Hello. I'm American and have an above-average understanding of electrical wiring. I'm comfortable installing new lights, sockets, breakers, etc.

 

We're building a new house (having it built) and I am checking the electrical wiring.

 

In America (110 volt system), if you check the neutral - ground connection, it should have minimal voltage,  0-1.5 volts maximum. Any more, and your neutral line is carrying too much voltage.

 

When I measure here, I'm getting 5 - 10 volts. It is not stable either, it bounces all over the place, sometimes spiking over 10 volts.

 

I don't know much about 220 volt systems. Does anyone know if my readings are normal?

 

Thanks.

 

 

We have a dedicated forum for such posts.

 

MOVED

35 minutes ago, Thomas72 said:

 

 

Hello. I'm American and have an above-average understanding of electrical wiring. I'm comfortable installing new lights, sockets, breakers, etc.

 

We're building a new house (having it built) and I am checking the electrical wiring.

 

In America (110 volt system), if you check the neutral - ground connection, it should have minimal voltage,  0-1.5 volts maximum. Any more, and your neutral line is carrying too much voltage.

 

When I measure here, I'm getting 5 - 10 volts. It is not stable either, it bounces all over the place, sometimes spiking over 10 volts.

 

I don't know much about 220 volt systems. Does anyone know if my readings are normal?

 

Thanks.

 

 

 

Ya want the Electrical forum, you will be moved. 

 

You probably have a TT system with a local earth rod, the neutral being earthed at the transformer only.

 

The N-E voltage will vary with load (IR volt drop on the neutral), in reality it's nothing to worry about unless it gets silly (say 20V or more).

 

More important would be the presence of an RCBO/RCD (GFI in US-speak). Can you post a photo of your distribution board with the lid off (care please) so we can see exactly what you have.

 

You say this is a new build, does that mean it's a new supply (currently a construction supply)? If so you will need to follow the Thai requirement for using TN-C-S with MEN which ought to result in a much lower N-E voltage.

 

This PEA document may be handy Groundwire Mk2 book-Manual.pdf

 

The important diagram with translations.

 

 

 

I'm going with Crossy's hunch, that "You probably have a TT system with a local earth rod, the neutral being earthed at the transformer only."

 

Even though our local electrical grid in the village is MEN (Multiple Earth Neutral, neutral bonded to ground on every third power pole), local electricians never seem to make the N-E Bond also in the Consumer Unit (breaker box) where the differential would be cancelled out sooner, so with no local 'bond' your neutral will 'float' above earth-ground a bit more than usual.

 

My house has a local N-E bond in the box, but I still get about 1.24vac at the socket of the washing machine without any load. But then our house utilizes a combination of ufer and multiple earth-ground stakes around the house and outbuildings. And given that non of our neighbors have N-E bonding in their CUs I'm guessing we're getting a bit of earth-ground bleedover from their systems. 

I wish I had found this forum sooner.

 

The house is a new construction. It should be completed in the next week. Today I was inspecting the electrical.. All the lights, switches, sockets, etc. when I came across these voltage readings.

 

The electrician installed a 3 meter earth rod right below the breaker box. They drilled through the slab. I never saw anything like that before.

 

The build is permitted, and extensive construction plans were drafted. I don't have a photo of the breaker box on me. I'll get one ASAP and post it.

 

Thank you so much.

31 minutes ago, Thomas72 said:

The house is a new construction.

 

You will likely have a "construction supply" which is billed at 8 Baht per unit, to get a permanent supply you need to pass a (pretty cursory) inspection but the inspector will expect to see the MEN arrangement shown in my earlier post along with at least a front-end RCBO in the board.

 

I don't have a photo yet but I found the receipt and looked up the main breaker. It's the 63 amp version:

 

https://www.globalhouse.co.th/product/detail/3606480570544

 

We are buying all parts and materials, so it's unlikely any of the contractors are using inferior materials.

 

Here's a screenshot for future posterity:

 

Here's the current meter:

 

It was 6000 baht to install from PEA. I thought it was excessive.

 

You should measure the voltage in the breaker box.  Plugging probes into an outlet is dodgy at best.

14 minutes ago, Thomas72 said:

I don't have a photo yet but I found the receipt and looked up the main breaker.

 

That's good an RCBO, one box checked.

 

The instructions for your Square-D / Schneider board should show the MEN connection, question is, did your sparks follow them? (if so I'd be expecting a much lower N-E voltage).

 

Sadly just looking at the meter can't tell us what tariff you're on.

 

Also, depending upon your inspector a 63A incomer on a 15/45 may attract a comment.

 

Thanks Crossy, you're giving me invaluable information.

 

Tomorrow I am meeting the electrician at the job site. It's for a final review/inspection, and then he'll want payment.

 

I messaged him earlier today about the N-E readings.. He just said, "I'll be there tomorrow and everything will be fixed".

