Location of ground rod, how deep in ground, type of ground rod, where to buy, how long/material (copper?)

[DineshR]

Hello,

 

I am looking for some quick guidance on where to locate the ground rod for electric power to a house I am building.

 

I have attached a drawing of the house layout and would appreciate some guidance on the following.

 

1. The utility power pole is located about 20 meters from the house and the electric wire will be run overhead from that pole to the house roof top area.

2. The main circuit breaker panel box will be located in the kitchen area as shown. (only a single phase will be used)

 

So my questions are :

 

- Should the ground rod be located in the kitchen below the main circuit breaker panel box ? Or if not, where is the ideal location ?

 

- Is this ground rod a copper rod, how long deep should it go into the ground (or can it be cast into the concrete foundation) ?

 

- Where can I buy such a rod and approx how much does it cost ?

 

- How is the rod connected to the breaker box ?

 

- Or can the ground rod be installed AFTER the house is completed ?

 

Your advice would be much appreciated. Thanks in advance.

 

[sometimewoodworker]

21 minutes ago, DineshR said:

 

- Should the ground rod be located in the kitchen below the main circuit breaker panel box ? Or if not, where is the ideal location ?

A) You can. But the PEA may want to see it. 
B) a place near the house that is always damp.

21 minutes ago, DineshR said:

- Is this ground rod a copper rod, how long deep should it go into the ground

Not copper but copper coated steel. 2.5 meters is usual, if it will go in, a bit shorter is OK if the longer you will use 1 connected to another.

21 minutes ago, DineshR said:

or can it be cast into the concrete foundation

You can/should connect the house steel work but the PEA may want to see the ground rod.

 

21 minutes ago, DineshR said:

- Where can I buy such a rod

Every electrical supplier and Global House, DoHome, Thai Watsadu, HomeHub, HomePro etc.

 

21 minutes ago, DineshR said:

approx how much does it cost ?

 

Not much, under 2,000

21 minutes ago, DineshR said:

How is the rod connected to the breaker box ?

16mm square copper cable, or 10mm

Edited November 11, 2020 by sometimewoodworker

[CrunchWrapSupreme]

Make sure the hot water heater for your shower is well connected to this rod. Check with a continuity tester. You may have a shocking experience in the morning.

[Crossy]

STWW got all the major points.

 

You may find this PEA document useful for your sparks Groundwire Mk2 book-Manual.pdf

 

The important diagram with translations.

 

[carlyai]

Make sure the rod and connection will remain visible after cementing and tiling. They tend to hid rods over here.

[DineshR]

All. Thank you so much for the quick inputs.

 

@Crossy You show a ground bus bar and it shows that the incoming neutral and the ground rod are connected electrically (meaning shorted) via this ground bus bar - is this what you meant by the drawing or am I mis-interpreting the drawing ? And I presume that the sub circuit breakers can also be RCBO's ?

 

Please advise. Thanks.

[Crossy]

Yes, the incoming neutral must be routed via the ground bar, it's the Thai implementation of MEN and your inspector will look for it.

 

Yes, there's no reason why you can't have a main MCB and individual RCBOs (other than cost).

 

[DineshR]

@CrossySo would having the main breaker be an RCBO(or RCD) and the remaining sub breakers be non RCBO(or RCD) be the lower cost solution with no disadvantages ?

 

Or would have a non RCBO main breaker with RCBO sub breakers be a more safer implementation ? Just curious.

[Crossy]

One RCBO on the front end is fine, except that when it goes off the whole house gets plunged into darkess (and your freezer starts to warm up).

 

A split-board (with two RCDs) is a happy medium if you put half the lights and outlets on one RCD and half on the other.

 

It's also worth having an unprotected (just an MCB) outlet for your freezer (wouldn't be allowed now in the UK, but we are not in the UK).

[DineshR]

@Crossy. Thank you very much. All the comments have been very, very helpful. Much appreciated.

[SimpleMan555]

A few more items to think about in addition to the other useful comments would be:

 

1. Make sure the Earth/ground cable is in a single length going from the ground rod to the CU Neutral Bar. Some electricians here will branch it off prior to the CU.

2. The 2.4m rods can be tough to install,  a large hammer-drill placed on the top can be used with good success,  a heavy sledge hammer with short strokes also works well.

3. Ensure the Rod>Cable connections is secure, and visible for inspection throughout its service life. The connections can corrode and you can then lose your Earth/Ground protection.

Cheers!

[DineshR]

@SimpleMan555Thank you. I did buy the ground rod (2.4 M was only 200 baht interestingly) and had the electrician install it. He drove it into the ground using a hammer but it took him a while to get it in all the way. He then connected it with a single length cable (size #10) and ran it under the slab before the slab was poured. The cable was laid inside a yellow pipe. The cable was simply connected to the rod using the screw/clamp that came with the rod. The wire was wired tight around the rod and then the screw/clamp was used to tighten it against the rod. I asked him to leave the top of the rod and the wire/rod connection exposed just under the ground.

[Crossy]

1 hour ago, DineshR said:

I asked him to leave the top of the rod and the wire/rod connection exposed just under the ground.

 

Is it actually buried?? If so it will corrode very rapidly. 

 

Give it an enclosure (one of the floor drain access covers would do) to keep the soil / damp off it.

