Jump to content
BANGKOK 27 March 2019 07:13
ross163103

Ground issues/farang electrician

Recommended Posts

3 hours ago, Crossy said:

These two leaflets from PEA (so official) show the recommended connections (which will get you past the PEA inspection). Worth a look for the pictures.

 

groundwire.pdf 14.86 MB · 3 downloads

 

Groundwire Mk2 book-Manual.pdf 803.56 kB · 8 downloads

 

And the important diagram with translations (the notes in brackets are my clarifications).

 

Groundwire Mk2 book-Manual-1 diagram.jpg

Hi, can you please explain why incoming neutral is connected to ground?

How does it affect residual current protection , leakage, safety, stability, etc

Cheers. 

Share this post


Link to post
Share on other sites

@Rally123 thanks for the photos.

 

Have you checked your supply polarity? i.e. Live really is live, Neutral is neutral. One of the potential issues with using MEN is if the polarity is reversed then the "grounded" metalwork can move away (sometimes well away) from being at ground voltage.

 

Where in your box were neutral and earth connected, like the diagrams I showed or a link between the N bar and E bar?

 

What you have now, TT with a front end RCBO is quite safe and legal (it wouldn't be in Aus) so it's fine to leave alone.

 

BUT I see what looks like a black wire connected to the incoming live terminal of your RCBO. It may be a photo artifact, but it's not then whatever is on the other end has zero overcurrent or earth leakage protection, also where does the neutral from whatever it is go?

 

This wire;-

 

IMG_20190217_095358_1.jpg.38de0749307916beeeb0ff2186322c4b.jpg

 

  • Like 1

Share this post


Link to post
Share on other sites
48 minutes ago, stud858 said:

Hi, can you please explain why incoming neutral is connected to ground?

How does it affect residual current protection , leakage, safety, stability, etc

Cheers. 

 

Wikipedia has quite a good discussion on earthing systems here https://en.wikipedia.org/wiki/Earthing_system

 

Thailand is either TT, TNC-S (which has N and E connected at the dizzy board) and maybe TN-S in some condo units.

 

TN-S and TNC-S give a solid metallic connection between the ground bar in your distribution box and the (grounded) neutral/star point at the transformer. Any short beween live and earth will happily open an MCB or fuse and kill the power.

 

A TT system with an earth rod of say 50 ohms impedance will cause a current of only 4.4A to flow in the event of a L-E short, even your lighting circuit will happily supply that without the breaker or fuse opening. Also whilst that 4A or so is flowing anything connected to "earth" will be near mains potential and lethal. This is where an RCD or RCBO comes in, it detects a flow of more than 30mA to earth and opens, killing the power.

 

An RCD or RCBO will also open if you get hold of a live wire (an MCB won't) and, whilst you'll still get a whallop, should save your life.

 

Any N-E connection must be BEFORE any RCD protection or the RCD may not stay on, or may trip at random.

 

 

  • Thanks 2

Share this post


Link to post
Share on other sites
5 hours ago, Crossy said:

 

I don't want to worry you. But this is correct for the Thai implementation of MEN.

 

Removing that connection can have a detrimental effect on safety, particularly if you don't have an RCD/RCBO.

 

If was implementing MEN here and my distribution earth terminal potential kept rising above actual ground I would begin to wonder whats going on with the neutral connections down stream and disconnect the MEN link. I personally don't think distribution standards here are anywhere near high enough for everyone to use multiple earthing.

 

I often wonder how many earth rods start steaming when transformer neutrals fall off.
 

Share this post


Link to post
Share on other sites

There are many arguments for and against MEN (with TNC-S), a broken neutral is high on the list particularly when the supply is via aerials.

 

The only point I'll make is that in order to get past the PEA / MEA inspection of a new installation so you can get a permanent meter you'll need to implement MEN in the Thai manner.

 

Once your permanent meter is in place you can pretty much do as you like, switch back to TT if you like, provided you have an RCD it's pretty safe.

