No earth - is it a TT looks like PME to me

[leolec]

Just want to bounch this off others,

1980's house built in rural village, other houses in the village have PME supplies and test out with Ze of around 3.5. Did a quick test when I got there on a ring and getting Zs of 10.45 on further investigation theres no main earth so thought well is this TT if so no rod - can't be - main incomer comes out of the ground looks just like other PME supplies light grey 100A fuse box SWA going in - did the installer just miss the earth off? seems strange - 10mm Main Bonding all there.

 

[leolec]

yes that is a series 7 the neutral terminal block cover on the right of the fuse has on its right hand side some round drill guides. this correspond with a knockout hole on the top right edge next to the neutral tail ideally you want one of these INSULATED 3MM ALLEN KEY T-HANDLE 40MM OAL

Again I have to add (I accept no responsibility if you drill/knockout the wrong part)

Ok - I saw the drill guides so I'm comfortable with that.

Will there be any side effects - they have a 16th ed board with one 30ma RCD as the main isolator, will improving the earth lead to nuisense tripping, or should it make the system more stable?

 

[mechelec]

no additional tripping problems all you will get is a more reliable earth. The RCD in the board should not be affected by anything on the supply side.

 

[keniff]

i know you have solved this one, but in the area im working we always find houses in the countryside with no setup on the earth. just an earth going to the water and using the water pipe as a earth rod!!

 

[nickblake]

Best ever reading i have got on a TT install was 0.98 and that was with all the bonding removed too

 

[keniff]

Best ever reading i have got on a TT install was 0.98 and that was with all the bonding removed too

i wonder how much that mile long earth rod cost lol

 

[nickblake]

they probabley hammered it through the neutral of an under ground cable !! lol the rod looked like it had been there for years and the old chap in the house had painted it green and yellow too , but well good readings

 

[sjm]

Is the DNO cable hybrid ie concentric construction and is the cutout is a modern grey series 7 with a cover on the left hand side for the neutral terminals and earth? if so there are some drill out points on that cover for access to the 3mm grub screws to enable you to knock out the hole in the top to insert your 16mm earth all without removing any seals. BUT before you do this do a loop test between the neutral and phase of the incoming supply with main switch off. If it is below 0.35 ohms you can assume it is OK to PME and insert your earth. This is all the DNO will do if they come round. Be very careful if you are unsure what should be drilled out, leave it well alone and get the DNO in. ( I accept no responsibility if you drill/knockout the wrong part)

The ONLY people who can supply an earth connection on the cut out fuse are the DNO.
Do not assume you can connect an earth even if loop test under 0.35 ohms.
Do the correct thing and make PME enquiry to DNO then if they agree you can have an earth connection pay them the money to do it. Western Power charge £40.43 inc vat or £95 if a new cut out fuse is required.

 

[leolec]

Thanks everyone for the advice, I'm going to leave it with the DNO.

I let you know what the outcome is.

Many Thanks

 

[mechelec]

The ONLY people who can supply an earth connection on the cut out fuse are the DNO.
Do not assume you can connect an earth even if loop test under 0.35 ohms.
Do the correct thing and make PME enquiry to DNO then if they agree you can have an earth connection pay them the money to do it. Western Power charge £40.43 inc vat or £95 if a new cut out fuse is required.

May depend on the DNO in your area. The whole point of the drill markers on the cutout is that the DNO is supposed to drill them out to allow the electrician to connect their earth to. it is usually done in my area when the supply is connected to a new property. And never connect an earth to the cutout fuse as this will be live it is the neutral that the earth is connected to. The DNO will not do this!!!!!!!!!!!

 

[sjm]

The cut out fuse unit takes the phase and neutral lines into it and has a fuse in the phase line. The neutral line has a link across to the earth connection if PME is available. As I posted the ONLY people who can make PME available are the DNO. I have had 3 occasions when a loop test has been under 0.35 ohms but the DNO have not made PME available.
I assumed it was obvious that I was talking about the cut out fuse unit which contains the earth connection and not saying to connect the earth to the phase line! That would just be plain stupid!!!!!!!!!!!!!!!!

 

[aptsys]

Is the DNO cable hybrid ie concentric construction and is the cutout is a modern grey series 7 with a cover on the left hand side for the neutral terminals and earth? if so there are some drill out points on that cover for access to the 3mm grub screws to enable you to knock out the hole in the top to insert your 16mm earth all without removing any seals. BUT before you do this do a loop test between the neutral and phase of the incoming supply with main switch off. If it is below 0.35 ohms you can assume it is OK to PME and insert your earth. This is all the DNO will do if they come round. Be very careful if you are unsure what should be drilled out, leave it well alone and get the DNO in. ( I accept no responsibility if you drill/knockout the wrong part)

I really hope that you have never done this before as is really bad advice to post on a public forum. The DNO will make an earth terminal available if PME is available. If a terminal is not available and there is no sticker on the head indicating that it is a PME supply then you should not just go ahead and find a way of DIY'ing it. It may be that the network isn't earthed at regular points or unadvisable for a whole host of other reasons. A low loop test result is only half of the story!

 

[Leshark]

Hi, just had a new supply in and the DNO just told me over the phone to knock out the tab and to tighten the grub screw on the earth, but I wanted to be sure where the tab is and where to drill/knock out, does anyone have a photo with a simple arrow on it?

 

[Sparky.]

If its a hybrid supply cable coming in and there is no seperate earth wire then its prob pme. If its a new supply fitted then it should have the loop reading on the crutch cover or a PME Sticker.. either and its pme. The dno should have knocked out the hole for the earth but they do not always . what colour is the service head.

 

[trev]

The DNO have given you authorisation to play with their toys? If I were you I wouldn't mate, not without it in writing and I've got 30 years experience under my belt.

 

[Leshark]

Hi, just had a new supply in and the DNO just told me over the phone to knock out the tab and to tighten the grub screw on the earth, but I wanted to be sure where the tab is and where to drill/knock out, does anyone have a photo with a simple arrow on it?

grey, it sort of says, but i just want to be certain, on the plate that sits under the master fuse, "remove when module is on right hand side" im prety sure this s where the grub screws are then i believe the earth goes in the top