TT issues with new house

Kickaha0884 · Jan 11, 2023

We have just moved into a house built in the 90's. So, I'm a retired electrician and was confused by the 4 x TT rods all connected within a metre of each other on one side on the house. I dont have any expensive test kit any more, but when I connected an electric fence energiser to the house earth I only got 1000v instead of the 7000+v. when I ran a test earth independent of the TT system I got the full voltage. I decided to put in a new 3/8 rod and therein lies the problem. The house is surrounded by rubble and you can hammer in a rod and then literally just pull it out again by hand. Nearest proper soil is 15m from the house. Any suggestions would be gratefully received. Ta.

DPG · Jan 11, 2023

I think a proper test of the rods would be in order. Is there any previous paperwork showing the Ze?

Diddy · Jan 11, 2023

4 rods would suggest that they struggled to get an acceptable reading from just the single one. BUT regardless if I were looking to install a rod and it was next to the house which is all rubble etc then id imagine my only real option would be to 1st dig out a hole then knock in rods with extensions on them until I hit "good" earth. Be careful of incoming services though. Possibly use the 1st earth rod and add extensions onto that while driving it further into the ground.

Kickaha0884 · Jan 11, 2023

DPG said:
I think a proper test of the rods would be in order. Is there any previous paperwork showing the Ze?

Thanks for your suggestion DPG. No paperwork at all. The previous owner was 16th an d did the wiring himself. Im guessing the Ze reading would be poor. The house is surrounded by rubble so I guess its a matter of resiting the rod and running the earth even if its som 15m?

Kickaha0884 · Jan 11, 2023

Diddy said:
4 rods would suggest that they struggled to get an acceptable reading from just the single one. BUT regardless if I were looking to install a rod and it was next to the house which is all rubble etc then id imagine my only real option would be to 1st dig out a hole then knock in rods with extensions on them until I hit "good" earth. Be careful of incoming services though. Possibly use the 1st earth rod and add extensions onto that while driving it further into the ground.

That sounds like a plan. the rod is meaty enough to take driving into the ground. I know from using the digger that the rubble is at least 2m deep. Im trying to remember if there is a distance limitation from the house to site a rod (V drop) do you think its feasable to run an earth cable 15m to good soil? appreciate your suggestion Diddly, thanks.

JBW175 · Jan 11, 2023

Can you speak to the DNO and see if it’s possible for them to upgrade your service an PME / TNC-S your earthing arrangement.

My mates done a load of building work
At his place and needed the service head moving. He originally had a TT arrangement supplied by overhead lines. The DNO PME’d it when they moved the service head. May be able to do the same with yours.

Kickaha0884 · Jan 12, 2023

JBW175 said:
Can you speak to the DNO and see if it’s possible for them to upgrade your service an PME / TNC-S your earthing arrangement.

My mates done a load of building work
At his place and needed the service head moving. He originally had a TT arrangement supplied by overhead lines. The DNO PME’d it when they moved the service head. May be able to do the same with yours.

Its a good thought. Its an odd supply arrangement here. Meter box is (vaguely) attached to a mobile home then run through to the house 30m away. The meter is 130m away from the nearest supply pole - but its a good idea and wont hurt to ask. Thanks JBW

robd · Jan 12, 2023

If you use the threaded 5/8" rods there is an SDS attachment you can get for driving them in

Kickaha0884 · Jan 12, 2023

robd said:
If you use the threaded 5/8" rods there is an SDS attachment you can get for driving them in

Oh thanks robd, thats useful info. Was going to smack them in with a mallet.........

Diddy · Jan 12, 2023

Kickaha0884 said:
Oh thanks robd, thats useful info. Was going to smack them in with a mallet.........

New century mate, we don't use mallets any more SDS does it all. Young apprentice electricians now wont have the biggest arms amongst their peer group and it's all down to the now humble sds.

