Safety switchs

[DUNROAMIN]

Hi to all, would like to know if a safety switch (RCD) will work if you only have an earth fitted to the Circuit breaker board. Our rental house is a typical Thai house that was wired with no earth to all the outlets and breaker board. I thought there maybe something available on the market now for this problem.

Cheers

[wayned]

An RCD will work without an earth.  It monitors the current on the live and return legs and trips if there is an imbalance greater than what it is set to.  Some RCDs are fixed, but some have a dial where you can set the trip current.

[Crossy]

Spot on Wayned :)

[DUNROAMIN]

2 hours ago, wayned said:

An RCD will work without an earth.  It monitors the current on the live and return legs and trips if there is an imbalance greater than what it is set to.  Some RCDs are fixed, but some have a dial where you can set the trip current.

Hi, so tell me if I am wrong, if you have a short in an appliance or somewhere in the circuit of the house the RCD will trip and cut the power?

[Strange]

23 minutes ago, DUNROAMIN said:

Hi, so tell me if I am wrong, if you have a short in an appliance or somewhere in the circuit of the house the RCD will trip and cut the power?

 

Yes, and the RCD is WAY more sensitive than relying only on a breaker.

 

Better for humans and sensitive electronics. 

 

 

[DUNROAMIN]

2 hours ago, Strange said:

 

Yes, and the RCD is WAY more sensitive than relying only on a breaker.

 

Better for humans and sensitive electronics. 

 

 

OK thanks for that, will check some out at Thai Watsado. Then just have to find a competent electrical who knows what he is doing.

[Strange]

18 minutes ago, DUNROAMIN said:

OK thanks for that, will check some out at Thai Watsado. Then just have to find a competent electrical who knows what he is doing.

 

Is there an electrical problem in your house right now? Or is this just to add a level of safety?

 

RCD can trip pretty easy if there is a problem already and might not solve an existing issue. 

[bankruatsteve]

A "short" is normally not an earth fault and would not be detected by an RCD.  But, it would trip the over-current breaker.  If the appliance had some fault that would allow current to travel to "earth" via, for example, a person, the RCD trips.

[Strange]

14 minutes ago, Arjen said:

NO!

 

A short (so L-N connection) is not detected by an RCD. Also when a  person touches L and N a RCD will not trip, unless there is current also going to ground. When the person is "flying" RCD will never trip.

 

But there are people here with more knowledge on this subject.

 

Arjen.

 

Take it easy Nancy!

 

Of course if you go L+N the RCD will not trip and the breaker will. A short is also a short to EARTH. You can debate semantics all you want. Call it "Leakage" if you want. But an unintentional path to earth (over some electronics normal "Leakage") can still be a short. "Short" is just an unintended path of least resistance. 

 

If you short to EARTH, the breaker will still trip, if you short to NEUTRAL the breaker will still trip. The RCD just "Watches" for leakage to EARTH and trips. 

 

Residential wiring and safety is a multifaceted subject, witch is why I went on to ask the OP if there was an actual problem right now, or if this RCD was just to add a level of safety. If the OP has an appliance that has a L+N short/fault/whatever right now, and adds a RCD, won't fix or do anything. If the OP has a wiring connection in his ceiling or "Attic" space and L touches a steel support beam in his ceiling and finds a path to EARTH, the RCD will not solve the problem, but could prevent a fire. 

 

14 hours ago, Strange said:

Yes, and the RCD is WAY more sensitive than relying only on a breaker.

 

This still stands where humans are concerned. 

[DUNROAMIN]

13 hours ago, Strange said:

 

Is there an electrical problem in your house right now? Or is this just to add a level of safety?

 

RCD can trip pretty easy if there is a problem already and might not solve an existing issue. 

Hi, currently I have some major issues at the moment.  I am concerned about the wiring in this house. I have found that the circuit breaker board is wired to the neutral side of the power, if you turn a breaker off the power is stopped to an appliance, however, you still a live power wire at the outlet. If I want to replace or fix a power outlet I have to shut down the whole house.  We have a fluro light in the bedroom that will not turn off completely, it still glows a bit after switching off, stays like this for hours. Also when we having lightning close to the house our down lights come on and will not switch off, they have dimmer controls, after about 30 minutes they switch off. It seems the whole house is wired the wrong way around. We were using a power point in the kitchen when it stopped working. I found the wiring burnt out, as it had over heated from using a kettle. I was terrified to find the wiring that was used was the same cable used for the downlights in the overhead cupboards, some <deleted> so called electrician had wired the 220 outlet from the 2.5 power cable to the power outlet with 12v low voltage cable. When this happened it did not trip anything, We were lucky it did not cause a fire.

[Crossy]

27 minutes ago, Arjen said:

Ok, my shortage of knowledge (so I should not write here). I always thought that a "short" is a connection between L and N, or + and - when it is DC, without, or with a very low resistance.

 

In reality a "short" is any inadvertent connection whether it be L-N, L-E or N-E, one would normally qualify with a location "L-E short" or some such.

