Earthing/grounding A Light Switch?

[wpcoe]

I finally got around to earthing the outlet that my computer equipment plugs into. How nice not to get little tingles when I brush against things!

Originally I was simply going to run an earth wire from a three-prong adapter in the existing two-prong outlet up to the consumer unit (this is a rented townhouse), but I decided to just replace the two pin double socket with a real three-pin grounded double socket. I couldn't do it as cleanly/neatly as I wanted. The outlet is about 50cm from the consumer unit and between the outlet and the box is a two-switch box and a covered track over the wires:

Unfortunately I wasn't able to run the new earth wire concealed under the track. No matter how I tried I couldn't get more than half way through the pathway under the track, so I now have an exposed green earth wire to the right of it, as you can see.

I ran the earth wire through the switches' box and found that none of the wires are secured to the switches. There are no screw terminals on the switches, just the holes in the back where you stab the stripped bare wires into. However, whatever gauge wire those holes are meant for (14g?) the wires used are way thinner and don't grip and just slide in/out of the holes. Putting the switches back in without having at least one of the wires slide out was tricky, and I'm not at ALL comfortable with that arrangement, so I will be replacing the switches with ones with screw terminals.

All of that as a preface to my question: If I run an earth wire from the new switch to the earth bar in my consumer unit, does that earth the actual light fixtures, as well? If earthing the switches earths the entire two light circuits, I'll do it. If the earth wire has to actually tie into the light fixtures themselves, that's probably not going to happen.

The electrical box for the outlets is recessed into the rendered brick wall, but so close to the vertical support beam, that in order to place the cover plate on, they had to chisel out of the support beam to provide space for about 1/4" of the right side of the cover plate. My new fixture's plate is thicker and therefore couldn't fit into that chiseled slice, so I had to cut off 1/4" of the new plate. Plan ahead? Why bother! And they had thoughtfully siliconed into the chiseled gap, so it was a bit of a process to even get the original cover plate off.

The wiring in the consumer unit is professional:

-- wires neatly bundled (although a stricter color coding scheme would have been better), and earth wires (one black large gauge) running to an earth spike in one direction, and (I think) the white thick one to the metal roof rafters in another direction. (It leads out of the unit from the earth bar and it appears to head up the wall through the floor and up the upstairs wall into the attic space, so I'm just guessing it's attached to the metal framing. My ample body size is not compatible with the entry hatch in the bathroom ceiling to actually enter the attic space.) Prior to today's adventure, the only things connected to the earth bar were two water heaters, the outlet for the washing machine, and the water pump.

The wiring within the switch and outlet boxes appears to have been done by somebody else.

[Crossy]

Well done for adding to the safety of your installation

You should also add RCD protection, a front end Safe-T-Cut would probably be the easiest route, or add RCBOs to your water heaters and any wet area outlets.

No, earthing the switch won't earth the fittings, but if they are out of reach it's not a critical issue.

Do replace that switch with loose wires.

[cooked]

You have an earthing spike? Wow! I have a rusty nail attached by apiece of fencing wire into the concrete patio. I do have a safe T Cut though.

[lopburi3]

Unfortunately I wasn't able to run the new earth wire concealed under the track. No matter how I tried I couldn't get more than half way through the pathway under the track, so I now have an exposed green earth wire to the right of it, as you can see.

The track (plastic conduit) is two piece so just pry the cover (lift at one end and should snap right off) off and then you can run the green wire in it and replace the cover. Perhaps do when you replace the switch.

[electau]

You do not earth a switch, you earth the enclosure if metallic. The light fitting should be earthed but in Thailand if the fitting is out of arms reach from where it may be reasonably accessed ( eg from floor level) earthing is not required.However the circuit should have RCD/RCBO protection.

[wpcoe]

Well done for adding to the safety of your installation

You should also add RCD protection, a front end Safe-T-Cut would probably be the easiest route, or add RCBOs to your water heaters and any wet area outlets.

No, earthing the switch won't earth the fittings, but if they are out of reach it's not a critical issue.

Do replace that switch with loose wires.

Thanks for the back pat. Coming from you, that's taken as high praise!

On the home project list is additional electrical circuit protection. I get all tangled up with the terms: RCD/RCBO/RCCB/GFCI/etc. What I want is the device to replace individual circuit breakers in the consumer unit. That's an RCBO isn't it? I thought that RCBO = CB + RCD protection, no? Googling the terms confuses me as apparently they are somewhat interchangeable and/or not consistently used?

In my consumer box, there are nine Chang brand CBs, one double, and eight singles.

The double one says "C50, 240/415V, 10,000."

The singles are (2@):

"C16, 240/415V, 6000"

"C10, 240/415V, 6000"

"C32, 240/415V, 6000"

"C20, 240/415V, 6000"

To replace them with (what I think are ) RCBOs, what specifically do I look for? If it's not a boatload of money, I'd replace all of the singles. If I replace all the singles, I wouldn't need to replace the double, main breaker, would I?

I already replaced the two light switches with nicer looking ones. Wires are securely attached now. I couldn't even find grounded light switches at HomePro, so it's a good thing I wasn't hell bent on grounding them.

You have an earthing spike? Wow! I have a rusty nail attached by apiece of fencing wire into the concrete patio. I do have a safe T Cut though.

I'm assuming there is a ground stake under a tiled part of the garage floor. I can follow a thick wire from the earth bar, through the front wall, down a beam until the point where it disappears behind render and ceramic wall tiles. A few feet from the beam is a section of floor tiles that looks like it somehow can be lifted up, but I haven't found a way to lift it.

The track (plastic conduit) is two piece so just pry the cover (lift at one end and should snap right off) off and then you can run the green wire in it and replace the cover. Perhaps do when you replace the switch.