 

Will the PEA inspector want to physically see the earth rod? Like I said, it's below the breaker box, inside the house. The builder was wanting to tile over it today. Like I said, I never saw anything like this before:

 

 

 

I have a picture of the breaker box now too:

 

 

This picture was taken before the main was run to the meter (2 days ago).

 

 

 

 

23 minutes ago, bankruatsteve said:

You should measure the voltage in the breaker box.  Plugging probes into an outlet is dodgy at best.

 

Thanks, I'll do that tomorrow morning when I go back.

 

 

7 minutes ago, Thomas72 said:

Will the PEA inspector want to physically see the earth rod? Like I said, it's below the breaker box, inside the house. The builder was wanting to tile over it today. Like I said, I never saw anything like this before:

 

Is the rod connected using the recommended thermic weld or a clamp? If it's thermic take a photo, if a clamp NEVER bury it.

 

Our man looked at the top of the rod, checked that the main box had the correct routing of the neutral, moaned about my 63A incomer (replaced by a 50A for the re-check although he never came back, now back to 63A) and spent 30 mins gassing with Wifey.

 

We need to see how the real incoming wiring is routed, the inspector will be looking for it.

 

22 minutes ago, Thomas72 said:

This picture was taken before the main was run to the meter (2 days ago).

 

I see a couple of worrying (not green) wires on the earth bar, I don't see a nice fat (>10mm²) wire going to the rod.

1 hour ago, Thomas72 said:

The electrician installed a 3 meter earth rod right below the breaker box. They drilled through the slab. I never saw anything like that before.

 

I did mine the same way, I drilled and tapped in a 10' copper coated rod (ostensibly to shorten the path to earth as my CU is located in, what is now, the middle of the main house).

 

The two downsides to this approach:

1. The soil below the slab may dry out giving a copper earth-ground stake less conductivity all year round
2. A direct lightning strike to your electrical system will charge the floor tile

1 hour ago, Crossy said:

 

I see a couple of worrying (not green) wires on the earth bar, I don't see a nice fat (>10mm²) wire going to the rod.

 

This photo was taken before the earth rod was installed.

 

Is there anything on the earth bar I can test with a meter?

 

1 hour ago, RichCor said:

I did mine the same way, I drilled and tapped in a 10' copper coated rod (ostensibly to shorten the path to earth as my CU is located in, what is now, the middle of the main house).

 

The two downsides to this approach:

1. The soil below the slab may dry out giving a copper earth-ground stake less conductivity all year round
2. A direct lightning strike to your electrical system will charge the floor tile

 

Yes, I've been told by others that the rod should be installed in moist soil. It's a concern.

 

I've heard the floor tile / lightning thing. Are there any real examples of that (not urban legends)? My tile is ceramic. I know we're talking about lightning, but ceramic is an insulator.

 

10 hours ago, Thomas72 said:

Is there anything on the earth bar I can test with a meter?

 

Not really, it would be useful to know where those black and grey wires go and why they're not green/yellow. Your man seems to have been pretty good on the colours front except for these two.

 

10 hours ago, Thomas72 said:

Yes, I've been told by others that the rod should be installed in moist soil. It's a concern.

 

In reality the ground under your house is unlikely to get that dry unless you're on sand. If worried you could bond the building steel (re-bar) to the rod as well. Google Ufer ground or concrete encased electrode - I understand these are very common in the US. 

 

10 hours ago, Thomas72 said:

I've heard the floor tile / lightning thing. Are there any real examples of that (not urban legends)? My tile is ceramic. I know we're talking about lightning, but ceramic is an insulator.

 

Bonding the building steel to your rod would also mitigate the (very small) possibility of side-strikes, you would effectively be sitting in a metal box (just like your car) and everything, including you, would go up and down in potential together. Ceramic is indeed an insulator, so is air and the lightning has come through 20,000 feet of that, 1/4" of ceramic would be no barrier.

 

Whilst we are talking about lightning, I would definitely consider the installation of lightning surge-protection. You should be able to get modules that fit in your board, or add a small box next to the board if there's not room.

 

looking at the diagram Crossy posted, is the incoming neutral really supposed to connect to the ground/earth?

39 minutes ago, rwill said:

looking at the diagram Crossy posted, is the incoming neutral really supposed to connect to the ground/earth?

Yes.  MEN in Thailand.

Thanks for all the help.

 

The electrician got the the site before me this morning. I think he did something. When I arrived, he was testing with his meter and he was reading 0 volts N-E at various sockets. We opened up the breaker box, tested N-E, again 0 volts. I used my meter, same readings everywhere. I could not duplicate the readings I took yesterday.

 

I showed him the diagram Crossy posted, we went through everything. He agreed with the diagram and said that's how he always does it. I verified as much as I could.