 

So, a L-N short won't open an RCD but it will open an MCB (over current device), it will also open an RCBO which combines the functions of both.

 

A L-E short will open an RCD (and RCBO) but it often won't open an MCB as the ground resistance limits the current to something less than the trip current of the MCB. It does not however, limit the current to less than the lethal current of 30mA or so, so without the RCD you die if it's you providing the path the earth.

 

 

[Strange]

41 minutes ago, Arjen said:

Ok, my shortage of knowledge (so I should not write here). I always thought that a "short" is a connection between L and N, or + and - when it is DC, without, or with a very low resistance.

 

Apologies

 

Arjen.

 

 

 

No apologies necessary you didn't do anything wrong. Write here all you want I don't know everything either. You were not "wrong" or anything. 

[Strange]

OK Ill do my best here:

 

3 hours ago, DUNROAMIN said:

I have found that the circuit breaker board is wired to the neutral side of the power, if you turn a breaker off the power is stopped to an appliance, however, you still a live power wire at the outlet. If I want to replace or fix a power outlet I have to shut down the whole house.

 

Are you going by the color code in the breaker panel vs wiring color at the point of use? I mean did you actually check for voltage at the outlets & appliances after the breaker opened the circuit? Not denying your situation or skill, but a lot of times over here they just wire shit up however they want in regards to color as long as its a system that they understand and can keep up with. 

 

3 hours ago, DUNROAMIN said:

We have a fluro light in the bedroom that will not turn off completely, it still glows a bit after switching off, stays like this for hours.

 

This flouresent light is a ballast/starter type? This sounds like a switch problem and I would check with the resistance of the switch in the open position and make sure its actually open or zero on the ohm meter as a first step. 

 

3 hours ago, DUNROAMIN said:

Also when we having lightning close to the house our down lights come on and will not switch off, they have dimmer controls, after about 30 minutes they switch off.

 

Dimmers are typically variable resistors and I'm inclined to think they are faulty, but its a weird situation regardless. The lights come on and won't turn off even when you twist the dimmer to the "off" position? Should be a satisfying "click" in the off position. 

 

3 hours ago, DUNROAMIN said:

I found the wiring burnt out, as it had over heated from using a kettle. I was terrified to find the wiring that was used was the same cable used for the downlights in the overhead cupboards, some <deleted> so called electrician had wired the 220 outlet from the 2.5 power cable to the power outlet with 12v low voltage cable. When this happened it did not trip anything, We were lucky it did not cause a fire.

 

Using a wire gauge that way too small turns the wire into a fuseable link and its dangerous as you found out. An RCB would not have tripped in this situation, and an RCBO probably would not have tripped in this situation either until you got a complete L-N short and this is assuming that the MCB is properly sized for a 2.5mm wire witch is a 20A breaker (I believe). 

 

Im trying to think it through, but if your L+N were backwards in your breaker panel @Crossy could he not just reverse the L+N main supply in the breaker panel? I mean there is no "Polarity" and the electronics don't know any difference, its just the way everything is switched/controlled. 

 

Anyone let me know if I'm out in left field. 

[bankruatsteve]

Yah, sounds like mains are reversed.  Maybe done wrong at the CU or could have been at the meter.  Not a rare event.

 

Assuming you have a double pole main breaker, first identify which end the mains are connected (usually the top), then turn off the breaker, and reverse the wires at the out side (usually the bottom).  

[Strange]

You can buy a cheap DVOM (Digital Volt Ohm Meter) for like 300 baht and they are good for checking voltage and resistance and switches and stuff. Wont be a Fluke but it will work.

 

Just don't try and check amperage with it even though on the dial it says you can. 

 

A non contact voltage tester is handy too for double checking outlets in your situation. Also cheap. 

 

 

[DUNROAMIN]

1 hour ago, Strange said:

OK Ill do my best here:

 

 

Are you going by the color code in the breaker panel vs wiring color at the point of use? I mean did you actually check for voltage at the outlets & appliances after the breaker opened the circuit? Not denying your situation or skill, but a lot of times over here they just wire shit up however they want in regards to color as long as its a system that they understand and can keep up with. 

 

 

This flouresent light is a ballast/starter type? This sounds like a switch problem and I would check with the resistance of the switch in the open position and make sure its actually open or zero on the ohm meter as a first step. 

 

 

Dimmers are typically variable resistors and I'm inclined to think they are faulty, but its a weird situation regardless. The lights come on and won't turn off even when you twist the dimmer to the "off" position? Should be a satisfying "click" in the off position. 

 

 

Using a wire gauge that way too small turns the wire into a fuseable link and its dangerous as you found out. An RCB would not have tripped in this situation, and an RCBO probably would not have tripped in this situation either until you got a complete L-N short and this is assuming that the MCB is properly sized for a 2.5mm wire witch is a 20A breaker (I believe). 

 

Im trying to think it through, but if your L+N were backwards in your breaker panel @Crossy could he not just reverse the L+N main supply in the breaker panel? I mean there is no "Polarity" and the electronics don't know any difference, its just the way everything is switched/controlled. 

