No Earth from Supply on front of terraced house

[scouseneil]

Local electric company replaced all house feeds to the street. This runs above ground on the front of the terraced house. The outside has two cables running along the wall with joints outside each house. Inside each house (had a look at two others) the two cables run to a 100A fuse then to the meter. There is no earth supplied for the consumer unit. There is an earth block connected to the gas pipe and water pipe with 10mm earth wire. Have noticed tingling on some taps. can not remember if the supply company provided an earth before. Is it normal for a supply that comes in above ground from the front of terraced houses not to have an earth provided. Thanks

 

[ColJack]

photo's of cables and service heads would be good..

 

[kkynaston]

The supply to my mid terrace is exactly the same, recently replaced.
At the end of the terrace though it terminates into a lucy box and then goes underground and up a pole on the otherside of the road to join the overhead cables.

The supply is PME although I know a couple of houses are still TT

 

[securespark]

It is very common for TT supplies (those without an earth connection supplied by the DNO) to be replaced like for like. If your supply was TT, then the DNO have no obligation to provide an earth terminal, however, see the bottom of my post.

As said before, I have seen TT supplies fed off a TN-S main feed on the end terrace, fed into each house as TT.

In Staffordshire, MEB is replacing TT supplies with PME, leaving each house as a TT supply. The householders can apply for PME if they wish.

The tingling is because your supply and pipework do not have an adequate earth connection.

I am guessing your water and gas come into the house on polypipe, not metallic ones?

You need either PME or a rod & RCD's installed.

Talk to the DNO guys (if they are still around) about PME, if it's available. Ply him with fags, coffee, biccys etc... Maybe he'll take pity on you.

 

[scouseneil]

will take a picture in the morning. The road is split in two , each half fed from a metal box. The house is over 100 years old and mid terraced. The earth block next to the CU is connected to both the Gas and Water. Over the years I think we have lost our earth due to metal mains pipes being replaced by both Gas and Water companies. Hot, cold and Gas are all cross bonded and connected to the earth block by the CU. Time to put a few earth rods in I think. As the CU is in the living room I do not fancy a rod there. Is there a limit to how far away from the CU the rod can be. Is 10mm cable enough or should I go for 16mm. Thanks for all your time.

 

[securespark]

will take a picture in the morning. The road is split in two , each half fed from a metal box. The house is over 100 years old and mid terraced. The earth block next to the CU is connected to both the Gas and Water. Over the years I think we have lost our earth due to metal mains pipes being replaced by both Gas and Water companies. Hot, cold and Gas are all cross bonded and connected to the earth block by the CU. Time to put a few earth rods in I think. As the CU is in the living room I do not fancy a rod there. Is there a limit to how far away from the CU the rod can be. Is 10mm cable enough or should I go for 16mm. Thanks for all your time.

Best not to put a rod in internally. You need good contact with solid wet ground to give a reading of no more than 200 Ohms in the least favourable conditions.

You may well have had an earth originally from the water pipe, but this was deleted from the regs in 1966. You most certainly cannot rely on the earth connection from the water pipe now, nor from the gas pipe.

As for the size, it need not be larger than 6mm² to comply but thee's no harm in using larger sizes. You must use 30mA RCD protection for all circuits, hence there is no need for a huge csa for the main earthing conductor.

BUT, my best advice would be to get PME if you can. Sinking a rod can be a PITA.

 

[scouseneil]

Being in a terraced house we have no outside to talk of, only at the rear of the house and then it is very small. Can not see the local supplier wanting to give us a PME, we are in the middle of a terrace. Any idea of what they charge to supply a PME. Here is a picture of how the wires arrive in the house. You can see on the top the original wires still in the render of one house. I guess that it is about 15m from the CU to the rear of the house where I could try some earth rods. Looking down the street it looks like a neigbour has put a rod in the front just as the house joins the sidewalk and buried it, can just see the wire. I've also posted a picture of the main fuse. The supplier replaced the original ceramic fuses with this and connected the meter tails to the top. It would look like the supplier has never supplied an earth and the house has always relied on the water and gas, now poly.
Thanks for all your thoughts.
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[Steve]

As its a concentric feed they may give you PME. Ask nicely.

Have you asked your neighbours if their earth rod is still in use?

Did you ask the engineers while they were there, what the earthing arrangements are?

Urban areas are more likely to be able to get PME due to their proximity to large substations (rural areas use small subbys because they only supply a few homes, therefore the cost of upgrading the subby to a PME-compatible one etc is more)

And whats with painting the cables? YEDL wouldn't do that

 

[scouseneil]

By chance on of the neighbours mentioned today that he has been getting the same problems. The cables was done a few years back and all was well, (never gave the earth a second thought) but over the last few years we had both Gas and Water put in poly, hence the problem. I have now added a single earth rod, added extra cross bonding between water pipes. Just checked the loop impedance on a digital loop tester, the type that plugs in a ring main socket. Before it was off the scale and would not read, it is now 18 ohms. I guess there is no harm in adding a further rod for good measure. How low should I get it on a TT system. Thanks again.

 

[ColJack]

less than 100 ohms...

 

[scouseneil]

Thanks everyone who has helped. feel a bit safer about the house now !

 

[scotsparky]

Hi Scouse

The electrical supply authority are not obliged as jet to supply an earth however as a lot of people are checking earths and complaining about TT systems and having to put in RCDs and RCBOs installed the oversight commity are about to say all new installations have to get an earth supplied. Talk to them and you may get your system changed to a TN-C-S system (PME) it involves an earth block being installed and a 16mm earth Being linked to your incomming netral conductor it only takes about 15 mins to do.
If you have to put in an earth rod use a 16mm earth cable as a link its the minimum size allowed for a main earthing conductor (BS7671-2008)
The other way to go ( If yor lucky) is have a good look at the cable head and if there is a terminal for an earth then the supply authority have mis represented the supply provided and will have to provide an earthing arrangement.

 

[aptsys]

If you have to put in an earth rod use a 16mm earth cable as a link its the minimum size allowed for a main earthing conductor (BS7671-2008)

Are you sure?

 

[scotsparky]

Yes BS 7671-2008 (17th edition ) chapter 54 Table 54.1. Normally a main earthing conductor is unprotected. Besides which the rule of thumb is Half the size of the main Incomming phase conductor. Which to the main D.B will be a 25mm then half that is 12.5 you cant go gown a size so go up to 16mm

 

[ElectricDunc]

Just to add my pennys worth. If your fitting an earth stake it would be prudent to put in 16mm as has already being stated. The earth stake requires an enclosure to protect the connection from the elements if fitted outside to ensure a good connection is maintained. A 100mA RCD should then be fitted to the feed before it gets to your consumer unit. This will hopefully give you less problems with nuisance tripping. If you have a 17th Edition consumer unit the 100mA RCD isn't required as all your circuits will have 30mA protection but if you have no 30mA protection i would consider upgrading your consumer unit. The last thing to do is confirm that the loop reading on the earth stake is less then 200ohms. Ensure that your only testing the earth stake though as you could end up with false readings due to parallel paths through gas and water pipes. Either that or give the supply authority a call and get them to fit a PME terminal. Will usually cost £75+VAT which is a joke considering they usually just drill 4 holes in the cutout to access the connections. Hope that helps.