Bonding, plastic and metal pipes

[philrosenberg]

Hi everyone, looking for advice on bonding.
My central heating system uses both plastic and metal pipes, so I've bonded all the metal parts but wasn't sure about the bathroom.

The bathroom radiator has metal pipes leading into some wooden boxing then turns to plastic.
My question is does it need bonding?

Ordinarilly I would have bonded it anyway, but i was hoping that it might count as a plastic pipe installation so I wouldn't need to supplimentary bond it either (the only other thing to supplimentary bond is the shaver socket and it is going to be a pig to connect them). I assume that if it is bonded then it will definitely need supplimentary bonding.

Cheers for any help

Phil

 

[RF Lighting]

You do not need to bond the metal tails if it is connected to plastic.
Do you try searching for this? It's been covered loads on here before.

 

[philrosenberg]

Thankyou for the fast reply RF
I did not search first, my appologies.

I seem to have missunderstood the definition of extraneous. I always thought that the point of bonding was to trip your rcd in the (seemngly very unlikey) case that the pipework became live due to a fault in the house. Reading other posts this is clearly not generally the case. It is really there to ensure the pipework is at the same potential to your earth so that if you touch your washing machine and water pipe you won't get shocked (please someone correct me if I'm wrong)
Does this mean that by connecting all the bits of copper in my house to earth I've actually made it less safe by intoducing more earth points to shock myself through in the case of me becoming live during a fault?

 

[RF Lighting]

Bonding is only nessacery in a room containing a bath or shower as in these rooms you are considered to be a a greater risk of electrocution (wet skin, bare feet etc) so this is why these locations need to be equipotentially bonded. You are right about the reasons for equipotential bonding being carried out.
By "bonding all the bits of copper" do you mean all the metal tails in the bathroom or all the pipes in the house?
I hope I have misunderstood your post and that you don't actually have a washing machine in the bathroom, but if you do how is it connected to the mains? Is it RCD protected? Is it on show or in a cupboard? How close is it to the sink or bath?

 

[philrosenberg]

No I don't have a washing machine in my bathroom. I was referring to main bonding, rather than supplimentary bonding when talking about the washing machine.
Okay so as far as I can gather, anything where there is a run of plastic between the copper pipe and the stopcock (which is steel back to the outside) is not extraneous and doesn't need main bonding. Similarly these parts will not need supplimentary bonding because they are isolated from earth.

Given that I've already added main bonding to some of the copper tails, should I remove it or just leave it?

Feel like a bit of an idiot really, especially as I've waisted a tenner on a second roll of Earth cable

 

[Jaymack]

This will help: -

http://www.iee.org/Publish/WireRegs...tumn_plastic_pipes_to_bond_or_not_to_bond.pdf

Jaymack

Sometimes I sits and thinks; and other times I just sits.

 

[viewer]

Despite lots of threads and the reference to the doc referenced by Jaymack, there really is some conflict with advice. On an earlier thread I was, quite rightly, slapped on the wrist by bas for using the "don't bond if plastic pipes" in too simplistic a manner. He pointed out the need to take into account the conductivity of the water plus additives in a central heating system. Rightly, or wrongly, using the resistance figures in Paul Cook's article, I get a conclusion that to get down to a (potential) current of 1mA through a radiator would require 5 metres of plastic 10mm pipe (and pro-rata). Many systems are not all plastic but have copper then the feeds into the bathroom use plastic. These will have very short distances between the copper and the radiator. For many the ch pump will be close to the bathroom. Anybody done any actual measurements or know of other sources of advice?