 

Anyone let me know if I'm out in left field. 

Hi, first.

1.  I did check the power outlet after turning off the circuit breaker with a non contact mains tester, light and buzzer comes on. I don't look at the colour too much as Thailand wiring standards are a bit crazy.

2.  Yes it is the older ballast/stater type, I will check the switch to the fluro and see what I find. I''ll need to buy a basic voltage ohms meter.

3. The dimmer switches in this house have a small pilot light built  in, however I think this has been wired wrong as well, because the light is on all the time and only goes off when turned on.

4. I was thinking the same, to reverse the polarity at the board and maybe solve the problem.

 

[wayned]

It sounds that L and N are reversed at the CU,  If they are the fluro will glow as you are switching the N. It's a common indication of switching the N.  There's nothing wrong with your switch.  If the whole house is that way the easiest would be to reverse the L and N at the cu.

[Crossy]

Hmmm, trumped by Wayned for the second time in this thread, want my job mate?

 

One point, the switch pilots are often wired across the switch (if there's no neutral at the switch), the tiny current they use bleeds through the load. This means of course that the pilot is on when the switch is off, and off when the switch is on. The idea being that you can find the switch in the dark :)

 

[wayned]

37 minutes ago, Crossy said:

Hmmm, trumped by Wayned for the second time in this thread, want my job mate?

 

One point, the switch pilots are often wired across the switch (if there's no neutral at the switch), the tiny current they use bleeds through the load. This means of course that the pilot is on when the switch is off, and off when the switch is on. The idea being that you can find the switch in the dark :)

 

Don't want your job, I just was bored!  You just have to get up earlier like me!

[Crossy]

1 hour ago, wayned said:

Don't want your job, I just was bored!  You just have to get up earlier like me!

 

I assumed you hadn't retired to bed yet :)

 

To our OP.

If you have a confirmed reverse polarity, it is imperative that you get it sorted ASAP if not sooner. You could combine it with installing an RCD / RCBO (Safe-T-Cut).

 

 

[DUNROAMIN]

1 hour ago, Crossy said:

 

I assumed you hadn't retired to bed yet :)

 

To our OP.

If you have a confirmed reverse polarity, it is imperative that you get it sorted ASAP if not sooner. You could combine it with installing an RCD / RCBO (Safe-T-Cut).

 

 

Thanks for that, been a great help. One more question, can you turn off the power at the pole meter or does this have to be done by power company. I have seen a couple of so called electricians working on other homes and seen them turn of the mains at the pole?  I have enough knowledge to fix the polarity issue, however, don't won't to play around with live power.

[Crossy]

There is no fuse or isolator at the pole (so those live tails have no over-current protection other than the HV fuse at the transformer), they usually pull out the outgoing tails from the meter (they're rarely sealed).

 

Of course if they pull both tails and don't mark them that's the usual source of revered polarity.

 

If you don't want to do it live (and I really wouldn't recommend you do anyway) get a local sparks to do it for you under close supervision.

[DUNROAMIN]

Thanks to everyone for help with this topic, take care.

[Strange]

10 hours ago, wayned said:

If they are the fluro will glow as you are switching the N.

 

Can you please explain this? 

 

Not denying; I want to understand. 

[Crossy]

38 minutes ago, Strange said:

 

Can you please explain this? 

 

Not denying; I want to understand. 

 

I'm not entirely sure of the mechanism, the glow is pretty dim, probably capacitive coupling to earth, but it definitely happens.

[wayned]

The color we see is produced by a fluorescent coating on the glass of the bulb, which converts some of the invisible ultraviolet light produced by the excited gas atoms into visible light. When you cut off the current, you stop exciting the gas atoms and thus stop producing new ultraviolet light, but since you are switching the neutral rather than the live, the excitation remains in the  material and the capacitive coupling to earth, as Crossy said, most likely to the case of the lamp allows it to glow. Switching the live will correct the problem.

[Strange]

3 hours ago, Crossy said:

probably capacitive coupling to earth

 

1 hour ago, wayned said:

the excitation remains in the material and the capacitive coupling to earth, as Crossy said

 

Time for a google. 

 

What about when OP was saying that his down lights were coming on during lightning strikes? 

 

I mean I completely agree L needs to be switched, but what I don't get is WHY this would happen. 

 

My buddy has a place that trips the RCD when lightning strikes. Everything is wired correctly that I can see. He was afraid of leaving his place for a few days because of refrigerator/freezer thawing. I told him to turn the RCD off when he goes out of town for a few days, but couldn't come up with an actual solution other than that. 

[Crossy]

We have dimmers that are upset by surges, even the airon starting on a bad day will change the brightness level. I suspect something akin to this is causing the downlight issue.

 

RCDs can do interesting things when subjected to surges, if the core saturates the mechanism thinks it's a leak and opens the circuit.

 

If you have a freezer put it on an unprotected supply, no regs like the UK to prevent you doing this, RCD trips freezer stays on. Ours are wired like this.