My Electrical Nightmare

[Crossy]

IF I understand correctly, IF the power company earths the lines every few poles*, then connecting the incoming neutral wire to the ground bar in the circuit box should be adequate. Am I doing okay, so far?

NO! Your own ground rod forms an essential part of the MEN grounding system, you must have one.

It's difficult to tell from the photos but you do seem to have MEN implemented. But, before linking N and E measure the voltage between them, anything more than a few volts then leave the link out. This of course assumes you have a local ground installed.

Do you have an RCD installed? If not installing one should take priority over messing around with N-E links.

As I noted previously, an RCD and a local ground rod (or your building steel if you can't get a rod in) should be step one.

[electau]

It would appear that the LV distribution neutral is earthed at one or more points, and therefore by definition it is a multiple earthed neutral.

As far as the electrical installation is concerned there is no legislative reason not to still use the TT earthing system.

With a MEN system an earth electrode and main earth conductor must be installed, in the event of a broken neutral or reversed polarity the main earth will hold down the touch voltage to less than 50VAC.

The MEN link must be conected after testing, and the main earth has been confirmed intact

Edited April 4, 2012 by electau

[wpcoe]

NO! Your own ground rod forms an essential part of the MEN grounding system, you must have one.

Okay. I originally thought so, but something I read on one of the threads made me wonder.

It's difficult to tell from the photos but you do seem to have MEN implemented. But, before linking N and E measure the voltage between them, anything more than a few volts then leave the link out. This of course assumes you have a local ground installed.

From what I can tell the N is routed via the earth bar and there is an earth wire leading from the bar to the roof rafters. Or, do you mean something else when you say "linking N and E"?

Do you have an RCD installed? If not installing one should take priority over messing around with N-E links.

Not yet, but I forgot that I had asked about that and never followed up: Can I just take a picture of my circuit breaker box and show it to the staff at Home Pro and ask for the proper, corresponding RCDs for the circuits I want to protect? I want to protect the shower water heater, the washing machine, water pump and clothes dryer. Any other vital circuits I need to protect? Is it reasonable to RCD them ALL? I understand that I would want a 30ms (or less?) response time.

Is RCD a true DIY project that a novice can do? i.e. Do you simply shut off the main double-pole breaker, and then the CB's snap out and an RCD snaps in? OR, is this something truly to be left to an electrician?

[Crossy]

From what I can tell the N is routed via the earth bar and there is an earth wire leading from the bar to the roof rafters. Or, do you mean something else when you say "linking N and E"?

That is the Thai way of linking N&E so you're good to go. I'm getting confused by the numerous grounding threads I think

Can I just take a picture of my circuit breaker box and show it to the staff at Home Pro and ask for the proper, corresponding RCDs for the circuits I want to protect? I want to protect the shower water heater, the washing machine, water pump and clothes dryer.

Good idea, but post your pictures here first so we can see exactly what you have and advise accordingly.

Is RCD a true DIY project that a novice can do? i.e. Do you simply shut off the main double-pole breaker, and then the CB's snap out and an RCD snaps in? OR, is this something truly to be left to an electrician?

Depends upon the answer to the previous question. In most cases a competent DIY'er will be able to install. Only in cases where live working (i.e. on the incoming supply) would I advise getting your local sparks to do at least that part.

You'll need basic electrical tools and a multimeter as well as basic electrical knowledge as you need to identify the neutral associated with the circuits you are protecting.

[nellyp]

@nellyp: Are you running your neutral wire via your earthing bar? If I understand what Crossy has been teaching me in other threads, that would enhance your earthing with "MENS".

Here's a diagram from the instruction sheet for the consumer unit in my townhouse:

The neutral wire would go from your knife switch to the earthing bar before it heads to main breaker.

I live in a small town in Issan and actually live in a school's grounds. None of the poles has any kind of earth going from them, and the main pole with the buzzy bits on has an earth wire that has been cut and left dangling. I do not think that it would be worthwhile me trying to do anything with MENS. Do you think that it would make any difference to my situation? Also I'm surprised that the neutral goes to the earthing bar before the main switch, but then again I know nothing about MENS ( unless it's menswear)

[Crossy]

I'm beginning to sound like a broken record here.

Whatever, do NOT that is NOT make a N-E link unless you KNOW that's KNOW that MEN is implemented in your area. This includes the Thai method of running the incoming neutral via the earth bar.

Look on the Wiki page http://en.wikipedia....arthing_systems specifically 'safety risks'.

It's far, far safer to be TT than it would be to be the only N-E link on a system with a failed neutral.

[nellyp]

I'm beginning to sound like a broken record here.

Whatever, do NOT that is NOT make a N-E link unless you KNOW that's KNOW that MEN is implemented in your area. This includes the Thai method of running the incoming neutral via the earth bar.

Look on the Wiki page http://en.wikipedia....arthing_systems specifically 'safety risks'.

It's far, far safer to be TT than it would be to be the only N-E link on a system with a failed neutral.

Cool i will leave well alone and just go with my diagram. I am good to go now but am waiting on home pro for my rcbo for the shower and the Air con ( am only using one in my CU). My local electrical supply shop has a basic box with 2 MCBs and a main off and on switch. Could I buy a separate RCBO to run alongside this or would that be too dangerous

[Crossy]

Cool i will leave well alone and just go with my diagram. I am good to go now but am waiting on home pro for my rcbo for the shower and the Air con ( am only using one in my CU). My local electrical supply shop has a basic box with 2 MCBs and a main off and on switch. Could I buy a separate RCBO to run alongside this or would that be too dangerous

Nothing to stop you doing that just not very elegant, I'd wait until you have all the bits to do a neat job, external bits will get added soon enough.

