Sparky Help

[happyrobert]

Any PROFESSIONAL sparkies out there who are knowledgable about the following?

My building site has about a foot of soil, then nothing but granite. Little chance of driving a 3 meter (if I can even find one) copper rod in the ground for grounding purposes.

So, I remember some builders using the rebar in the concrete slab as the ground.

Anyone have real experience with this?

BTW, exothermic welds in Trad? Then, what would I use to attach the ground wire to the rebar?

Thanks in advance.

[InterestedObserver]

Although you seem to have little choice, rebar in concrete is not ideal when sitting on a granite base. Exothermic welds can be used with grounding stakes, at least when I did my last ground grid, although when dealing with rebar, grounding clamps are normally used. What are your grounding concerns - touch potentials (safety), IT signal grounding or lightning protection?

Edited July 18, 2011 by InterestedObserver

[happyrobert]

Although you seem to have little choice, rebar in concrete is not ideal when sitting on a granite base. Exothermic welds can be used with grounding stakes, at least when I did my last ground grid, although when dealing with rebar grounding clamps are normally used. What are your grounding concerns - touch potentials (safety), IT signal grounding or lightning protection?

Primary concern is not becoming another shower thread on Thai Visa.

Secondary concern is electronics safety in a lightning prone area.

[InterestedObserver]

Given that you cannot use ground rods, lay copper ground cables in your building footings. Connect them together at one central location, such as the electrical distribution panel ground. That's the best you can do.

[happyrobert]

Given that you cannot use ground rods, lay copper ground cables in your building footings. Connect them together at one central location, such as the electrical distribution panel ground. That's the best you can do.

Yeah, better than rebar. Thanks!

[InterestedObserver]

Given that you cannot use ground rods, lay copper ground cables in your building footings. Connect them together at one central location, such as the electrical distribution panel ground. That's the best you can do.

Yeah, better than rebar. Thanks!

I should have added, pour the concrete around (in contact with) the bare ground cables.

Edited July 18, 2011 by InterestedObserver

[Crossy]

A lot of variables determine how good a ground you can get with your structural steel, it's only relatively recently that the UK prohibited its use so it can't have been that bad. Problem is of course that unless you have the relevant test gear you really don't know how good a ground you have

I'd be tempted to install a 1m x 1m ground grid of galvanised (hot-dipped) bar or pipe protected where it's been welded and at the cut ends with a bitumen based product and buried as deep as you can get it. If you can get some coal or bentonite they are both ground enhancers so bung them in the hole too.

The above is probably overkill in a domestic situation, but you can never have too good a ground and the cost should be minimal.

Use a regular ground rod clamp to make the connection, paint it with acrylic paint and give it a lid of some sort to reduce the possibility of physical damage.

[Kwasaki]

Primary concern is not becoming another shower thread on Thai Visa.

Secondary concern is electronics safety in a lightning prone area.

Just make sure you get a good quality ECCB ( residual current circuit breaker ) wired in your be fine.

[Lancelot]

I'd be tempted to install a 1m x 1m ground grid of galvanised (hot-dipped) bar or pipe protected where it's been welded and at the cut ends with a bitumen based product and buried as deep as you can get it. If you can get some coal or bentonite they are both ground enhancers so bung them in the hole too.

The above is probably overkill in a domestic situation, but you can never have too good a ground and the cost should be minimal.

If it were me, I'd do as Crossy has recommended. The wire grid placed as close as possible to the bedrock should do the job

[Crossy]

How about an Ufer ground or concrete encased electrode? http://en.wikipedia.org/wiki/Ufer_Ground

From here:- http://www.iaei.org/magazine/2001/07/concrete-encased-electrodes-and-the-grounding-electrode-system/

( c ) Concrete-Encased Electrode. An electrode encased by at least 2 in. (50.8 mm) of concrete, located within and near the bottom of a concrete foundation or footing that is in direct contact with the earth, consisting of at least 20 ft (6.1 m) of one or more bare or zinc galvanized or other electrically conductive coated steel reinforcing bars or rods of not less than ½-in. (12.7-mm) diameter, or consisting of at least 20 ft (6.1 m) of bare copper conductor not smaller than No. 4. Reinforcing bars shall be permitted to be bonded together by the usual steel tie wires or other effective means.

As Kwasaki notes an RCD is non-negotiable on your shower circuit.

[Lancelot]

Try googling Ufer. Tons of info there

[InterestedObserver]

Nice to see that we are finally quoting something from the US National Electrical Code (NEC). Australia, New Zealand and UK don't have a corner on the electrical code market

( c ) Concrete-Encased Electrode. An electrode encased by at least 2 in. (50.8 mm) of concrete, located within and near the bottom of a concrete foundation or footing that is in direct contact with the earth, consisting of at least 20 ft (6.1 m) of one or more bare or zinc galvanized or other electrically conductive coated steel reinforcing bars or rods of not less than ½-in. (12.7-mm) diameter, or consisting of at least 20 ft (6.1 m) of bare copper conductor not smaller than No. 4. Reinforcing bars shall be permitted to be bonded together by the usual steel tie wires or other effective means.

[happyrobert]

Good info.

Thanks very much everyone!

[mario299]

Good info.

Thanks very much everyone!

Happyrobert

Get familiar with the DIY forum, lots of great info there. Good luck.

mario299 :jap:

[happyrobert]

Good info.

Thanks very much everyone!

Happyrobert

Get familiar with the DIY forum, lots of great info there. Good luck.

mario299 :jap:

Ahh, now I see it! I did look for a forum more specific but who whoulda thunk it was a sub-forum under real estate?

[electau]

Ref AS3000.

Earth electrodes shall be of a type and shall be installed in accordance with table 5.2

Exception: conductive reinforcement of:

1. concrete foundations embedded directly in the soil; or
   
2. concrete foundations of a building or floor slab in contact with the ground and not impeded by a continuous insulating barrier, may be used in lieu of an electrode in table 5.2.
   

Edited July 24, 2011 by Crossy
fixed the list tags :)