Hi Zs

[studentspark]

Hi Zs on sockets 13-14 ohms


The install has a VOELCB

Untitled

• studentspark
• 14 Aug 2010
• 2

I can't see a earthing conductor at the incommer

Untitled

• studentspark
• 14 Aug 2010
• 2

I am presuming the earth is provided by a TT setup

Now I have never worked on a TT system before, I understand that they have to be RCD protected.

Did not get chance to look any closer.

Advised to get an electrician in to check it out, but I have a few questions

Electrician called, suggested changing the VOELCB, and said there is probably a rod in the cupboard.

Is it common to place the rod inside the house?

Is the VOELCB the pre curser to the RCD for TT systems?

How do you know if you have a TT system ?
by that I mean the earthing cable could be going anywhere, bonding for example, how do you know it going to a rod.

What would you do in this situation?

 

[333rocky333]

Whats the earth wire on the rcd unit did you follow that

 

[ericmark]

Electrician called, suggested changing the VOELCB, and said there is probably a rod in the cupboard.

Is it common to place the rod inside the house?

I have put earth rods under floor boards it saves the problem of fitting covers as the soil close to an earth rod under fault conditions can have a very steep voltage gradient so you want to keep people away from the rod.

Is the VOELCB the pre curser to the RCD for TT systems?

Yes but it was too easy for the earth to become short circuited and for it to stop working so no longer used.

How do you know if you have a TT system ?
by that I mean the earthing cable could be going anywhere, bonding for example, how do you know it going to a rod.

This is of course a problem and that's why we must have assess to the rod to test. All too often the water and gas pipes are the only earth but using an earth loop impedance meter we will normally have a good idea of what we are looking for as TN systems have a reading below 0.8 ohms and with TN-C-S below 0.35 ohms.

What would you do in this situation?

The ELCB-v of course needs changing and one has to consider how. There is nothing wrong in using the ELCB as an isolator and have it feed a new consumer unit with RCD's in consumer unit. I would be looking at how many ways and what it feed before final recommendation.

Likely there will be a problem with the earth rod and a larger rod with thicker cable will likely be required.

I would start by ringing DNO and asking what the earthing system is. They have to tell you not you telling them. Likely they will not know and will have to send some one to have a look. I would then tell them I called because neighbouring houses have a TN-C-S system even if they don't. Likely they will then check the ELI and if low enough will make your house into TN-C-S as well without charge.

If it does no go according to plan then it's big hammer job and new earth rods. But worth trying it on first.

Remember the DNO does not have to provide an earth but they do have to give same system to all property supplied from same transformer. Hard luck if a petrol station is near by.