Installing an earth in my house

[paul1970]

After years of suffering the little tingles so common in Thailand I have finally had enough and am going to be installing an earth in my rented house. I will be doing the work myself as I don't trust any Thai spark further than I could hit them with a static shock.

I have done residential electrical installation in the past to UK wiring regs so am familiar with equipotential bonding but was wondering if the steel trusses in my attic should have an earth connection made to them?

Worst thing I've seen so far while doing this project is the house when it was wired (accordingly to european standards according to the owner) was wired with about half of the live wiring done in GREEN!!! wire..<deleted>!. Luckily I had the sense to open the CU and checking the state of play rather than assuming any green wire I was going to come across would be earthed...TIT.

[Crossy]

Your roof trusses are probably already a very good ground (Google Ufer ground), ours are actually better than the 2m rod I bashed in, by all means connect the trusses to your grounding system, every little helps.

Since this is a rental you may not wish to spend pots grounding all and sundry.

Install a front-end RCBO if you don't already have one then concentrate on providing grounds to any Class-1 appliances you have:- your PC, showers, aircon, washing machine, microwave etc.

You could use a local rod for each appliance (or group of appliances), or run a wire to the roof trusses, or do a pukka job and run the grounds back to the consumer unit and thence to a single 2m rod. With the RCBO any of the options would provide a significant improvement in safety and kill off those (sometimes not so) little tingles.

As many like to say, Up2U.

[paul1970]

Thanks Crossy, never would have thought that concrete would have better conductivity than soil, learn something new everyday. Just sank the earth rod yesterday, was quite surprised how soft the soil was, I was expecting it to be much harder.

Won't be going mad and grounding everything, just all the sockets especially the outside ones. Anything above head height won't be done. Estimate it will cost no more than 2000 baht, rod was only 150 a few different size reels of green wire and maybe the odd socket or two. Stupid thing is we have mostly all 3 pin sockets but of course no wiring to the earth pin, must be how the original spark got away with telling the owner that it was wired to EU specs .

[Chao Lao Beach]

I had a intersting little discovery today, in the CB box, the shower hot water heaters, (wall mounted) have aearth going (it appears) to the eath bar in the box... but nothng else is connected to that bar and there is no known earth stake., While I am doing aother stuff I will run a cable from the earth bar to out side to another rod in the ground.

I have an un-used 30m roll of 2X1.5mm, will using that (connect both lines 3mm) be enough ? Inbound into the house is 16mm, but the cable to the hot water appears to be about 4mm. Again it is a rental.

(Note for Crossy, the new box 2nd circuit will be properly earth indipendantly.)

[Crossy]

@CLB I believe you have a front end RCBO (Safe-T-Cut) in which case your 3mm² would be adequate (and far, far better than the current nothing).

Normally one wouldn't use anything less than 6mm² for a main earth mainly due to the danger of physical damage to the cable.

[wpcoe]

When the roof trusses or water pipes are used for grounding/earthing purposes, does it create any risk that a person who happens to touch the metal roof rafters or a metal water pipe would be subject to a jolt if something in the circuit was sending current to the Mother Earth?

[2fishin2]

Thai water pipes are PVC, cant ground to them. I dont understand a roof truss being a preferred grounding point? Wouldnt it be dangerous?

[IMHO]

Thai water pipes are PVC, cant ground to them. I dont understand a roof truss being a preferred grounding point? Wouldnt it be dangerous?

Steel trusses are generally welded to the steel rebar in the supporting posts, which generally run down to footings in the ground. How good is the ground quality though? Normal building practices dictate that no rebar gets exposed, otherwise you risk the structural integrity.

My guess is, not so good - but OTOH it's not a difficult thing to test either.

[Crossy]

Thai water pipes are PVC, cant ground to them. I dont understand a roof truss being a preferred grounding point? Wouldnt it be dangerous?

No, because, even if not intentionally bonded, all the building steel will be electrically connected. So the floor you're standing on (via the re-mesh) will be at the same potential as the roof metalwork or any grounded equipment so no shock, even if "ground" is several hundred volts above "earth" (think birds sat on the 25kV supply).