 

 

  • Like 2

Share this post


Link to post
Share on other sites
1 hour ago, Crossy said:

where does the neutral from whatever it is go?

IMG_20190217_095358_1.jpg.38de0749307916beeeb0ff2186322c4b.jpg

 

That 'neutral wire' is the 'live' wire that goes to 'power surge' protector.  

And I just checked with the wife. She agreed that all the electrician did to sort out our problem was to separate the  earths from the neutral terminal.

IMG_20190217_122555.jpg

  • Like 1

Share this post


Link to post
Share on other sites

Can someone with some electrical knowledge tell me if this breaker box looks correctly wired? I realize you can't see every wire and where it goes, but I'm particularly interested in the earth and neutral connections. I had an RCBO breaker installed and it has worked on some circuits but there are others where I still get a tickle when touching the connected appliance. I don't understand why the RCBO won't trip on all the circuits in the house. I won't attempt anything on my own as I'm not qualified but just want some info until I find an electrician. Also, do you think it's better to have individual RCBO's on each circuit as additional protection or is this overkill because the main breaker has one? Thanks in advance.

Breaker 1.JPG

Breaker 2.JPG

Breaker 3.JPG

Share this post


Link to post
Share on other sites

FYI:  Most RCD (RCBO) will not detect "tingles" as they are well below the normal 30 ma trip current.  A "tingle" is almost always the result of no (or improper) ground to whatever you are getting the tingle from.

 

My observation of your box is that there are less connections to the neutral bar than there are MCBs (borrowed neutrals?).  And, only two ground connections - maybe why some circuits have tingles.  Edit: Also an interesting application of wire colors.  Whew.

Edited by bankruatsteve
  • Haha 1

Share this post


Link to post
Share on other sites
8 minutes ago, bankruatsteve said:

My observation of your box is that there are less connections to the neutral bar than there are MCBs (borrowed neutrals?).  And, only two ground connections - maybe why some circuits have tingles.  Edit: Also an interesting application of wire colors.  Whew.

 

That said, it does do MEN correctly 🙂

 

I would hope that one of those ground connections goes to a rod somewhere, if it doesn't then you should install one.

 

Share this post


Link to post
Share on other sites
36 minutes ago, Rally123 said:

That 'neutral wire' is the 'live' wire that goes to 'power surge' protector.  

 

The protector really should have some sort of over-current protection just in case its own built-in protection fails. What did the device's instructions have to say?

 

As noted before, what you have is pretty safe, do check the polarity just in case.

 

Share this post


Link to post
Share on other sites
15 minutes ago, Crossy said:

What did the device's instructions have to say?

I no longer have them. 

I just read this regarding a solution to the OP's problem.

Quote

I have noted that at the meter box on the pole, that the earth is connected to the Neutral. 

Quote

 

This sounds like a TNCS earthing arrangement. There could also be an earth rod on your property usually at the first point of entry. The E-N connection on the council side is normal.

To receive an electric shock there is usually two completely separate problems occurring simultaneously. 

Firstly there's usually an insulation fault (low IR). Insulation is what prevents current 'leaking' to earth in a healthy or compliant circuit. As the value or effectiveness of the insulation decreases the leakage current to earth increases. 

The key word here is earth (ground for our US members). The current takes the path of least resistance so if the earth is good (low resistance) then the fault current flows freely away down this path instead of flowing through someone who touches the appliance with the insulation problem. 

This leads to the second problem required when you get a shock or tingling in your case. If the earth wiring (cpc) is high resistance then any fault current present on a circuit or appliance will happily look for an alternative route of lower resistance to flow to earth. In most cases this is the poor soul who comes into contact with it.

Okay, I've tortured you with enough technical rubbish so I'll suggest a few things you might do to fix it.
You say you still get tingling with the HWC circuit isolated, this kinda throws a spanner in most of the usual suspects.
 

