no earth rod in tt system

[meady]

I have just inspected an tt installation which the client wants a cu upgrade. The house was built in the 1960's so I thought the installation should have all the essential parts already in place. After a closer look I discovered there is no earthing system present. My problem is the meter and cu is smack in the middle of the house so it will be very awkward to route a 16mm earth out to the nearest point I can install the rod.

I have heard of some suppliers turning a tt system into a tn-s sytem. This would be ideal for this situation but who pays for it? does the supplier front the bill or the owner of the property?

Also what size meter tails should be supplied?

 

[green-hornet]

Have you done any tests to establish if there is an earth?

It could be very easy to assume there is none but find later that there is one.

The earth rods are normally installed outside the property because of the general ground works.However there is nothing in the regulations that would prevent an internal installation, providing the earth rod is tested and is as good a connection to earth as could be expected outside the property.

One of the reasons for a TT installation is because the DNO will not except reponsibility for a poor earth, so it would be un likely that they would now take responsibility.

I would check the supply for any damage that may have been caused by previous works "cough" electricians, and any cut earth cables that have not been reinstated.

 

[Andy™]

you can often take up a floorboard under the mains cupboard and hammer in rod there. but make sure you know exactly which way the main feed goes! (its normally resting on ground, so no problems there)

upgrading from TT to TNCS may be possible

there is also the fact one may already be installed, but not visable. any earths leaving the board heading to an unknown destination? you also dont always need 16mm

 

[meady]

Not done any tests but I inspected the 2 fuse box's and there is no main earthing at all. All the cpc's from each circuit coming into the fuse box just connect to the external metal fuse box unit, there is no earth bars or anything. I have not long been in this game and this is my first tt system I have seen due to me working in a busy built up area. I have walked around the outside of the property with the owner and there is no sign at all of the rod location. Is it a common situation to find there is no earth rod's in tt systems?

 

[Andy™]

many older properties relied on the water for the main earth

 

[meady]

yeah i checked the gas and water for the earthing, guess what!! there was no bonding to either of them lol, from what I can see there is no earthing at all in the property

 

[paul b b]

Hi Meady,

as i have found out a lot of suppliers (edf etc) want a 16mm2 earth so best to upgrade it.

also its best, if possible not to take up a floor board in the meter cupboard as the earth needs a good bit of damp ground to get a decent reading! (as i found out at home).

I have been to a few myself and told the client the only option is to take upstairs floorbords and run to the back of the house.

I also ran the earth in conduit down the wall into a black box with warning lable on.

hope this helps

 

[paul b b]

yeah i checked the gas and water for the earthing, guess what!! there was no bonding to either of them lol, from what I can see there is no earthing at all in the property

like loads of houses in my village, as soon as i have had my assessment i'm sending out flyers!!

 

[Andy™]

yeah i checked the gas and water for the earthing, guess what!! there was no bonding to either of them lol, from what I can see there is no earthing at all in the property

done many DB changes on older properties where all earthing for sockets/lights etc is connected to the fuse box earth terminal... problem being, this isnt connected to an earth!

 

[meady]

Sounds like my only option is to install an earth rod at the back of the property, run a 16mm cable and then bond the gas and water, damn these tt systems!!.

Am I right in saying the min size of the the water and gas bonding is 6mm?

 

[Andy™]

yes, although its often easier to install 10 and be future proof (and i dont carry 6mm

 

[green-hornet]

Hi Meady,also its best, if possible not to take up a floor board in the meter cupboard as the earth needs a good bit of damp ground to get a decent reading! (as i found out at home).

hope this helps

This is never good practice, but I know people use to do this intentionally to get a good reading for the certificates.

Problem being the potential danger when the ground is dry, and unstable earthing results.

 

[Andy™]

every rod ive installed indoors has always had a decent reading (less than 100). but its often only a few metres to 'outside'

 

[Evans Electric]

Hi Meady, may I suggest buying a drum of 10mm G/Yell for future use. Use for bonding and rod. In the sixties it was rare for testing and certifying to be done . You have two options on that job , a rod or request an earth conection from the network.

Deke

 

[Andy™]

And with part p etc, its even rarer now to get a I&T and certs!

 

[meady]

Cheers fellas, im going to install a rod as close as I can to the meter but I fear this will be at the rear of the house due to solid concrete foundations. I estimate the run I might have to install will be about 6 - 10 meters. Would that be sufficient or should I try to get it a bit closer?

 

[Andy™]

6-10mtr should be fine. even double that wouldnt really be a problem

 

[meady]

Ok well thats the plan then, thanks for your help fellas. Learnt alot about tt systems tonight (not to take on the job) lol

 

[Evans Electric]

Are you jesting or really not going to do it? Can you afford to turn work away, or don't they wish to pay for it ?

 

[meady]

Just jesting mate, times are hard and need all the work i can get. Its my first time on a tt system and so far it seem a right pain but at the end of the day these jobs pays the bills and its good practise for me aswell. learnt alot tonight and will learn alot more once im stuck into it