Ground Earthing and an RCBO

[lom]

On 9/23/2023 at 12:00 PM, Muhendis said:

Depending on the setting of the sensitivity of this device the RCBO will trip if a current of 30milliamps to 10 milliamps is flowing more in one wire than the other.

This minute current can flow through a body and cause the RCBO to trip thus disconnecting power before harm is done. Earth is not needed for this. The person who contacts the faulty equipment is quite likely grounded enough.

Right, but if earth was connected to that equipment then the RCBO would have tripped without a person touching it.

That's basically all you gain by having an earthed system when you are already protected by an RCBO, the earth cable can in this case be small since it only has to handle 30mA.

[sometimewoodworker]

5 hours ago, lom said:

Right, but if earth was connected to that equipment then the RCBO would have tripped without a person touching it.

That's basically all you gain by having an earthed system when you are already protected by an RCBO, the earth cable can in this case be small since it only has to handle 30mA.

There are far more fault conditions than the one you envision. This is why an earth cable is designed to carry hundreds of amps (very short time) not just a few milliampere’s 

[Crossy]

5 hours ago, lom said:

That's basically all you gain by having an earthed system when you are already protected by an RCBO, the earth cable can in this case be small since it only has to handle 30mA.

 

BUT Your RCD/RCBO is an electro-mechanical device, they can and do fail (when did you last test yours?).

 

Also, the 30mA trip current was chosen as a reasonable balance between having nuisance trips and not killing healthy adults. The elderly, infirm or very young could still die.

 

Earthing of Class-1 appliances is the number one safety precaution.

 

It's also worth noting that many modern appliances (like your desktop PC) also require the earth in order for the power-supply interference suppression components to work correctly (it's these components that cause the "tingle" you sometimes get from an un-earthed PC).

[lom]

2 hours ago, Crossy said:

BUT Your RCD/RCBO is an electro-mechanical device, they can and do fail

Make up your mind, you said in a previous post that  RCDs or RCBOs works just fine with multiple earth or no earth at all.. ????

It is fine to have  double protection but then make sure that the earth wire is not just a flimsy convenience earth wire for tripping an RCBO, it should be a real Protective Earth (PE) wire for which there are requirements not relying on an RCBO being present.

 

[sometimewoodworker]

3 hours ago, lom said:

Make up your mind, you said in a previous post that  RCDs or RCBOs works just fine with multiple earth or no earth at all.. ????

Are you trying to be argumentative or do you not understand anything about electrical wiring and safety.

Safety devices fail, not often and not usually but they do fail, so with systems that protect against very severe injuries and death anyone with half a brain cell has multiple layers of protection. 
In the next village last week a very healthy octogenarian lady died by electrocution due to a very unfortunate series of events.

Electricity is dangerous and deadly given just the wrong series of events.

 

But please do try to achieve an individual Darwin Award 

[Muhendis]

11 hours ago, sometimewoodworker said:

Safety devices fail, not often and not usually but they do fail

They certainly do.

Safety-Cut, considered by many to be the Rolls Royce of protective devices and fitted to my CU by the original builder electrician, tripped but failed to cut the power. This I discovered some time after when testing. I replaced it with a less expensive RCBO and all was well again. On stripping the Safety-Cut down I found the trip coil jammed solid due to evidential overheating.

Why did the Safety-Cut trip? Dunno but probably a transient fault. All's well now and tests continue on a monthly basis.

[lopburi3]

7 minutes ago, Muhendis said:

All's well now and tests continue on a monthly basis.

Advise same tests on point of use showers as have had an RCBO unit fail (was years ago and maker has changed system) due to corrosion of the trip reset bar (could not trip - breaker was supposed to trip from bar being released).  

[sometimewoodworker]

2 hours ago, Muhendis said:

Safety-Cut, considered by many to be the Rolls Royce of protective devices

That AFIK is largely due to marketing. In general the more expensive the devices the better quality, but then you have the advertising to add in, I would consider a Schneider product to be better than a Safety-Cut One.

[lopburi3]

1 minute ago, sometimewoodworker said:

That AFIK is largely due to marketing. In general the more expensive the devices the better quality, but then you have the advertising to add in, I would consider a Schneider product to be better than a Safety-Cut One.

Safe-t-cut is best known as made in Thailand and has been available/promoted and used since the mid 70's.  No others were available at that time AFAIK.

[crazykopite]

When I built my place that was the number one item on my list to ensure that my electrics were of the highest standard expensive to do yes but in the long run if it’s stops me or others being electrocuted it’s well worth the investment RIP to the deceased lady 

[xtrnuno41]

On 9/25/2023 at 5:00 AM, transam said:

My A/C, less than 1000w, shower, 4500w, can a 32 amp consumer unit deal with this...?

Strange how back home, everything went through the consumer unit...

Yes it can. However what is the wiring behind the fuse?

A fuse is to protect the wiring on an overload. (too much A cq W)

If you have them both running full, you will have 4500+1000= 5500 W

Maybe you remember P=U X I. So I (amps) = 5500 (W) / 230 (power, V) = 24 A.