  1. I'd certainly double check any earth bonding around the cylinder, remake the bonding connections and clean the copper under all the straps so it's shiny.
  2. Visually check all the connection points at the cylinder, the isolator switch and in the DB. Test the earth impedance of the cylinder earth and preferrably use a tester such as a loop impedance tester that can put a high current pulse (40Amps) through the earthing.
  3. Megger test the cylinder element at 1000v to check its insulation integrity, it should be at least 10Mohms.




All these tests so far are basic bread and butter and from what you say I doubt you'll find the problem there but rather start with the easy obvious stuff and rule it all out of the equation before you go complicated. Once you know the cylinder and its associated circuit are fine it's time to get into the DB. Visual first, check all earth and power connections for tightness, corrosion or overheating damage. Determine if you have an earth rod on the property which would indicate you have a PME system. If you do then impedance test the rod on its own and disconnected (Ra test), also visually inspect the wiring connections to the rod. Same goes for any bonding from the DB to plumbing, check the integrity of the cabling, straps and connections.

If everything checks out then it starts getting complicated I'm afraid. I'll try explain but I can't advise on how to proceed with localizing without seeing the shower and the surrounding areas. There's actually 2 directions you can get a shock. The usual direction is where you have your feet on a zero volt ground and you put your hand or fingers something that has a fault and a high touch voltage. The fault current then runs from the faulty item and through your body to ground or earth. 

Click image for larger version.   Name: Shock.jpg  Views: 2269  Size: 24.9 KB  ID: 3118

The other way you can get a shock is if you're standing on a floor that is at a voltage above zero and you touch a good earth. This is always a possibility with a shower becase they often leak moisture into the surrounding area and the taps are nearly always a good earth point. 

I've seen several similar scenarios that are a bugger to locate and usually end up with tiles removed, jackhammering and waterproofing being required. You need to think out of the box as well as in three dimensions. The trick is to find all the electrical cabling and points in the vicinity of the shower and insulation test those circuits. I've seen damp problems in sockets in adjacent bedrooms giving shocks to users of the shower in the next room. I've also seen a stove isolater that was getting damp because of a bathroom leak directly above giving shocks to people at the wash basin. I've also found one problem years ago where tree roots had grown through a drain pipe and a nearby garden light circuit connection was causing tingling at a kitchen sink through the drain water. 

These kinds of faults aren't easy to find even with state of the art test equipment and the patience of Job. I wish you luck and hopefully it's something obvious. I would also advise caution if you're not electrically competent, it's easy to get a fatal shock when working on equipment, circuits and in DB's, especially when there's an underlying fault that might have unexpected results. Even earth wiring can become 220V live when it's disconnected!!! You need to know how to prove isolation as well as having the necessary testing equipment. If you're not competent or unsure of anything please seek professional assistance. You've been warned.

 

 

Share this post


Link to post
Share on other sites
32 minutes ago, bankruatsteve said:

FYI:  Most RCD (RCBO) will not detect "tingles" as they are well below the normal 30 ma trip current.  A "tingle" is almost always the result of no (or improper) ground to whatever you are getting the tingle from.

 

My observation of your box is that there are less connections to the neutral bar than there are MCBs (borrowed neutrals?).  And, only two ground connections - maybe why some circuits have tingles.  Edit: Also an interesting application of wire colors.  Whew.

Agree  about the rainbow effect.

Share this post


Link to post
Share on other sites
1 hour ago, bankruatsteve said:

Edit: Also an interesting application of wire colors.  Whew.

Yes, I guess "Somchai" liked the colors....or these colors were cheaper. LOL I'm done with Thai electricians; I'm sure there are some good qualified ones out there.....but I can't find them. 

Share this post


Link to post
Share on other sites
1 hour ago, Crossy said:

I would hope that one of those ground connections goes to a rod somewhere, if it doesn't then you should install one.

I put one in years ago--I pounded it into the soil so I know that part is right, but it has since been concreted/tiled over--I know, not a good idea, so I don't know the condition of it. I know that now and will install another one just in case the original has corroded down to nothing. At the time of concreting/tiling I didn't think the copper would corrode, but I read on this forum of another person that found his earth rod corroded while doing some gardening; can't remember exactly but seems like it was REAL short.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...