TT systems and cu set ups

[eds_taff]

I have read in a different thread that if you have a TT system then you need to have a cu with a time delay 100mA RCD feeding everything, and then a 30mA RCD for all the power circuits etc. (have I got it right?)I have recently been looking at my house electrics (something I should have done before I moved in I know) and I have a TT system but with a split load cu with double pole 100A main switch. I also do not have any bonding on pipework etc. that I can see anyway. Is this required with a TT system?

I do have a 16th ed regs book, but at the moment I cannot find it.
Any help or any good web links on this matter would be appreciated, I really need to find out if everything is safe, and if not, what I need to do to make it safe.

Cheers

 

[davy_owen_88]

Main equipotential bonding is a requirement regardless of earthing arrangement. It's run in 10mm^2. to the main earthing terminal in your consumer unit.

Heres a useful link: http://www.tlc-direct.co.uk/Book/1.1.htm

And relating to your post:

http://www.tlc-direct.co.uk/Book/5.4.3.htm
http://www.niceic.org.uk/downloads/Earthing Bonding guide.pdf

Davy

 

[securespark]

Yes! You need MEB's & supplementary in the bathroom.

You also should have RCD-protection to give rapid disconnection times, as your TT Ze will most probably be too high to achieve this without.

I would fit a split-load board with 100mA S type RCD where your incomer is, or others here have a different solution. Calling John!!

Another option, which means you can stick with the board you've got, is to ask your DNO to give you a TN-C-S (or PME) connection.

But either way, you def need MEB's & supplementary, if you have nothing ATM.

 

[eds_taff]

Thanks for the swift replies lads.

I think I will go for the 100mA RCD, is it a straight swap for the double pole main switch? By this I mean does anything else need changing on the board? And I will get the MEB and the supplementory bonding sorted asap.

 

[Taylortwocities]

It should be a straight swop. Make sure its a time delayed one and get one the same make as your existing main switch - some busbars are offset and you may have problem if you get a different make...

You will, of course be testing the RCD once its installed? An RCD tester is needed for that.

TTC

 

[Taylortwocities]

It should be a straight swop. Make sure its a time delayed one and get one the same make as your existing main switch - some busbars are offset and you may have problem if you get a different make...

You will, of course be testing the RCD once its installed? An RCD tester is needed for that.

TTC

 

[RF Lighting]

Make sure it is time delayed to provide discrimination between the 30mS and the 100mS RCDs

 

[securespark]

 

[fastJedi]

If you can't get one to fit in the CU you can fit one in a separate enclosure between the meter and the CU.

If you decide to change your CU make sure you can get a suitable RCD for it (Not all manufacturers supply them)

 

[eds_taff]

Yeh I think I will have to get one in a separate enclosure as my cu is a Legrand(Tenby?), and I am having trouble finding an RCD of the same make.
I am not sure what my incoming fuse is but am I right in saying I need an RCD rated at 100A?
And yes I will be testing the RCD after installation

 

[Taylortwocities]

Make sure it is time delayed to provide discrimination between the 30mS and the 100mS RCDs

The 100mA RCD must be an S type (Time delayed)

TTC

 

[securespark]

And the 30mA a G type...

 

[ample]

Also if your board is metal, the tails will need to enter through a non-metallic opening.

 

[securespark]

Also if your board is metal, the tails will need to enter through a non-metallic opening.

 

[RF Lighting]

Shouldn't that be the CU must be insulated (not metal clad) if the tails are not RCD protected?