Supplementary bonding seems a popular subject. Scenario: A radiator is fixed in a bathroom. The pipe under the floor is copper. The plumber fits a plastic push fit elbow under the floor for each copper tail. Do you bond the radiator or not?
Your opinions
- Thread starter pompeygit
- Start date
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Yes, and also hit the plumber over the head with a big lump of wood.
(there is not enough plastic there to provide isolation so the radiator can introduce a potential - it is also now not effectively connected to the MET - somewhere in limbo!)
(there is not enough plastic there to provide isolation so the radiator can introduce a potential - it is also now not effectively connected to the MET - somewhere in limbo!)
No 
Only ones which can introduce a potential need to be equipotentially bonded. Wether this is by supplementary bonding or accomplished by the main protective bonding is another matter.
Earthing and equipotential bonding are two separate things.
Only ones which can introduce a potential need to be equipotentially bonded. Wether this is by supplementary bonding or accomplished by the main protective bonding is another matter.
Earthing and equipotential bonding are two separate things.
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Take this to the next scenario..........A radiator in a bathroom........under the floor 3m of plastic pipe feed the flow and return of the rad, but the tails to the rad are in copper.........would you bond this rad?
If you measure the resistance between the part (at op temp) and the MET and it exceeds 24k ohms then <10mA can flow in the event of someone touching it and something in fault at mains potential so bonding in this case would not be required.
Wiring matters gives a resistance of "15 mm diameter, water with double dose of inhibitor at 60°C" as 20.2k, multiply by 3 and divide by 2 (flow and return parallel paths) to give a rough idea.
Of course, resistances can change depending on the conditions of the water where you live.
Wiring matters gives a resistance of "15 mm diameter, water with double dose of inhibitor at 60°C" as 20.2k, multiply by 3 and divide by 2 (flow and return parallel paths) to give a rough idea.
Of course, resistances can change depending on the conditions of the water where you live.
Interesting one,
As paul says, one elbow isn't nearly enough to isolate, so you can't chuck your 4mm² back in the van and not bother with it to the rad, but you wouldn't if it was all copper either, I'm not sure the elbow makes a great deal of difference... bear with me on this
Presumably, you would have already bonded the rad pipes elsewhere, say where they pass through a nearby airing cupboard, now the only thing thats going to introduce a potential to the rad is the CH system (through the non-isolating elbow), granted its through a high resistance, but for the potential to be draged away from that of the sup bonding, you are going to need a current flow through it, which of course would require contact between the rad and something at another potential, which of course isn't going to exist....
Don't take it as gospel, but thats my reasoning anyway
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