TT system issues???

[MilesSparks]

Hi,
I've had to change a TN-S over to a TT system.
My first problem is that my earth rod resistance is too high. At the moment it's measures at 161ohms (taken it wet conditions). To satisfy NICEIC I need to get it below 100ohms in normally dry conditions. What is the most effective way of doing this? Is it to install a second rod or extend the first rod deeper? At the moment my first rod is 8ft into the ground.
My second problem is the house was wired to 17th edition regs, supplementry bonding in the bathroom was not done as all ccts are rcd protected and all main bonding is in place. Is this now a issue now that the earthing system has changed to a TT system?

 

[MilesSparks]

I kind of gave up on them to be honest. Needed to get this job finished before Xmas- Client is getting ****ed off and I need paying!!!

 

[Engineer54]

Didn't have much choice, no earth at all!!! I thought putting a rod in was my best option tried contacting DNO but couldn't get a decent response.

What do you mean ...No Earth At All?? If it was a TN-S previously then you will still get Some reading?? And if it was an official TN-S connection, then the DNO are duty bound to maintain that earthing provision, if that means converting to a PME connection, then so be it!!

I kind of gave up on them to be honest. Needed to get this job finished before Xmas- Client is getting ****ed off and I need paying!!!​

​

What you Don't do, is give up on getting this sorted, you have what is known as a ''Duty of Care'' to and towards your client!! Bunging a rod in the ground, in this case a temporary fix at best doesn't cut it!! Whether you want paying or not!!

 

[MilesSparks]

Who said I'm giving up on getting this sorted??? I'm well aware of my 'duty of care' hence why I'm trying to get other people's opinions! I will try the DNO again, they're just not that helpful!

 

[telectrix]

i once had a problem with being fobbed off on the phone by DNO. 2 hours of talking to nobody thsat even knew what i was talking about. a recorded delivery letter addressed to " the chief suit who's going to lose his pension" worked wonders.

 

[bigbaddave]

Who said I'm giving up on getting this sorted??? I'm well aware of my 'duty of care' hence why I'm trying to get other people's opinions! I will try the DNO again, they're just not that helpful!

I would tend to hurry up at get it sorted then, Customer aint going to be too happy when they find out that your days + wages plus associated costs could have been avoided just becuase you gave up on getting the original fault sorted.

 

[MilesSparks]

What do you think I'm doing !!!! My Christmas shopping????

 

[shazbutz]

It makes a difference because this area is where all the old building rubble is going to be. The further away from building walls the better!!

So WHY have you had to TT this previously TN-S property?? And why didn't the DNO give you a PME connection if it was they're earth provision that failed??

I've recently had this type of issue, with a failed TN-S on the DNO side. Initially the call was flat handed away by the call handler but when I asked them to record it as a life threatening situation given the poor Ze, resulting poor Zs the impact on RCD activation times and requested his name and a reference number for the call things improved. It still took them 10 days to turn up and grudingly accept I was right and start digging up the road.
Unsurprisingly though they felt that PME connection and new head was "not necessary given the improvement in Ze"!!
Oh and we had the normal discussion of who cut the seals off the main fuse.....

 

[bigbaddave]

Well, how did the convo with the DNO go?

 

[LlandrilloSpark]

Lost track of TNS I've measured in last 3 years where Ze was in some cases >2000ohm and no voltage L-E, FACT - contact the DNO emergency line and they will be out within 24/48 hrs, I've edited no longed than that for sure visit and rectification.
In the words of DNO engineers "THere are probably thousands and thousands of knackered TNS earth connections in the UK, it's not til recently when you sparks are doing more testing that we actually know about them"

"TNS fail because the lead sheaf corrodes away underground "

 

[GLENNSPARK]

Well i'm assuming that the TN-S earth has failed on the DNO side, i hope so, or the OP is a fool!! lol!!

If you have an 8 foot rod that's only giving you 160+plus ohms in wet sodden conditions, then either the soil type in that area is naff, or your driving the rod through rubble and the like. Your rod position isn't right next to the house outside wall by any chance is it??

You have 2 choices really, 1) Try another rod position in a different area of the property, and at least a metre and a half or so away from any building walls. 2) leave it as it is, and install a S type 100 mA as your main CU switch/isolator.

You could also try as others have suggested add another 1.2m extension to the existing rod and see what that gives you, but as it is, standing at 8 feet, and only giving 160 ohms, i can't see it making much of a difference to be honest!!

The NICEIC don't make the rules thankfully, so ignore any such figures they may be putting forward. A 100 ohm Ra TT system is just as useless as the BS7671 numbty figure of 200 ohm's...

and if it is the DNO earth thats failed.....why didn`t get them to sort out their earthing arrangements that were being used and as such their responsibility rather than go down this route.......or no doubt the DNO lass on the end of the phone told him to rod it....or else..lol..