You should feed your external RCBO from the switched side of the main switch in order to maintain a single point of isolation. Although not decreed in any regulations keeping a single switch that kills the entire installation is a good idea.

[thaibeachlovers]

NO! Your own ground rod forms an essential part of the MEN grounding system, you must have one.

Okay. I originally thought so, but something I read on one of the threads made me wonder.

It's difficult to tell from the photos but you do seem to have MEN implemented. But, before linking N and E measure the voltage between them, anything more than a few volts then leave the link out. This of course assumes you have a local ground installed.

From what I can tell the N is routed via the earth bar and there is an earth wire leading from the bar to the roof rafters. Or, do you mean something else when you say "linking N and E"?

Do you have an RCD installed? If not installing one should take priority over messing around with N-E links.

Not yet, but I forgot that I had asked about that and never followed up: Can I just take a picture of my circuit breaker box and show it to the staff at Home Pro and ask for the proper, corresponding RCDs for the circuits I want to protect? I want to protect the shower water heater, the washing machine, water pump and clothes dryer. Any other vital circuits I need to protect? Is it reasonable to RCD them ALL? I understand that I would want a 30ms (or less?) response time.

Is RCD a true DIY project that a novice can do? i.e. Do you simply shut off the main double-pole breaker, and then the CB's snap out and an RCD snaps in? OR, is this something truly to be left to an electrician?

I wouldn't ask Home Pro staff anything. They don't seem to have a clue about the things they sell- I watched them destroy an appliance trying to get a drip tray out!

Also, I found Home Pro to have a limited range of RCDs, and they were expensive.

I found a local electrical supplier to be better value.

[thaibeachlovers]

OP, you wrote <With a meter long copper pole that has the earth wire welded to it> Is that correct? An earth rod should be 3 meters long, or two shorter rods at least two meters apart, joined together, or so I've been informed. The so called electricians that installed my shower heater tried the short earth rod trick, but at least I was able to sort that out by myself.

I've now rewired 2 Thai houses- the first had only 1 10 amp circuit breaker for everything, no earth and dead animals in the fan control boxes. The second had no RCD, and no earths, but it did have a few circuit breakers, not all of which were in use.

feel free to PM me about my experiences.

[electau]

OP, you wrote <With a meter long copper pole that has the earth wire welded to it> Is that correct? An earth rod should be 3 meters long, or two shorter rods at least two meters apart, joined together, or so I've been informed. The so called electricians that installed my shower heater tried the short earth rod trick, but at least I was able to sort that out by myself.

I've now rewired 2 Thai houses- the first had only 1 10 amp circuit breaker for everything, no earth and dead animals in the fan control boxes. The second had no RCD, and no earths, but it did have a few circuit breakers, not all of which were in use.

feel free to PM me about my experiences.

One (1) earth electrode 1.8 to 2.4 metres in the ground 13mm or 16mm copper clad steel with the main earth conductor affixed to the electrode by means of an approved clamp or 2 galv or stainless steel U- bolts.

This will give sufficient contact area with the soil to meet earthing requirements, The soil resistance is uncontrolled.

Bond any metalwork that enters the ground to the main earth eg water mains, rebar etc. if accessible.

[bankruatsteve]

RE: Ground rod: Doesn't the type of ground/dirt make a difference? ie: if it's mostly clay it seems like it could do with 1m or less. With sand maybe 3m not enough?

[Crossy]

RE: Ground rod: Doesn't the type of ground/dirt make a difference? ie: if it's mostly clay it seems like it could do with 1m or less. With sand maybe 3m not enough?

Indeed it does. This is one major difference between AS3000, the NEC and UK regs BS7671.

AS3000 and NEC (on which the Thai regulations are, at least partially, based) are prescriptive, defining exactly what is to code and what isn't. i.e. Bash in a 2m rod, period! No (or very few) actual measurements required.

BS7671 is descriptive, stating the requirements for the earth electrode (and its associated wiring) in terms of it opening the protective device in a defined period (i.e. its resistance). How you achieve the requirement is up to you as the system designer, if a 1m rod demonstrates by measurement that meets the resistance requirements then that's all that is needed. If it doesn't then you need to add electrodes, mats or earth improving products (Bentonite and coal dust are very good). A detailed inspection report with various circuit measurement values forms part of the legal documentation needed for the local Building Control authority to issue its certification. I can't speak for Aus, but US electrical inspections are largely visual, it's either to code or it isn't, there is no latitude for actually designing the circuits.

To be honest, the simple 'do it this way and it will be OK' works for the domestic installations we're interested in and I'm happy to agree.

The one thing I really want to measure is the quality of the ground, unfortunately specialist equipment is needed for this, so we are again stuck with the prescriptive technique.

[electau]

AS3000 requires the earth electrode to be a minimum of 13mm copper clad steel at a minimum depth of 1.2metres in the soil. The contact area of the electrode in contact with the soil is a minimum value. Soil resistance is uncontrolled and is not required to be tested. Other types of electrode are permitted.

AS3000 requirements are not prescriptive. Other methods are permiited as long as the minimum requirements of the standard are maintained. Values may be min, max or mean as required.

Supply Authorities carry out earth resistance tests, max 10ohms for LV systems. AS3000 does not cover public electrical distribution systems.

Edited April 11, 2012 by electau