domestic earthing

[whittledr]

Currently in a TT earthed property. The supplier refused to connect to incoming as its too close to the ground to physically fit.
TT has always given good readings to not cause any issue.
It has been mentioned to me by a qualified HV spark that I could simply tag my main earth terminal to the neutral of the intake to create a PEN. While I understand that would 'work' is it a good idea?
I know he knows what he is talking about but I am often doubtful of his advise in general!

 

[Strima]

It has been mentioned to me by a qualified HV spark that I could simply tag my main earth terminal to the neutral of the intake to create a PEN

Only the DNO can do this as the have to be certain conditions met to ensure the neutral is suitable to be connected to earth.

 

[DPG]

You cant just create your own PME connection. The DNO need to make sure the supply network is suitable for it, and only then will they make the conversion.

When you say they refuse to connect, has this property not had a supply connected before?

 

[DPG]

Think we typed that at same time Strima!

 

[whittledr]

When you say they refuse to connect, has this property not had a supply connected before?

The supply was in the building in 1933, when I moved in I asked for an earth and told it wasn't possible to achieve.

 

[DPG]

The supply was in the building in 1933, when I moved in I asked for an earth and told it wasn't possible to achieve.

I see, thanks.

 

[Marvo]

Don't do it. Under certain supply fault conditions a home-made TNCS that's not PME'd at several points upstream as well could cause a very large current to flow through your earth spike and in turn cause high touch-voltages on the chassis of your appliances.

You say your existing TT has a good 'reading', what does your earth impedance measure in ohms?

 

[Strima]

Think we typed that at same time Strima!

Great minds and all that... ?

 

[MJPD29]

Absolutely not. Do not create your own pme.

 

[justeez81]

Hi.

It is possible for the DNO to connect a TN-C-S system however it would depend on how the main is connected and earthed along route back to the substation. Back in theb30s the DNO never provided an earth or guaranteed one. Now a days they do with minimum ELI requirements for each. If you ring your DNO they can assist you with some information on the type of main (pilc or XLPE) and give you a price for a cut-out change along with a PME connection. I5 is true in rRe circumstances that a loss of a neutral in mains or service cables can liven up metalwork in the property, but with modern concentric style neutral core cables this is virtually impossible unless connection at the secondary substation is loosened or corroded. Extremely uncommon. Biggest issue with TT is nuisance tripping RCDs on small load draws.

 

[driverman]

OP wrote PEN earthing. Is that not a different earthing system to PME?

 

[driverman]

OP... is your supply to the cottage overhead supply from poles?
If so, if you follow the poles down the line supplying your cottage and neighbours, at every other pole you may see green/yellow signs about 6 foot high on the poles indicating PME available.
Like been said, only the DNO can officially make your supply PME

 

[whittledr]

OP... is your supply to the cottage overhead supply from poles?

Hahaha cottage! Suburban 3 bed semi in Birmingham, ain’t no cottage!

 

[whittledr]

Thanks folks for the confirmation of my own thoughts, you added more knowledge to my instincts!

 

[pc1966]

Biggest issue with TT is nuisance tripping RCDs on small load draws.

The use of 100mA delay incomer avoids that in all but the most flaky of installations.

Nuisance trips of 30mA 'instant' RCD/RCBO is just a part of modern life, though at least with RCBO the impact is a bit less (and probability given less normal leakage per RCBO).