Earthing An Aircon Unit

[jubby]

I've just installed a Safety-cut, RCB, consumer unit and am in the process of upgrading a lot of the wiring where earth should be fitted.

I'm just checking out one of the Aircon units, its a metal casing so no doubt should have an earth strap. I checked the casing with an electricians screw driver and there was a light indicating some voltage which surprised me. I need a new battery for the multimeter to test the actual current, but in the meantime Is it normal to have a voltage here, I would have said not but sometimes get a shock from the computer casing also. I don't want to connect an earth strap until I check it out with someone. I would have thought it would trip the elcb and be a fault.

The aircon works fine without the earth but I'd consider it dangerous.

advice anyone please

[Crossy]

Your aircon should definately be grounded, that you are seeing some voltage with your neon suggests that it is not.

In itself some leakage is not an issue, computers do it all the time, older motors tend to leak somewhat. Do check the current to a good ground, if it's less than a couple of milliamps there is no problem and your Saf-T-Cut won't trip, if it's much more then there is a fault that needs investigating. The neon will light at a few microamps so you may not even be able to measure the leakage with a meter. The ELCB will only trip when there is >30mA flowing to ground.

It's acceptable to put your aircon, freezer and indoor overhead lights on circuits that are not ELCB protected (via a split-service consumer unit http://www.crossy.co.uk/wiring/Consumer.html ) provided they are correctly grounded there is no hazard. The idea being that it reduces the possibility of nuisance trips so you don't come home to a freezer full of penicillin and your lights stay on if there is an emergency (fire).

If you're getting a tingle from your PC check that it really is grounded, the leakage is via the inlet filter capacitors and is not a fault. The filter needs the ground to work properly, so even if it's not biting a desktop PC should be grounded.

[lopburi3]

Most Thai do not place air conditioners on Safe-T-Cut circuit so that might be a factor. But make sure that the Safe-T-Cut is not in bypass mode while you have it on your mind.

[jubby]

The Aircons was connected via a local MCCB straight to the Clock on the Post. They bypassed both the crocodile type switch and the only other MCCB device I had for the rest of the house. I've put a crocodile clamp type switch between it and the clock at present. I was just wondering wether to connect it straight to the new RCB & distribution unit or leave it on its existing MCCB. I've just checked the cabling further and the cable from the Aircon Head unit has the brown, blue and earth that I'm familiar with in the uk. The earths cut off and the MCCB is feeding the Blue (neutral) with LIVE. I think this is whats called reverse polarity (The Thai electricians I've had the pleasure to know don't seem to be familiar with the term or indeed care). I think a simple solution would be to correct the live feed and connect the earth from both the inside & outside units to there own copper grounding rod.

what do you think ?

[Crossy]

Sounds like a typical Thai job

OK.

As a minimum you should correct the polarity and ground the aircon units.

You should consider sorting the job properly, something akin to the split-service consumer unit on my website (see my last post) would do the trick. Keep the aircons on the un-protected side of the ELCB along with your freezer and some lights.

You could get a second CU, feed the incoming supply to it and then feed your Saf-T-Cut from the switched rails inside (to ensure you have a single isolator that will kill all power). From the Saf-T-Cut go to your existing CU. This will work like a split service CU without costing too much.

While you're at it get a decent ground spike and connect it to the ground bar in the CU, link all your grounds from outlets and aircon etc. to this ground bar.

[Cuban]

I've just checked the cabling further and the cable from the Aircon Head unit has the brown, blue and earth that I'm familiar with in the uk

It is wise to assume that the person that carried out the original wiring in almost any situation in Thailand is color-blind, has no formal training and is at least partly homicidal.

Using these thoughts as a baseline when working of other people's wiring means I am in the habit of not assuming that color codes will be followed etc. In the office where I have had cause to look inside the odd socket I have found missing earths (not surprised) and supply wires twisted together where a connection block should have been used. Having seen many bad examples of wiring here I must confess I am still learning and a little surprised by the ways that they can get it wrong do it the Thai way. Last week I discovered that only half the wall sockets are feed through 'our' electric meter and isolator, the rest are fed via the company next door's supply! TiT

[Crossy]

It is wise to assume that the person that carried out the original wiring in almost any situation in Thailand is color-blind, has no formal training and is at least partly homicidal.

Using these thoughts as a baseline when working of other people's wiring means I am in the habit of not assuming that color codes will be followed etc.

An excellent point Cuban, wish I'd thought of it.

I wonder how many of next doors' outlets are connected through your meter

[jubby]

Thanks for the help & tips Guys. Good point about keeping the freezer off the RCB. I'm just going to take on a few sockets/outlets per day and see how it goes. The Thai wiring is definately interesting to say the least. A friend says its just that the thai system is at a higher level of understanding than I'm used to. ;-)