Earthing arrangement advice please

Dave 85 · Jul 18, 2012

Hi lads
Looked at a job today
3036 Fuseboard
Looks like TT but only 2.5mm earths visible, couldn't find a stake and 126ohms Ze on a wet day.
There is an old earth leakage breaker, it did not trip when put under 500mA RCD test, does this mean its f***ked?
The supply fuse looks Like a TNCS head but no earth coming out of it. I take it I cant just PME it of my own accord?
This would be ideal as the outside seems to be concrete everywhere so getting a stake in would be a challenge.

Im gonna recommend a new CU to the client. If they dont go for this is it acceptable to replace the earth trip with a 100mA RCD?
Im also recommending upgade of main earth and bonding but need to know for def that PME'ing is out of the question.....

Any advice would be very much appreciated

Oh yeah...here are some photos...

Octopus · Jul 18, 2012

Is the home dependent on the water or gas main for its earth? Seen many like this....

Dave 85 · Jul 18, 2012

Murdoch said:
Is the home dependent on the water or gas main for its earth? Seen many like this....

This is what I suspect

Octopus · Jul 18, 2012

Dave 85 said:
This is what I suspect

Me thinks its time to stick a rod or 2 in!

Guest123 · Jul 18, 2012

That unit is a VO-ELCB, putting any amount of mA through it won't make it do anything due to it being VO (voltage operated).

These units are obsolete now as many of them have malfunctioned and should be removed/upgraded sooner rather than later.

topquark · Jul 18, 2012

It says it's voltage operated Dave, so no, a 500mA RCD test will tell you "not a lot". Does the test button work on It?

oldtimer · Jul 18, 2012

Murdoch said:
Is the home dependent on the water or gas main for its earth? Seen many like this....

Could be thing is they change the pipework to plastic then fail to inform the household then some poor spark turns up to find a high Ze

somersetsparks · Jul 18, 2012

I wouldn't attempt to test that Voltage trip, I pushed the test button on one once just messsing around when I was apprentice and we ended up replacing it with an RCD for free, the customer said 'it was fine before you touched it'!

Dave 85 · Jul 18, 2012

topquark said:
It says it's voltage operated Dave, so no, a 500mA RCD test will tell you "not a lot". Does the test button work on It?

Yeah it does

Dave 85 · Jul 18, 2012

What about converting it to TNCS? is this possible?

topquark · Jul 18, 2012

Dave 85 said:
Yeah it does

Then it's WAD (working as designed). As Lenny (lighting fingers) said, they should be replaced anyway.

- - - Updated - - -

Dave 85 said:
What about converting it to TNCS? is this possible?

Depends what you have out in the street, you'd need to ask the DNO (it's not available in all areas).

IQ Electrical · Jul 18, 2012

If a VOELCB on a TT system fails to operate when tested with an instrument or integral test button, this would warrant a Classification Code C2 (potentially dangerous).

But, subject to the VOELCB being proved to operate correctly, continued reliance on it for fault protection (protection against indirect contact) would normally warrant a Classification Code C3 (improvement recommended).

However, if the VOELCB relies on a water pipe not permitted by Regulation 542.2.4 to be a means of earthing, this should attract a Classification Code C2 (potentially dangerous).

From ESC