 

So MAIN power line should be 4 sqmm. If it is less (2,5 sqmm), your powerline could heat up and be a glow in the dark, up to having fire or a final meltdown of wiring. 

Your wiring to heater should be 4 and, maybe a tappoint to airco in it(?), can be 2.5 again. However only in this case if power line first goes to heater and joint is made in the heater.

 

If it first goes to airco, then ALL wiring should be 4 sqmm.

 

If MAIN powerline is split somewhere in a box, then MAIN is 4 sqmm, also the wiring to heater and airco can have 2.5 sqmm then

 

If there are 2 wires mounted under the same fuse, then to heater 4 sqmm and 2.5 sqmm to airco

 

It depends on where is the joint of the 2 devices.

[transam]

15 minutes ago, xtrnuno41 said:

Yes it can. However what is the wiring behind the fuse?

A fuse is to protect the wiring on an overload. (too much A cq W)

If you have them both running full, you will have 4500+1000= 5500 W

Maybe you remember P=U X I. So I (amps) = 5500 (W) / 230 (power, V) = 24 A.

 

So MAIN power line should be 4 sqmm. If it is less (2,5 sqmm), your powerline could heat up and be a glow in the dark, up to having fire or a final meltdown of wiring. 

Your wiring to heater should be 4 and, maybe a tappoint to airco in it(?), can be 2.5 again. However only in this case if power line first goes to heater and joint is made in the heater.

 

If it first goes to airco, then ALL wiring should be 4 sqmm.

 

If MAIN powerline is split somewhere in a box, then MAIN is 4 sqmm, also the wiring to heater and airco can have 2.5 sqmm then

 

If there are 2 wires mounted under the same fuse, then to heater 4 sqmm and 2.5 sqmm to airco

 

It depends on where is the joint of the 2 devices.

My house is wired with everything 4 sqmm, even the lighting ????, except one run in the kitchen at 2.5...........????

[xtrnuno41]

Grounding, it should be done proper.

Sticking just a rod in the ground isnt the solution and is fake protection. Resistance of grounding should be way down low, to almost zero. Otherwise it is crap.

It must be measured.

Time of placing a rod is also important, in summer the ground is dry and effects resistance negative. In rainy season it is more easy, but problems (resistance) will rise when summer kicks in. The rod has to be in very moist spot

Also material is important, copper is a better conductor and more resistant to corrosion in soil.

I see in Thailand for instance copper plated rods, wouldnt feel happy with them. You already damage the coating by pushing the rod down in the soil.

However they say they are also durable and corrosion resistant, ok.

There are many kinds of steel. But then I dont know why you would copper plate them.

 

Current will go where ever the lowest resistance is.

If the ground system has a high value in resistance, then you are the first one to notice it. Your body is 75% salted water and therefor a good conductor with very low resistance.

 

Your heart is a muscle and can be stopped with electricity. Also your heart can be set to work again with electricity. 

30 mA is "considered safe" , you still could die, depending on YOUR personal health and heart condition. But RCBO's are running on it to protect you. Wise to have them.

Electricity, you cant see, smell, but you will feel it and it and can kill you in jiffy time. 

 

DOnt panic if you notice someone is electrocuted, DONT touch, as you will be taken in the killing line. First find an isolating material to put on victim and then jerk very hard.

Of course it helps if there is a switch close by.

Someone being electrocuted and maybe holding something which is wrong, causes their muscles cramped and they cant let go. You need to act very fast but again no panic.

You have to know what you are doing then, otherwise there will be 2 or more dead.

YOU CANT TOUCH THEM.

 

Sad again, someone died on electricity. 

[OneMoreFarang]

I guess many also read the other recent thread about RCBOs in this forum.

I just posted info about a supplier for Type A and Type B RCCBs and RCBOs. 

 

 

[sometimewoodworker]

1 hour ago, xtrnuno41 said:

Resistance of grounding should be way down low, to almost zero. Otherwise it is crap.

In the U.K. it’s up to 5 ohms in the USA up to 25

[PETERTHEEATER]

On 9/23/2023 at 3:22 AM, cooked said:

It took me two years to find out that someone had swapped the wire colours halfway along the cable run. 

I think the guy who wired my house foresaw the rise in LGBT and wired so as not to cause offence.

[The Theory]

On 9/23/2023 at 9:52 AM, OneMoreFarang said:

If people are not willing to spend a few hundred THB to protect their life, then there is something seriously wrong with those people.

People need to be educated by public TVs, instead of lots of useless programs. Some people even don't know what RCBO is or what it does. ???? 

[The Theory]

2 hours ago, xtrnuno41 said:

Grounding, it should be done proper.

Sticking just a rod in the ground isnt the solution and is fake protection. Resistance of grounding should be way down low, to almost zero. Otherwise it is crap.

Unfortunately "ground check box" not provided in every house by builder and people have no idea that need to have it. 

A ground rod must be buried in a salt and grounded charcoal and be checked every once in a while during dry season. Water and salt may need to be added. 

[sometimewoodworker]

46 minutes ago, The Theory said:

A ground rod must be buried in a salt and grounded charcoal and be checked every once in a while during dry season. Water and salt may need to be added. 

You have forgotten the ritualistic waving of a dead chicken over the rod ????????