[simon43]

I use many copper earth rods in my garden for ground connections for my amateur radio antenna ground radials.  It's a good idea to coat the wire/rod connection with thick grease to minimise the corrosion.

[DineshR]

@simon43Thank you for the suggestion. Will do as you suggest.

@CrossyThe rod is actually buried and the top part is covered with earth. I will remove it and cover it with something to keep the dirt off it. But if you say that it will corrode rapidly, won't the copper rod deep in the ground corrode as well ? Or are you saying only the part of the rod that is connected to the wire will corrode if it is exposed to the earth / dampness ? Please advise. Thanks.

[Crossy]

13 minutes ago, DineshR said:

The rod is actually buried and the top part is covered with earth. I will remove it and cover it with something to keep the dirt off it. But if you say that it will corrode rapidly, won't the copper rod deep in the ground corrode as well ? Or are you saying only the part of the rod that is connected to the wire will corrode if it is exposed to the earth / dampness ? Please advise. Thanks.

 

Time to get out your High School chemistry books.

 

Corrosion (oxidation) needs moisture and oxygen.

• Deep in the ground there is plenty of moisture but little oxygen = no oxidation.
• In the air there is plenty of oxygen but not really much moisture = no oxidation.
• At the air/ground interface there's plenty of both = oxidation.

We are not aided by the fact that copper oxide is not a particularly good conductor of electricity so if the joint between the copper rod and the copper wire gets oxidised then your earth is compromised.

 

On the plus side, copper (like aluminium) creates a thin oxide layer which then prevents further oxidation (the green colour that copper roofs go is copper oxide) so the bit of the rod itself that's in the airy/damp region just gets surface corrosion then stops.

 

[DineshR]

@CrossyThe high school chemistry lesson was useful. I understand. Thank you.

[Crossy]

1 minute ago, DineshR said:

@CrossyThe high school chemistry lesson was useful. I understand. Thank you.

 

The scary thing is that I remember it (long, long ago) but I forget what I had for breakfast ????

 

[sometimewoodworker]

1 hour ago, Crossy said:

 

The scary thing is that I remember it (long, long ago) but I forget what I had for breakfast ????

 

That’s one better than me as I forget if I had breakfast or (other meals) not until I get the hunger shakes that tells me I didn’t. 

[DineshR]

@Crossy I took a couple of photos to show where exactly the ground rod is relative to the earth level - it's just below the earth line. After construction, I will be adding some more earth so the ground rod may be a couple of inches below the ground. Right now, I've just cleared the earth around the ground rod and placed a plastic shield around it as you can see. Given where it is currently, can I just cover it completely with earth as it then won't be exposed to the air - though it will get damp if it rains - but then due to the lack of oxygen, it won't oxidize even when it's damp. Or can I simply cover the whole thing in concrete and not worry about it at all ? Please advise.

[impulse]

20 hours ago, Crossy said:

Time to get out your High School chemistry books.

 

Corrosion (oxidation) needs moisture and oxygen.

 

Chemistry is great, but when you introduce electrical currents from an external source, all bets are off.  

 

In fact, the basis of chemically driven corrosion is electrical voltages that can be orders of magnitude lower than an external source.

 

On an aside, there are some great YouTubes done by guys that install ground rods that actually have to be electrically tested as opposed to just a visual inspection according to a cookbook.  It's scary how deep they often have to go to get an adequate path to ground.  On the order of 10+ meters in many cases.

 

Edited November 16, 2020 by impulse

[Crossy]

33 minutes ago, DineshR said:

Please advise.

 

Get your contractor to do it properly!

 

If you really want to bury and forget then use one of the thermic-weld (Thermite) kits from your local electrical specialist, since it's outside the pyrotechnics won't be a problem (it's fun too). You may even score by simply cleaning off all the soil and using the kit on what you have. The results don't look particularly nice but if you are burying it ...

 

These welds are actually the method recommended by PEA for buried connections. Have a look at this PEA document.

 

Groundwire Mk2 book-Manual.pdf

 

Page 22 (Page 11 of the .pdf) shows the thermite in action, show that to your contractor so he knows what you want.

 

Personally, I put a ring-crimp on the end of the wire (I solder them too for added security), slip a length of adhesive-lined heatshrink over and then bolt to the rod. A spray of "cold galvanising" will fill up any remaining air spaces and protect everything. Add a bit of PVC pipe (left over from the toilet plumbing) with a cover so you can inspect it.

 

[sometimewoodworker]

1 minute ago, Crossy said:

Add a bit of PVC pipe (left over from the toilet plumbing) with a cover so you can inspect it.

You probably want a 6” x 3” or 4” diameter  pipe section to be sure it doesn’t get filled with water or earth. Otherwise it will encourage corrosion, the  exact thing you’re trying to avoid

[Crossy]

1 minute ago, sometimewoodworker said:

You probably want a 6” x 3” or 4” diameter  pipe section to be sure it doesn’t get filled with water or earth. Otherwise it will encourage corrosion, the  exact thing you’re trying to avoid

 

Yeah, ours is actually in a "spare" concrete drain pit about 18" x 12" x 10" deep with the cover tiled over (removably of course). 

[DineshR]

Thank you all for the suggestions.  I will be speaking with the contractor tomorrow together with the PEA handbook and then decide what we'll do. Thanks again.