview of overlapping effective resistance areas. Enjoy!

 

[Octopus]

For the cost of a couple of 5/8's rods and a connector and new piece of 10mm GY I'd be putting a new rod in, further from the house.

 

[sedgy34]

i would see if dno can make it a tncs and 10mm bonding to incoming services

 

[SPARTYKUS]

might take 6 weeks though. Might be easier ter get the cheque by banging in Rods.

Whats this about black art I thought that was the spreads domain

 

[Rockingit]

Its a TT with a Ze of 207 , ( high i know ) what can i do about this ? inform dno :- convert to TNC-S?

Any way : PEFC : 1.11 a , ( LOW ) PSCC 1.2KA . HIGHEST Zs in house 3.43 , existing bonding 6mm .

As a rule of thumb ive heard of people using 0.5 of main supply tails : 16mm .

However if i inform the DNO of the high Ze and they convert to TNC-S , pefc will rise to eg: 230/0.35 : 657A min.

Any ideas ? or can show me how to do the adiabatic with this ?

I think you need to sit down with your calculator and revisit some of these sums and your testing..... if you have a Zs of 3.35 when you have a Ze of 207, then that means you have an R1R2 value of -203.65. Now that's a cable I'd really love to know where to buy.

The low pfc values that you get on TT installs are part of the reason for the requirements for RCD protection; it is realised that you will never get anywhere near disconnection times with that little current.

To lower your Ra then as others have said, bang in some nice LONG 5/8 rods down to at least a couple of metres.

 

[malcolmsanford]

Parallel paths with that bonding and all the CPC I would guess be the reason he as got a low Zs there RT

 

[Rockingit]

Parallel paths with that bonding and all the CPC I would guess be the reason he as got a low Zs there RT

That was my first thought as well, but in which case you'd surely then expect a Pefc of around 50-70A based on those figures?! Although..... 1.11A x 230V = R255 = 207 + 48 (roughly). But then again, you wouldn't be getting r1r2 value of 48ohms..... So, methinks some double checking in the testing department might still pay dividends.

Happy to be proved wrong, it's just the numbers leapt at me straight away!!