TT Issue - High reading on TT

[Theorysparky]

Im doing some work in a house that is 40 miles away so i am trying to keep the travelling down.

no earth at the existing board (middle of the house) so i found a route out to the rear garden.I told the customer(a mate) that he needed to put a rod in no problems

it went down about 18 inches then hit rock,,,,pulled it out drilled down through rock another 12inches......

i took a reading and got 858 ohms

i am back there tomorrow to change the board (dual) but may not have time to relocate the rod

would you guys be happy to use the rod in the mean time until i am back there in a few weeks on another local job ????

858 x 0.03 = 25 so well within the rquirements of reg 411.5.3

its just the stability issue.

when i did a zs on the existing board i got 575 ohms on trip lock !!!!! better than the rod..

 

[Andy™]

providing 30mA RCD, then your well within the 1666 ohms Zs limit for that

short term i cant see any major issues with it, but i wouldnt want to leave it like that long term

 

[NozSpark]

If you've hit bedrock then you might be better off digging a trench and putting tape or a grid in?

 

[Theorysparky]

Apparently the spark working next door had the same issue a few months back,,went all round the house until he got a good reading....

will know more tomorrow......

 

[PC Electrics]

No option to get the DNO to provide a pme terminal??

 

[Theorysparky]

that may be a call to make tomorrow if the readings dont improve

dont think pme is available here,,its in the sticks

 

[hertzal]

thought the max reading was supposed to be 200 ohms to allow for changes in the reading due to the soil drying out or freezing etc.

Regards hz

 

[Andy™]

thought the max reading was supposed to be 200 ohms to allow for changes in the reading due to the soil drying out or freezing etc.Regards hz

the 200 ohms is not a max reading, but anything over should be classed as unstable. so you should be aiming for lower than 200 where possible

 

[PC Electrics]

I'm regularly working "in the sticks" in Harborough district. Even in the smallest villages pme seems the norm. Make the call.

 

[Revved Up Sparky]

Theory I had to deal with a very similar situation just before I left the Isle of Man last year. The Ra on the first rod was 800 ohms. I could'nt get any deeper than about 4 feet anywhere so I whacked in four additional rods in four different locations in the front garden (all spread apart by the recommended distance) and only then did I get a combined Ra of just less than 200 ohms. Thankfully I got the customer to dig all the trenches and lay all the conduit and 16mm earth !.... I was glad to get out of doing that bit !.

 

[Theorysparky]

my mate will dig the trenches if needed !!!!!

---------- Post Auto-Merged at 15:14 ---------- Previous post was made at 15:13 ----------

I'm regularly working "in the sticks" in Harborough district. Even in the smallest villages pme seems the norm. Make the call.

i did a new build in Hallaton

that had pme...

 

[steptoe]

Theory I had to deal with a very similar situation just before I left the Isle of Man last year. The Ra on the first rod was 800 ohms. I could'nt get any deeper than about 4 feet anywhere so I whacked in four additional rods in four different locations in the front garden (all spread apart by the recommended distance) and only then did I get a combined Ra of just less than 200 ohms. Thankfully I got the customer to dig all the trenches and lay all the conduit and 16mm earth !.... I was glad to get out of doing that bit !.

Pure slate rev, eh?

Done one in Laxey, 17rods later I got 87 ohms. you sometimes feel like its a losing battle!

 

[Revved Up Sparky]

Pure slate rev, eh? Done one in Laxey, 17rods later I got 87 ohms. you sometimes feel like its a losing battle!

Yes it was a house on a rocky hill in Maughold. Probably the hardest TT job I've ever done. I had one nearly as bad in St. Marks too- another house on a rocky hill ...

But 17 rods ........ wow now that is something

 

[steptoe]

Maughold! :slap

Your lucky you even got 4' deep there, a couple I done there we laid the rods in trenches.

Then again, I done one rod at Laxey laundry and got <100 ohms !

 

[Theorysparky]

went back to the job today and the customer had got the rod to ground level

tested it and got 320 ohms

packed the earth in further,,,,,,1 bucket of water 230 ohms that was 9 am

changed the board tested again 5.30 pm

209 ohms FFS

I have asked the customer to put another rod in.....

 

[steptoe]

Theory,

are you using decent rods? and not those things that are about as thick as a welding rod? :slap

 

[Theorysparky]

dunno the customer purchased it from Denmans.......

anyway hes putting another in hopefully get 199 ohms !!!!

 

[Sidewinder]

Theo,

How long are the rods, make sure that you space them by the combined length of the rods.

i.e. 2 x 4' rod at least 8' apart if you get 209 on the 2nd rod as well as the 1st individually, then hopefully you should get around 100 combined!

 

[Theorysparky]

I have told him where to put it its about 5m away so we will see

 

[Sidewinder]

5m should be great mate, that way you can double up the depth if you need to on both rods.

That will help,

Put one in last week got it down to about 36 ohms, 5/8" rod 2 deep.