Neutral and earth

[cloudhopper]

Hi I am getting some conflicting advice re the neutral and earth connection. It seems to me that the neutral must be connected to earth at the main circuit breaker panel (in systems without fault protection) in order for the circuit breaker to have any chance of tripping with a hot/chassis fault. Others say that connecting the neutral to earth at the main box will cause problems in the neighborhood distribution circuit. My supply is 2 wire single phase to a standard breaker panel with no other fault protection. Can anyone clear this up? TIA

Edited October 16, 2013 by cloudhopper

[Crossy]

Is this a new installation? If so the MEA/PEA inspector will expect N-E to be linked as shown here (yes, the incoming neutral goes via the earth bar, apparently how it's done in the US NEC code):

If it's an existing installation do NOT link N-E unless you know for certain that MEN is implemented in your area, there is a distinct possibility of introducing a hazard.

Do you have any form of earth-leakage protection (RCD, Safe-T-Cut)? If not installing one should be your first port of call.

Do you have a ground rod? Is it connected to your 3-pin outlets and Class-1 appliances (typically water heaters and A/C)?

[bankruatsteve]

Also, circuit breakers provide over current protection which a fault may/may not exceed regardless of N-E bonding. Proper grounding is necessary for Class-1 appliances and RCD's will provide added assurance.

[cloudhopper]

It is an existing rural installation with a ground rod and 3 wires to all sockets. No other fault protection. I do not know the term MEN. Supply appears to be a single phase taken from one leg of a 3 phase through a pole transformer and serving several homes.

[bankruatsteve]

As discussed many times in this forum, even though you have grounded outlets, it is not uncommon for class-1 appliances, tools, etc. to be sold without the 3-prong (including ground) plug here in Thailand. (That seems to be changing though.)

MEN is like it is in the states where N and E are bonded at the transformer and CU. In the states, that's needed for the 110v system to work.

You should add a front end RCD to your CU or put RCBO on your receptacle circuits for best fault protection.

[Forkinhades]

Any Neutral to Earth connections need to be done on the supply side (PEA). This is sometimes done inside a consumer unit, where you will in fact have 2 separate neutral bars. You should not attempt to do it yourself.

You have a TT system, which in accordance with the thai code 'must' have RCD protection. But TIT, and nobody complies with regulations here in LOS.

If you don't have RCD protection, then I suggest get it, and your electrical safety problems will be quite possibly solved.

Sent from my GT-I9300 using Thaivisa Connect Thailand mobile app

[Crossy]

+1 Forky.

Have a look at the diagram on post #2, this is the ONLY PEA-acceptable MEN connection (it's the same as the US NEC system).

It's invariably done in the CU or, if you have one fitted, the front end of the Safe-T-Cut box (it's like that in the instructions).

[bankruatsteve]

Back to the original post... the only problem I can think of when bonding the N to E at the CU in a non-MEN situation for the neighborhood distribution is if somebody switches N and L at the transformer. Which does seem to happen. Otherwise, shouldn't be an issue. ?

[FiftyTwo]

Back to the original post... the only problem I can think of when bonding the N to E at the CU in a non-MEN situation for the neighborhood distribution is if somebody switches N and L at the transformer. Which does seem to happen. Otherwise, shouldn't be an issue. ?

Strange you should mention that.

I moved into a new build last month, on all the shower heater and air con connection points, neutral was live no matter what position the RCDs were in. Live was ground, no matter what position the RCDs were in.

They had reversed the Live and Neutral feeds into the house. It was fixed by them pulling wires out of the meter on the pole outside the house. Don't know how many other houses in the 200+ moobaan were wired wrong, but very dangerous.

[IMHO]

Back to the original post... the only problem I can think of when bonding the N to E at the CU in a non-MEN situation for the neighborhood distribution is if somebody switches N and L at the transformer. Which does seem to happen. Otherwise, shouldn't be an issue. ?

Strange you should mention that.

I moved into a new build last month, on all the shower heater and air con connection points, neutral was live no matter what position the RCDs were in. Live was ground, no matter what position the RCDs were in.

They had reversed the Live and Neutral feeds into the house. It was fixed by them pulling wires out of the meter on the pole outside the house. Don't know how many other houses in the 200+ moobaan were wired wrong, but very dangerous.

We have come across transposed N-A numerous times. Especially scary considering a 20 baht test light is all you need to get it right..

[Crossy]

Back to the original post... the only problem I can think of when bonding the N to E at the CU in a non-MEN situation for the neighborhood distribution is if somebody switches N and L at the transformer. Which does seem to happen. Otherwise, shouldn't be an issue. ?

Consider what happens if the neutral goes open between you and the Tx, specifically if you are the only one with a N-E link (the whole Tx neutral current flows down your earth link and rod).

It is for this reason that MEN (PME) has only recently become common in the UK, even so there was an incident a couple of years ago when a whole row of cottages blew up then burned down due to an open neutral in a PME situation. Turns out that the neutral current flowed via the gas pipe bond with predictable results.

[Pib]

My 6 year old home in western Bangkok, part of a very large gated moobaan where the great majority of the homes were built and still being built by mainly one developer over the last 15-20 years, uses the TT grounding setup (i.e., Neutral and Ground not connected). Over the years I've had a chance to look at few of my neighbor's main circuit boxes helping them to change circuit breakers and their boxes were TT grounded also....I also asked the developer's lead engineer a couple years back about the grounding method and he said that's the way they still wire up new houses they build in the moobaan...maybe it's just because my area/moobaan started off as a TT grounding method years back, has since developed to around 750 homes, and they don't want to intermix grounding methods among the homes....then again, maybe some of the homes in my moobaan do have the Neutral and Earth connected....I'm not about to go around to 750 homes to find out.