Tt system

[Blueblood]

HI, I am an industrial maintenance electrician. A friend who does not live in my area has asked me a question can anyone please advise. He has had an electrician replace his consumer unit. It is a TT system. The electrician has installed the earth rod under the floorboards by the new consumer unit and there is no RCD fitted to the supply. He has not recieved the test cert. yet so I don't know what the readings are. I am going down to see him next week so I wanted to make sure I have all the correct information. Am I correct in thinking that as the supply has no RCD the rod should be measured with an earth electrode resistant tester and 2 test spikes and looking for a reading less than 200OHMs. Ideally I think an RCD shoul be installed, can you advise what size.

Cheers

 

[m4tty]

Tt must be covered by rcd. All socket outlets have to be rcd protected under 32a. Hth

 

[acat]

The person who did this job must also be registered with a competent person scheme ie NICEIC NAPIT or ELECSA. If he is not building control had to be informed before work commenced if it was not considered an emergency and if an emergency building control has to be advised as soon as possible.

If he is a member of one of the above schemes you must put your complaint in writing to him and give him time to rectify. Should he fail to do so then complain to his scheme provider enclosing a copy of the original letter to him.

If not a member then trading standards is the next port of call.

Best of luck


Chris

 

[Blueblood]

Hi. Thanks for your reply. I have contacted my mate and he tells me that the sockets are protected with a 30mA RCD. He is more concerned with the fact that the earthrode has been installed under the floorboards and that there is no RCD fitted to the supply. Please can you advise, so that I can check it out for him when I get there. Cheers

 

[Risteard]

Tt must be covered by rcd.

Technically it is not required. However it is highly unlikely that disconnection times can be met without the installation of an RCD.

In theory though if the impedance allowed then an RCD would not be required.

 

[Deleted member 9648]

Ideally you would be looking for either a split load board with a 100ma rcd main switch protecting all circuits and a 30ma rcd protecting sockets/bathroom circuits etc.
Or a 17th board with a main switch and 2 or more 30ma rcd's....or a board with a main switch and RCBO's on all circuits.All final circuits should be rcd protected in practice.
The DB should be all insulated as well.
The rod measurement should be below 200 ohms....and main bonding to incoming services must be present....minimum 6.0mm.

 

[Blueblood]

Cheers Wirepuller.
Have been doing some researh myself. I totally agree with what you are saying. Thanks again

 

[Sintra]

No need to fit RCD to supply unless supply enters a metal clad consumer unit.
All outgoing circuits should however have appropriate RCD protection.

A single RCD protecting a TT system must be installed at the origin of the installation unless the part of the system between the origin and the RCD fulfills the requirements for protection by Class II equipment or equivalent insulation. 531.4.1

As for the earth rod

All electrical equipment must be accessible for operation, inspection & testing, maintenance and repair. 132.12

 

[havoone]

ive never come across an electrode within a building they always are outdoors, though i cant see anywhere in the regs it states that you cant. however wouldnt it be good practice to install outdoors especially if theres a good chance of the usual building materials such as stone etc being under the floor and creating a high resistance to earth? weve always been taught to install outdoors.

 

[Spudnik]

Ill stick my nose in here as i normally do

TT installations no longer need a 100mA TD RCD upfront of the cu, as all circuits now should be protected via 2 30mA RCD's, and provided it is all in an insulated consumer unit.

I cannot see any reason why an earth rod cannot be installed under the floor below the Cu PROVIDED it is accessible and labels and cert marked with the location (there is a box on the cert for this anyways).