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Supplimentary bonding where to put earth clamps?
- Thread starter BigHammo
- Start date
All screwed terminations must be accessible for testing, inspection and fault finding. This means they must either be visible and obvious or their location identified and accessible. Under the floor is not considered accessible unless there is an access trap, suitably marked.
Is there an airing cupboard? Or access to the pipework in the loft?
Roll on all-plastic plumbing.
Is there an airing cupboard? Or access to the pipework in the loft?
Roll on all-plastic plumbing.
The sink, bath, toilet should not be a problem as I can hide the cables and straps. All others are installed to the shaver and fan switches. The problem is the towel radiator. I suppose I could get a small earth clamp but the cable and strap notice could be seen.
How long would you suggest they should be?
How long would you like?
More seriously, assuming that there is no acceptable way of bonding the pipes, the towel radiator can be electrically isolated from the system. Normally these radiators have entry pipes from below with straight valves so they would need to be long enough to avoid possibility of touching the copper. If they "appear" through a tiled wall or floor it is possible to get snap on covers which protect the copper/plastic joint.
More seriously, assuming that there is no acceptable way of bonding the pipes, the towel radiator can be electrically isolated from the system. Normally these radiators have entry pipes from below with straight valves so they would need to be long enough to avoid possibility of touching the copper. If they "appear" through a tiled wall or floor it is possible to get snap on covers which protect the copper/plastic joint.
I was afraid that was what you were thinking.
Water conducts electricity.
CH water with sludge and additives conducts it even more.
So a short length of plastic pipe does not provide electrical isolation - the radiator remains an extraneous-conductive-part...
Water conducts electricity.
CH water with sludge and additives conducts it even more.
So a short length of plastic pipe does not provide electrical isolation - the radiator remains an extraneous-conductive-part...
Article on this very matter by Paul Cook of the IEE : http://www.iee.org/Publish/WireRegs/EarthingPlasticPipes.pdf
Time to be shot down.
Paul Cook's article seems to be used often and misused / abbreviated to suggest any plastic pipe will give the required separation / resistance. This was my origin. Going to the original article, and working on his figures (20,200 ohms per metre for central heating water in 15mm pipe); With no allowance for paint and other resistances, I get-
The water in a plastic 10mm central heating pipe would have a resistance of about 45,450 ohms per metre.
Given a voltage of 230 volts then to get down to (the imperceptible) 0.5mA requires a resistance of 460,000 ohms. Roughly equal to 10 metres of plastic pipe.
If this is correct then a bonding connector should join any metal at either end of 10mm plastic central heating pipe if it is less than about 10m long. This would apply to both pipes into a radiator as voltage could applied to one or both.
In this case the advice that plastic pipwork in a bathroom should not be bonded ignores the small size of most bathrooms and the nearest metal pipework / cylinder / manifold could be close. As an example a large copper central heating pipe may run through the room behind boxing with plastic small bore running off to each radiator (my own is like this).
Have I missed something here?
Whatever - thanks for the wake-up call.
Paul Cook's article seems to be used often and misused / abbreviated to suggest any plastic pipe will give the required separation / resistance. This was my origin. Going to the original article, and working on his figures (20,200 ohms per metre for central heating water in 15mm pipe); With no allowance for paint and other resistances, I get-
The water in a plastic 10mm central heating pipe would have a resistance of about 45,450 ohms per metre.
Given a voltage of 230 volts then to get down to (the imperceptible) 0.5mA requires a resistance of 460,000 ohms. Roughly equal to 10 metres of plastic pipe.
If this is correct then a bonding connector should join any metal at either end of 10mm plastic central heating pipe if it is less than about 10m long. This would apply to both pipes into a radiator as voltage could applied to one or both.
In this case the advice that plastic pipwork in a bathroom should not be bonded ignores the small size of most bathrooms and the nearest metal pipework / cylinder / manifold could be close. As an example a large copper central heating pipe may run through the room behind boxing with plastic small bore running off to each radiator (my own is like this).
Have I missed something here?
Whatever - thanks for the wake-up call.
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