Tt board change

[paul b b]

Try another rod either 2 screwed together (Furze) to get deeper OR another Rod in Parallel, just make sure you sink it at least rod length distance away, this will often half resistence, if not then 396ohms will still comply with Regs, 200 ohm ONLY RECOMMENDATION as ideal see BRB Pg 50, 1666.66 max.

is it not 1.5 times the depth? i normaly put them 2x though

 

[paul b b]

Just put the CU in. Tested Ze by disconnecting electrode cable and connecting from incoming feed to main switch. Got 396 ohms. Checked again after 3 hours rain - 395 ohms so looks like new earth rod and 16mm cable is in order. GHouse wiring a problem as there is a break in the ring. I suspect kitchen fitter who installed new sockets last year. Have put 2 legs on 16A MCBs for now.

just be a bit carefull, what will hapen when your not there and the ground is dry??????

i have a TT and whist away training to become a spark my wife had a shock (how ironic is that) i had not touched anythin and the has was rewird by a spark 5 years ago, all bondings in place etc... i told her to get someone in and he tracked it down to Ze being 356 ohms, replaced rod and all sorted (the existing rod was under a floor and dry as a bone) so im overcausious with rods and like them to be 100 max on a dry day

 

[m4tty]

http://www.screwfix.com/prods/32831/Electrical-Supplies/Consumer-Units/Wylex-Consumer-Units/Wylex-10-Way-High-Integrity-CSU?ts=24349

That board will be ok wont it?

Anyone got any feedback on this board please?

Cheers

 

[NozSpark]

So long as all circuits have RCD protection then it'll be ok..

This is my latest TT CU

 

[revjames]

Just an update on this one. I'm down in the south west on holiday again. Just put a new earth rod in. I left the original one in with the 6mm cable going back to the MET. I installed the rod and wired it in a 16mm cable in a flexible conduit down to a purpose made box in the ground. Tested and its now 132 ohms. Happy days.

 

[Lee321]

nice one rev. what rcd arrangements?

 

[revjames]

there is a very old one between the cut out and meter, unsure of rating. New Wyles board with 2 x 30ma RCDs covering all circuits.

 

[batty]

there is a very old one between the cut out and meter, unsure of rating. New Wyles board with 2 x 30ma RCDs covering all circuits.

Surely it's between meter and consumer unit?

 

[Chr!s]

16mm g/y only required if the cable is to be burried. If earth box is above ground then use 4mm.

See page 29 OSG!

Lets not pull figures out of anywhere, Table 54.1 are minimum sizes for buried earthing conductors.

2.5 and 4 mm are minimum sizes which are relevent to reg 543.1.1 (iii), (iv), (v).

reg 543.1.1 requires us two use two methods,

The adiabatic, or table54.7

If the installation is tt how are you going to calculate using the adiabatic?

So more than likely we will need to use table 54.7 to size the earthing conductor.

What method are you using to calculate the circuit cpcs for compliance?

regards chris

 

[batty]

16mm g/y only required if the cable is to be burried. If earth box is above ground then use 4mm. See page 29 OSG!

Lets not pull figures out of anywhere, Table 54.1 are minimum sizes for buried earthing conductors.

2.5 and 4 mm are minimum sizes which are relevent to reg 543.1.1 (iii), (iv), (v).

reg 543.1.1 requires us two use two methods,

The adiabatic, or table54.7

If the installation is tt how are you going to calculate using the adiabatic?

So more than likely we will need to use table 54.7 to size the earthing conductor.

What method are you using to calculate the circuit cpcs for compliance?

regards chris

Hang on it maybe DNO require a 16mm main earth.

 

[Chr!s]

batty

Hang on it maybe DNO require a 16mm main earth

They may i agree,but im pointing out that people are suggesting sizes without due consideration, if the supplier leaves it to the installer to fit the correct sized earthing conductor then bs7671 gives us the methods

regards chris

 

[mikep]

All us guy's in London are inexperieced with TT I' have done just one so when I get another I'll probably have to ask to make sure again about doing it right.

Picture of my Rod box ( dosen't sound right that )

 

[Evans Electric]

As with other posters ,I am not happy doing TT, s I'm more used to commercial supplies where there is always an network earth terminal.

However there are some big areas of Birmingham where the network's joint boxes are breaking down and what were cable sheath earths (TNS) now have poor Ze readings.

You can never get an upgrade so TT is becoming more common.

Its amazing how many recent rewires I see with the Main Earth connected to a corroded clip on the lead sheath and a carp Ze .

 

[Apache]

All us guy's in London are inexperieced with TT I' have done just one so when I get another I'll probably have to ask to make sure again about doing it right.Picture of my Rod box ( dosen't sound right that )

Did you pee on it? It looks like you did!

:|

 

[revjames]

Sorry for the delay in posting further replies BUT yesterday was a scorcher and there was surf at Saunton sands beach so was there most of the day and it was awesome!

Back to the TT

Yes quite right, the old looking ELCB device (marked 60A 500V) and had a yellow test button but no ma rating shown, was inbetween meter and CU

I installed 16mm as I was told by another spark that DNO like to see 16mm on these type of arrangement. Also I think its less likely to get damaged, fall off etc.

Didnt see the need to do the adiabatic equation!

 

[sparkytim]

That old ELCB is probably a Voltage operated type, does it have an earth wire going in to F terminal and one coming out from the E terminal?

If so then it would be best to remove these earth wires as it could still trip in certain circumstances.

As you have 2 new RCDS in your new CU it is not required, but will do no harm to leave in as a Main switch.