Consumer unit upgrade TT system

[monkeyhanger]

Appreciate a bit of advice regarding this that I'm doing in the morning-

Consumer unit upgrade in house with 6mm gas & water bonding existing (leaving bonding as it is). Existing rod in house with 6mm up to CU.

(Existing install) From a TT system in the house there is a 2.5/1.0 T&E running to a detached outhouse (perhaps, four meters from the back of the house) feeding an existing fuseboard in there with BS3036 fuses for 15A sockets radial and 5A one light.

The outhouse has a copper water pipe supplying a washing machine. This isn't bonded where it rises from the concrete floor in the outbuilding and there isn't a seperate rod in there. The only earthing of anything in there is the 1.0mm CPC of the T&E submain & CPCs of light/sockets.

Am I right in thinking that the CPC in the T&E won't suffice in the requirements for equipotential bonding in the outbuilding (it appears that the T&E is ran under the concrete back yard in plastic conduit.. many years ago). If I install a rod & earth conductor to the existing BS3036 unit in the outbuilding and bonding between this unit & the copper pipework in the outbuilding, should I insulate the 1.0mm CPC in the T&E submain from the outbuilding installation (at the outbuilding end)? Or leave it connected at both ends- in the house and the outbuilding. If either is acceptable would it be best practice to leave it connected both ends?

I am quite aware of requirements when exporting TNS and TNCS but I've never came across TT in the main building with an outbuilding where bonding is required.

This is hopefully obvious to one of you who may read this before tomorrow

 

[davesparks]

Frigging hell Dave, we're not in the Arctic Tundra!

I don't know where he is, it could easily be the frozen north. They have icebergs and polar bears everywhere north of Watford don't they?

 

[PEG]

I don't know where he is, it could easily be the frozen north. They have icebergs and polar bears everywhere north of Watford don't they?

...The day before yesterday,i was running back and forth,outdoors,taking readings with an AC/DC clamp ammeter,alternating between loads,(see what i did,there...)...and get thrashed with the hail storm...

...Me tee-shirt was soaked :joker:

 

[Engineer54]

Frigging hell Dave, we're not in the Arctic Tundra!

The ground doesn't have to be frozen for the whole 4' to make a considerable difference to the Ra value, which is why stability over the seasons is an important factor in any TT system....

 

[monkeyhanger]

Afternoon everyone, just to update the thread with regards to the job to help anyone who reads this in the future in a similar situation. I installed a 4ft rod to the outbuilding, 80 Ohms. Bonded the water. Phoned NAPIT technical support who advised me that it was acceptable to leave the CPC in the submain T&E connected, however if I wished I could disconnect it. I left it connected.

I left the existing rod in the house as I found it, tested & reconnected it to the earth bar in the new CU.

Now lets not have any bickering, enjoy the bank holiday weekend!

 

[monkeyhanger]

Incidentally, personally, if it was above about 80 ohms I would have coupled another rod on

 

[trev]

Why is 80 ohms the magic figure? So 81 you'd have drove another but 80 is tickety boo

 

[monkeyhanger]

I'm not sure why, just a preference!

 

[Knobhead]

My preference would be <1Ω

So where does 80Ω come from?
Would it be that it just happens to be 80Ω on this installation and you can grab the money and run without any real work?

 

[trev]

My preference is also for <1 ohm. I've done it dozens of times, my record is still the same. I've not beaten 0.29 yet. Did one last week and got 0.58 which I was pretty happy with.

 

[Deleted member 9648]

Incidentally, personally, if it was above about 80 ohms I would have coupled another rod on

Why is 80 ohms the magic figure? So 81 you'd have drove another but 80 is tickety boo

I'm not sure why, just a preference!

Priceless!

 

[Silly Sausage]

My preference is also for <1 ohm. I've done it dozens of times, my record is still the same. I've not beaten 0.29 yet. Did one last week and got 0.58 which I was pretty happy with.

You've got the rare knack of hitting underground cables Trev!

 

[trev]

And water supplies and sewerage pipes mate

 

[richy3333]

And water supplies and sewerage pipes mate

And I'm guessing Australia to get a reading that low.

 

[trev]

And I'm guessing Australia to get a reading that low.

Nah. Big, fat rods and cables mate

 

[Leesparkykent]

Chill out mate, earth rods have always been a touchy subject on here lol. ^^