Earth across 3 independent rooms

[regedit]

Is this proposal by my electrician ok - 3 rooms-for-rent, each with their own consumer unit, and each with their own live supply and neutral. For the earth, does each consumer unit need to have its own independent earth (so 3 cables will connect to the earth rod) or is it ok for them to be connected to one cable which runs to the earth rod, like in this diagram?

Thanks.

 

[OneMoreFarang]

No answer until now so let me try:

One earth cable like in your drawing should do the job.

But if you want to make sure that even in bad scenarios there are no problems, then separate cables are definitely better. 

 

If you ask for Thai regulations: I don't know if it is according to regulations.

 

 

[Crossy]

I don't like joints in earths, especially if they will be concealed, you don't know it's failed until you die!

 

The way I would do it is select one CU as the "main CU" (the one at which the supply arrives would be favourite) and use the earth bar in that one as a Main Earth Terminal (MET). A wire from each CU to the MET, then one wire from there to the rod.

 

All the electrical suppliers have earth bars available so you could put one of those in a box and use it as the MET.

 

How are you arranging your MEN (N-E) link?

 

[regedit]

Thanks - good point. In the house on the same site (which has its own earth rod some 20 meters away from this earth rod) the neutral and earth are connected in its consumer unit, so I assumed same would be required here?

[Crossy]

2 hours ago, regedit said:

Thanks - good point. In the house on the same site (which has its own earth rod some 20 meters away from this earth rod) the neutral and earth are connected in its consumer unit, so I assumed same would be required here?

 

There should only be one N-E connection on a supply. Sketch out what you intend doing and we can critique.

[regedit]

Thanks Crossy. See attached sketch - existing building has 10 rooms, all with their own consumer unit, and each consumer units has the earth connected to the neutral, so your comment is a bit of a concern. Should these N-E connections be removed? I don't think there is a N-E connection in the distribution board but will take a photo (by distribution board I mean where the main feed comes in and then the live and neutrals get passed to each room. The earths for rooms 1-10 connect to a MET in the distribution board).

 

 

For the new rooms (11-13) a second earth rod needs to be used since they are 20m away from the first earth rod. These 3 rooms are also closer to the main meter, so plan is to connect to it again. I sketched out the intended earth connections based on your earlier comment - all 3 earths connecting in room 11 consumer unit.

[Crossy]

5 hours ago, regedit said:

Should these N-E connections be removed?

 

If we were in the US the inspector would be running around screaming!

 

In reality there's no issue keeping them, provided there are no RCDs/RCBOs "upstream" of the link.

 

Your plan looks fine to me ???? 

[regedit]

47 minutes ago, Crossy said:

 

If we were in the US the inspector would be running around screaming!

 

In reality there's no issue keeping them, provided there are no RCDs/RCBOs "upstream" of the link.

 

Your plan looks fine to me ???? 

Thanks, but what do you mean by upstream of the link (which link?). All the CUs have RCDs, and a few rooms have shower units with built in RCBOs (or is that downstream?). The distribution board has RCDs which act as kill-switches for the live supply to each room.

[Crossy]

51 minutes ago, regedit said:

The distribution board has RCDs which act as kill-switches for the live supply to each room.

 

If you have N-E links in your CUs then the RCDs in the dizzy board won't stay on.

 

So, link N-E in the dizzy board, needs a longer bit of green wire.

[regedit]

My bad, they are MCBs in the distribution board, not RCDs.

 

For the new rooms 11-13 assume best not to have E-N connected in the 3 consumer units?

Edited June 1, 2023 by regedit

[Robin]

My experience of Thai Electricians/Wiring, would make me go round each room ans socket and check that there is a good connection to the main earth.  So easy to just put in a green wire that goes nowhere.

[Crossy]

1 hour ago, regedit said:

My bad, they are MCBs in the distribution board, not RCDs.

 

For the new rooms 11-13 assume best not to have E-N connected in the 3 consumer units?

 

If you have MCBs in the DB then keep the N-E links in the CUs.

[bluejets]

There are some aspects of your drawing that are incorrect depending on the following...........

 

Are the buildings all on one land title?

Is the main metering either one 3 phase or three 1 phase meters, or are there separate meters for the two distribution boards..?

 

Either way, earthing for #2 board should originate at the #2 board, not the earth stake of somewhere along the way.

 

There are other issues as well depending on you answers to the above.