Kickaha0884 · Jan 12, 2023

Diddy said:
New century mate, we don't use mallets any more SDS does it all. Young apprentice electricians now wont have the biggest arms amongst their peer group and it's all down to the now humble sds.

hahaha. Looks like Im now old school.............

pc1966 · Jan 12, 2023

Linian make some very handy accessories here. One is a rod-tip that is basically a masonry drill:

LINIAN Earth Rod Pro™ Bit, Carbide Tip (1LERPB)

LINIAN designed and developed a simple and effective solution that bores through hard top layers and underground rock to achieve a secure Earth Rod connection first time. This innovative, patented new solution offers installers confidence that they will be able to easily install the rod the...

linianclip.co.uk

And they do a matching SDS driver to make it easier to drive in:

LINIAN Earth Rod Pro™ Driver (SDS+) (1LERPD)

With the rise of new challenges like 5G, EV charging industry, Big Data installers are completing, even more, earth rod installations than ever before. However, this can be a laborious task, often involving a large hammer, a lot of effort, and hopefully a bit of luck. It doesn’t have to be this...

linianclip.co.uk

If you can get 8' in (two 4' rods with coupler) generally you get better results as ground tends to retain moisture lower down. However, if it really is dry rocky stuff all the way you might want to consider a trench to somewhere that has soil for a rod with better chance of success.

pc1966 · Jan 12, 2023

Seems CEF stock them (for the usual definition of "stock" at CEF of course):

Earth Rod Pro Drill Bit (Pack of 1)

Allows rapid earth rod installation when used with Earth Rod Pro drivers - sold separately [1LERPD] and [1LERPM]

www.cef.co.uk

Earth Rod Pro SDS+ Driver

Allows rapid earth rod installation when used with Earth Rod Pro drill bit - sold separately [1LERPB]

www.cef.co.uk

robd · Jan 12, 2023

I haven't used the tips are they any good? Roughly how much?

pc1966 · Jan 12, 2023

robd said:
I haven't used the tips are they any good? Roughly how much?

I haven't either, my last set of rods were M16 threaded stainless and I cut an tip using an angle grinder and then used a SDS adaptor and 1/2" drive stud nut runner to drive the thing in:

Stud Runner Socket 1/2" Drive – Metric Coarse Thread | Impact Socket

impactsocket.co.uk

They seem to cost about £20 each so not cheap, but ideal for stony or otherwise hard ground where the usual steel with copper cladding is just a bit too soft to be driven in the hard way.

Kickaha0884 · Jan 12, 2023

pc1966 said:
Linian make some very handy accessories here. One is a rod-tip that is basically a masonry drill:

LINIAN Earth Rod Pro™ Bit, Carbide Tip (1LERPB)

LINIAN designed and developed a simple and effective solution that bores through hard top layers and underground rock to achieve a secure Earth Rod connection first time. This innovative, patented new solution offers installers confidence that they will be able to easily install the rod the...

linianclip.co.uk

And they do a matching SDS driver to make it easier to drive in:

LINIAN Earth Rod Pro™ Driver (SDS+) (1LERPD)

With the rise of new challenges like 5G, EV charging industry, Big Data installers are completing, even more, earth rod installations than ever before. However, this can be a laborious task, often involving a large hammer, a lot of effort, and hopefully a bit of luck. It doesn’t have to be this...

linianclip.co.uk

If you can get 8' in (two 4' rods with coupler) generally you get better results as ground tends to retain moisture lower down. However, if it really is dry rocky stuff all the way you might want to consider a trench to somewhere that has soil for a rod with better chance of success.

Thanks for your advice. will get this bit and maybe have to hunt around for some more solid ground. When I was running my electrical business I vaguely remember you used to be able to buy something like a clay to goa around the rod - will have to have a look...........

DPG · Jan 12, 2023

Kickaha0884 said:
Thanks for your advice. will get this bit and maybe have to hunt around for some more solid ground. When I was running my electrical business I vaguely remember you used to be able to buy something like a clay to goa around the rod - will have to have a look...........

Bentonite I think it's called.