Earthing Pipes?
- Thread starter dave12
- Start date
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We do it so that you can't get a fault condition that makes your radiators or bath taps or whatever live, as this would be a Bad Thing (TM) 
The idea is that every single metal object that has some sort of a path to earth anyway (e.g. via the water main or gas main) is given a high-quality, low impedance connection back to the supply earth via a thick copper cable.
There are two aspects to the protection - first, a low resistance path to earth will make protective devices more certain to work if a live to metalwork fault occurs. Secondly, if you have a fault somewhere, current flowing in the earth wiring will cause the voltage on that wiring to rise relative to true earth potential. This could cause a shock to someone touching, for instance, the case of a faulty washing machine and a water tap at the same time. In order to minimise this risk, an 'equi-potential zone' is created by connecting the services to the main earthing point. Such services are:
Water Pipes
Gas Pipes
Oil Pipes
Central Heating
Metallic Ventilation Trunking
Exposed Parts of Building Structure
Lightning Conductor
Any other Metallic Service
You have to pay particular attention in areas like bathrooms to ensure that all the metalwork there is bonded together locally to create a "local equi-potential zone", this should include:
Hot & Cold water pipes to sink, bath, shower
Waste pipes (metal)
Central heating pipes, radiator, towel rail
Electric towel rail, radiant or convector heater
The bath (if metal - don't rely on the pipes alone).
A couple of points:
1) Anything connected by plastic pipes should not be bonded
2) You may not use the incoming water or gas pipes as the earth
The idea is that every single metal object that has some sort of a path to earth anyway (e.g. via the water main or gas main) is given a high-quality, low impedance connection back to the supply earth via a thick copper cable.
There are two aspects to the protection - first, a low resistance path to earth will make protective devices more certain to work if a live to metalwork fault occurs. Secondly, if you have a fault somewhere, current flowing in the earth wiring will cause the voltage on that wiring to rise relative to true earth potential. This could cause a shock to someone touching, for instance, the case of a faulty washing machine and a water tap at the same time. In order to minimise this risk, an 'equi-potential zone' is created by connecting the services to the main earthing point. Such services are:
Water Pipes
Gas Pipes
Oil Pipes
Central Heating
Metallic Ventilation Trunking
Exposed Parts of Building Structure
Lightning Conductor
Any other Metallic Service
You have to pay particular attention in areas like bathrooms to ensure that all the metalwork there is bonded together locally to create a "local equi-potential zone", this should include:
Hot & Cold water pipes to sink, bath, shower
Waste pipes (metal)
Central heating pipes, radiator, towel rail
Electric towel rail, radiant or convector heater
The bath (if metal - don't rely on the pipes alone).
A couple of points:
1) Anything connected by plastic pipes should not be bonded
2) You may not use the incoming water or gas pipes as the earth
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ban-all-sheds - "A couple of points:
1) Anything connected by plastic pipes should not be bonded"
Why not?
Plastic poses as greater risk as copper if not more.
I was under the impression that you have to buy some sort of special connector for the plastic that can be earthed, or use a bit of copper when connecting to taps, so that could be earthed
1) Anything connected by plastic pipes should not be bonded"
Why not?
Plastic poses as greater risk as copper if not more.
I was under the impression that you have to buy some sort of special connector for the plastic that can be earthed, or use a bit of copper when connecting to taps, so that could be earthed
B
breezer
sterose said:
you do not bond plastic pipes for one reason. They do not conduct electricity
masona said:
I don't remember saying that....
sterose said:
The point is that if you've got plastic pipes, then there's no way for the item (e.g. CH rad) to become live - there is no electrical path to it. But if you earth it, then 2 problems arise.
1) It now offers a path to earth, and therefore a path for a shock current to flow through you. If you had a live wire in one hand and touched the rad with the other, it'd be far better if there was no path for the current to flow. If you aren't earthed then touching a surface that is at 240v above earth won't harm you.
2) You've opened up the possibility that if something went wrong with the earthing system, the rad could become live.
What I'm thring to get through here is that water does conduct electricity and therefore needs to be earthed.
The fact that water does not conduct water *very well* is the whole reason for earthing.
e.g. if you have a 40amp breaker in your shower and the water conducts a maximum of 39 amps, your'e going to be set on fire before the fuse blows.
Earthing reduces the resistance so all you will get with earthed pipes is a quick shock (of >40 amps) before the fuse blows.
Understand?
The fact that water does not conduct water *very well* is the whole reason for earthing.
e.g. if you have a 40amp breaker in your shower and the water conducts a maximum of 39 amps, your'e going to be set on fire before the fuse blows.
Earthing reduces the resistance so all you will get with earthed pipes is a quick shock (of >40 amps) before the fuse blows.
Understand?
Re earthing rads on plastic pipes - am I wrong? I always thought that you didn't, any more than you earthed towel rails (ordinary, not heated), or steel shelves etc.
Does an unearthed rad provide a good enough path to earth via the water in the plastic pipes for there to be a shock hazard?
And as an aside, why can't you get plastic radiators these days?
Does an unearthed rad provide a good enough path to earth via the water in the plastic pipes for there to be a shock hazard?
And as an aside, why can't you get plastic radiators these days?
You dont earth steel shelves and towel rails because there is NO path to earth (assuming is is fixed to brick or wood) unless it is connected to something with a path to earth.
You do earth radiators though because they are generally somewhere conencted to earth, usually at a boiler (because the metal of the boiler must be earthed).
Water does conduct electricity but has a high resistance.
This means that, without me knowing the exact resistance, a current that is less than the fuse rating can flow through you.
Like i said, if the resistance of water means that a current of 39 amps flows from your shower into you, but the shower fuse rating is 40amps, the fuse will never blow because it is still below its rating.
However, 39amps can damage you if not set you on fire.
Please ask further if you dont understand.
As a final point, a totally earth free environment is the safest place to be, eg. you could touch the 240volts mains and not be electrocuted. BUT no place in a house is totally earth free, eg. there is always something that will conduct electricity. The problem in bathrooms is that there is plenty of water and metal, and electricity if you have a shower. If an electric appliance fails somehow, it is the most likely place for you to come into contact with the faulty appliance AND be touching something with a path to earth.
Also, save yourselves time by simply learning about this instead of arguing with me. I know im right. Because when I argue, i always know im right.
You do earth radiators though because they are generally somewhere conencted to earth, usually at a boiler (because the metal of the boiler must be earthed).
Water does conduct electricity but has a high resistance.
This means that, without me knowing the exact resistance, a current that is less than the fuse rating can flow through you.
Like i said, if the resistance of water means that a current of 39 amps flows from your shower into you, but the shower fuse rating is 40amps, the fuse will never blow because it is still below its rating.
However, 39amps can damage you if not set you on fire.
Please ask further if you dont understand.
As a final point, a totally earth free environment is the safest place to be, eg. you could touch the 240volts mains and not be electrocuted. BUT no place in a house is totally earth free, eg. there is always something that will conduct electricity. The problem in bathrooms is that there is plenty of water and metal, and electricity if you have a shower. If an electric appliance fails somehow, it is the most likely place for you to come into contact with the faulty appliance AND be touching something with a path to earth.
Also, save yourselves time by simply learning about this instead of arguing with me. I know im right. Because when I argue, i always know im right.
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