Thanks, I didn't know they were two-piece like that. However, they siliconed the entire length and across the top and bottom of the track, so rather than deal with that, I just bought a new track to cover the single green ground wire running next to it.

You do not earth a switch, you earth the enclosure if metallic. The light fitting should be earthed but in Thailand if the fitting is out of arms reach from where it may be reasonably accessed ( eg from floor level) earthing is not required.However the circuit should have RCD/RCBO protection.

Thanks for helping clear that up . As mentioned, I couldn't even find a grounded light switch today. The lights fixtures are flat against the ceiling three meters above the floor. They shall remain un-earthed. If this were my own home, I'd probably have the entire house rewired to earth everything, but as a rental, I'm going to restrain myself.

[Crossy]

On the home project list is additional electrical circuit protection. I get all tangled up with the terms: RCD/RCBO/RCCB/GFCI/etc. What I want is the device to replace individual circuit breakers in the consumer unit. That's an RCBO isn't it? I thought that RCBO = CB + RCD protection, no? Googling the terms confuses me as apparently they are somewhat interchangeable and/or not consistently used?

Yes, a device that provides overcurrent and earth leakage protection is an an RCBO. Part of the issue is that Thaivisa is a multi-national community and differing terms are in use in different countries.

In my consumer box, there are nine Chang brand CBs, one double, and eight singles.

The double one says "C50, 240/415V, 10,000."

The singles are (2@):

"C16, 240/415V, 6000"

"C10, 240/415V, 6000"

"C32, 240/415V, 6000"

"C20, 240/415V, 6000"

To replace them with (what I think are ) RCBOs, what specifically do I look for? If it's not a boatload of money, I'd replace all of the singles. If I replace all the singles, I wouldn't need to replace the double, main breaker, would I?

That consumer unit looks like it accepts plug-in breakers. I think that Square-D single width RCBOs will fit, take one of your breakers along to your local electrical outlet to ensure they will fit. Look for current ratings the same as your breakers and leakage trip levels of 30mA.

To use individual RCBOs you need to identify the neutral associated with each circuit and pass it back through the RCBO on its way to the neutral bar (RCBO has a tail to connect to the neutral bar), any crossed or borrowed neutrals are going to give you headaches.

This thread may be of interest

[electau]

MCBs. C. frame (standard) current rating in amps (16). 6000 short circuit capacity in amps.

These are the IEC ratings for a protective device.

RCBOs have as above but with the residual current for earth faults, 10mA and 30mA.

Main switch 50A C frame 10000A short circuit capacity.

Do not replace the main switch (MCB).

Edited November 20, 2012 by electau

[lopburi3]

If all circuits are to be protected a simple replacement of the "The double one says "C50, 240/415V, 10,000." with an RCBO is likely the easy and cheapest option.

[wpcoe]

Crossy/electau/lopburi3: Many thanks for your input!

I've read that the "negative" about replacing the main CB is that if any individual circuit trips, the entire house goes dark. I'm not sure that would bother me. It would be "nice" to just have a single circuit cut off, but I want to see how much money we're talking here. As a rental, I'm not really wanting to spend a lot of money. If replacing all 8 single CBs is cheap enough, I'll do it. If it seems pricey, and just replacing the double, main CB is reasonable, I'll do that.

Another thing lurking in my mind -- and this might lead me to simply buy the hardware and have an electrician do the installation -- how do I remove all the power from the consumer unit? When working on a single circuit to replace outlets & switches, I switched off the main (double) CB. Overkill, I know, in that the individual CB for the circuit involved should have been adequate. BUT, when actually removing CBs -- and especially the main (double) CB -- how do I protect myself? I might be in over my head here? I don't even own rubber flip flops any more.

[Crossy]

For working inside the CU with the exception of the incoming supply, just open the main breaker. Remember that the hot terminals of the incomer are still hot.

If you want to replace the main breaker, get a local sparks to do it.

I did replace my incomer whilst still live, but I would never recommend a DIYer to do that, it's just too risky. There is not just the risk of zapping yourself, but also, if you do manage to short L-E or L-N there is no protective device (fuse) to open and many thousands of amps can flow with explosive consequences.

[doglover]

The "negative" ,wpcoe, is correct. But is really not all that bothersome. My main breaker is an adjustable RCBO from safe-t-cut which can be set to trip at 5, 15, 25 or 30 mA's leakage. Day in day out I have it set at 5mA and the fridge and airconditioners run without issue. When it rains sideways some of the exterior lights were mounted with no sort of seal and will trip the main. I find a flashlight crank the setting up to 15mA and it usually holds. When I use the oven I crank it up to 30mA. If the main still trips on the highest setting you can just flip all the individual breakers off, flip the main back on and then flip each individual circuit on until you find the culprit until what you suspect is causing the leak has passed and re-energize. Your panel may not accomodate a multi-setting RCBO but you could still just replace it with a 30mA hard set as suggested.

If you decide to go with the individual circuit RCBO's you will need to know how to identify the wire pairs correctly, as mentioned. But if you decide to tackle that you can always swap out your pricey individual RCBO's with the originals when you decide to cease renting at that residence and take them with you.

[electau]

With one RCBO protecting the whole electrical installation you may experience nuisance tripping due to excessive leakage current. An RCD device is designed to trip at between 50% and 100% of the rated current ( or the current setting in mA if a selectivity switch is fitted). 10ma and 30mA are the IEC ratings.

The Main switch (MCB) isolates the whole installation for the purposes of safety.

In Thailand there is NO provision for service protective devices eg HRC fuse to protect the consumers mains and metering. This is for fault currect limiting ( short circuit protection) and an isolation point to disconnect the electrical installation. They are not for overload protection.