pro's advice needed

[daiplayer]

Working in a house , have already rewired the kitchen , have been ok'd to rewire first floor lighting .( due to poor condition)

Am trying to keep costs down for customer when bringing house wiring up to standard.

Will be doing some more remedial works but am trying to suss out whether they need bonding upgrade.

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 ?

 

[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!!

 

[malcolmsanford]

May have had the earth conductor still removed for the Ze test and may not have reconnected it to do the PEFC .....................done that myself a couple of time..............................oopps

 

[Rockingit]

Malcolm - let's face it; either which way, it's not going to be you or me out with the sledge hammer knocking rods in. Fancy a beer that day whilst we watch?

 

[malcolmsanford]

You know what mate I have yet to put a rod in with an SDS ...........................it's still hit and hope with me, luckily or hopefully more like, I want my days of fitting rods to be of a minimum now, but never say never ...............fancy some scratchings with that beer ???

 

[daiplayer]

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.

Sorry my typo : r1+r2 of 3.35. lol

think im gunna just put longer rod in . yes they are covered by rcd od course ( dis times etc) just trying to keep costs down for customer ( single mum ). doing this will enable the continued use us existing bonding . therefore wont hav to ripp up her laminate flooring to run new 10mm.

Conversion to PME will mean upgrading , therefore cost and damaged flooring.

 

[Rockingit]

.it's still hit and hope with me, luckily or hopefully more like, I want my days of fitting rods to be of a minimum now, but never say never ...............fancy some scratchings with that beer ???

Not an earth rod, but a couple of summers ago I was on a festival site and there was a problem with one of the tent pins (metal stakes) on a massive tent/stage... the pin HAD to be where it was, but had hit rock - the problem being that if you dug the rock up there'd not be enough friction left afterwards for the pin. A JCB came along with one of those hydraulic thumper things on the arm, but after 10 mins the driver gave up and disappeared......so for 2 whole days a site team of fit strong lads (and a couple of lasses) took it in turns just to whack this thing with 18 pound sledges - and a fraction of a mil at a time, it eventually went in.

 

[Engineer54]

Re adding a rod: If you go that route it will need to be at a distance away at least 3 times the length of the existing rod

Where on earth did you get that from?? You'll be seeing very little advantage, spacing more than 1.5 to 2 times max, the driven length of the first or existing rod....

By linking to a Yank web page perhaps more importantly to note the size/length of ''THERE'' standard earth rods, smallest being 8 foot, but generally 10 foot!!!! Bit different to the thin 3/8'' 1m twigs that i keep getting told are suitable for purpose!! Like hell they are!! ...lol!!

 

[Engineer54]

Sorry my typo : r1+r2 of 3.35. lol

think im gunna just put longer rod in . yes they are covered by rcd od course ( dis times etc) just trying to keep costs down for customer ( single mum ). doing this will enable the continued use us existing bonding . therefore wont hav to ripp up her laminate flooring to run new 10mm.

Conversion to PME will mean upgrading , therefore cost and damaged flooring.

So the families safety and well being, is secondary to your customer, than the thought of disturbing a laminate floor?? And what's worse , you seem to agree with them!!!