 

Regarding the earth rod, we're going to enclose (cover) it with a 5" PVC pipe with a removeable cap. Then tile around the pipe. It will keep it accessible and kind of enclose it.

 

I like the idea of bonding the earth rod to the building steel, but I'm not sure that's an easy option now. Everything has been cemented over. The nearest exposed steel is the interior roofing above the second floor.

 

I think my electrician is pretty knowledgeable and not prone to cutting corners. We have well water. I will be adding a filter, storage tank, then a second pressure pump. I was talking with him about it. The current well pump is on it's own breaker at the pump. He's enclosing it nicely and asked me to go pick up another earth rod, which he'll install at the pump breaker. My guess is, because this part of the electrical is isolated from the main breaker box, he wanted to make sure it was properly grounded.

 

 

 

 

If you now have 0V (or near) N-E and it's wired like the diagram you're good to go.

 

Do consider lightning surge supression.

 

Our pumps all have local rods and are on 2-core cable with RCBOs at the source end.

20 hours ago, Thomas72 said:

Will the PEA inspector want to physically see the earth rod? Like I said, it's below the breaker box, inside the house. The builder was wanting to tile over it today. Like I said, I never saw anything like this before:

Correct and until he passes the electric is safe then,  they installed a new meter and refunded what was left of 10,000 baht deposit after the building was complete I think from memory  it is only then you get a customer acc number.

Just now, brianthainess said:

Correct and until he passes the electric is safe then,  they installed a new meter and refunded what was left of 10,000 baht deposit after the building was complete I think from memory  it is only then you get a customer acc number.

 

It cost me 6000 baht to install the meter. No deposit. I just pulled the last bill and did the math, the rate is 7.16 baht per unit. Doing the same math on the last bill in our current (rental) house, we're paying 4.29 baht per unit.

 

The wife says she needs to go get the house book first, then go down to PEA. Hopefully it will all be done early next week.

6 minutes ago, Thomas72 said:

 

It cost me 6000 baht to install the meter. No deposit. I just pulled the last bill and did the math, the rate is 7.16 baht per unit. Doing the same math on the last bill in our current (rental) house, we're paying 4.29 baht per unit.

 

The wife says she needs to go get the house book first, then go down to PEA. Hopefully it will all be done early next week.

 

Yeah, that's a construction supply. 

 

Once you have the house book your good lady can ask PEA to switch you to the normal rate. The local PEA office will send a man to "inspect" your installation. I don't think you will have a problem other than maybe a comment about that 63A incomer (which could be resolved with a little "tea money").

 

Once the man has gone away happy you will be switched to the regular tariff (they didn't replace our meter).

 

IIRC they refunded all meter deposits earlier this year so you may be in for a nice surprise.

19 minutes ago, Crossy said:

Do consider lightning surge supression.

 

I want to do this, if for nothing else than to protect electronic devices.

 

Crossy, I think you're talking about something like this? :

 

https://www.se.com/us/en/product-range-presentation/64328-square-d-qo250pspd-qo-plug-on-neutral-whole-home-spd/?parent-subcategory-id=54825&filter=business-4-low-voltage-products-and-systems

 

Our breaker box is full. I'd have to add a second box then chain it?

 

 

The Square-d chap is the right kind of thing but you can't use the US version which is intended for 120-0-120 supplies.

 

If you're going to need a second box getting a DIN mount box and arrestors would be cheaper and more readily available.

 

If you can rationalise your breakers and free up one slot, this should just plug right in 

https://www.lazada.co.th/products/square-d-surge-protection-device-qospd20-schneider-electric-i821108205-s1682116905.html

 

33 minutes ago, Thomas72 said:

 

It cost me 6000 baht to install the meter. No deposit. I just pulled the last bill and did the math, the rate is 7.16 baht per unit. Doing the same math on the last bill in our current (rental) house, we're paying 4.29 baht per unit.

 

The wife says she needs to go get the house book first, then go down to PEA. Hopefully it will all be done early next week.

Your wife is correct they need the blue book for the address then i believe you will get another meter, sounds like your still paying building rate 6,000 for a meter is way to much do you have the receipt for the 6,000 i still think it was a deposit though, to pay for electric when building, so the builder can't do a runner. do you have a customer/account num yet ?

28 minutes ago, Crossy said:

 

Yeah, that's a construction supply. 

 

Once you have the house book your good lady can ask PEA to switch you to the normal rate. The local PEA office will send a man to "inspect" your installation. I don't think you will have a problem other than maybe a comment about that 63A incomer (which could be resolved with a little "tea money").

 

Once the man has gone away happy you will be switched to the regular tariff (they didn't replace our meter).

 

IIRC they refunded all meter deposits earlier this year so you may be in for a nice surprise.

Had mine refunded 3 or4  yrs ago.