does heating radiator needs bonding?

[bluesky]

i have seen quite a lot of photos showing radiators having bondings, but most dont have, is it really needed?

cheers

 

[Deleted member 9648]

No.....mostly.
If the radiator is in a special location as defined in the BRB supplementary bonding may be required between conductive and extraneous conductive parts.
This is where the confusion comes in. An extraneous conductive part is defined as a metallic part not forming part of the electrical installation and and liable to introduce a potential,generally earth.
A radiator is not liable to introduce an earth potential and is therefore not an extraneous conductive part.
The pipes supplying the radiator however may be extraneous conductive parts and so may need supplementary bonding within a special location.
An exception may be where a radiator is fixed to structural steel within the fabric of the wall for example, and so may introduce an earth potential to the special location.

 

[WayneL]

No.....mostly.
If the radiator is in a special location as defined in the BRB supplementary bonding may be required between conductive and extraneous conductive parts.
This is where the confusion comes in. An extraneous conductive part is defined as a metallic part not forming part of the electrical installation and and liable to introduce a potential,generally earth.
A radiator is not liable to introduce an earth potential and is therefore not an extraneous conductive part.
The pipes supplying the radiator however may be extraneous conductive parts and so may need supplementary bonding within a special location.
An exception may be where a radiator is fixed to structural steel within the fabric of the wall for example, and so may introduce an earth potential to the special location.

Hi Wirepuller,

Although I agree with the gist of what you are saying, I wanted to point out that if the pipes supplying the radiator were extraneous conductive parts, then they would need bonding to the MET and not supplementary bonding.
This is regardless of whether it's a special location or not.

 

[Deleted member 9648]

Extraneous conductive parts within a special location can be metallic services which may introduce an earth potential to the special location from outside the special location but still within the equipotential zone, and may require supplementary bonding due to the perceived increased shock risk within a special location.
Extraneous conductive parts coming from outside the equipotential zone would require main bonding whether within or not within a special location.
In the example of a radiator fixed to structural steel within the fabric of the building,this steel would likely have been main bonded elswhere if it was part of the building structure in contact with the ground,but the radiator within a special location would be an extraneous conductive part within that location and so may need to be supplementary bonded.

 

[WayneL]

Extraneous conductive parts within a special location can be metallic services which may introduce an earth potential to the special location from outside the special location but still within the equipotential zone, and may require supplementary bonding due to the perceived increased shock risk within a special location.
Extraneous conductive parts coming from outside the equipotential zone would require main bonding whether within or not within a special location.
In the example of a radiator fixed to structural steel within the fabric of the building,this steel would likely have been main bonded elswhere if it was part of the building structure in contact with the ground,but the radiator within a special location would be an extraneous conductive part within that location and so may need to be supplementary bonded.

Regulation numbers, please - I've never heard anything of the likes of that - and I've read GN8!

 

[scotsparky]

GN8? look at GN7 Reg701.415.2,701,411.3.3 ,411.3.1.2 ,411.3.2, 415.2.2 701,415.2

 

[WayneL]

GN8? look at GN7 Reg701.415.2,701,411.3.3 ,411.3.1.2 ,411.3.2, 415.2.2 701,415.2

The regulation numbers you have quoted have nothing to do with this discussion

Yes, we all know the method of 'Additional Protection' provided by supplementary bonding in a bathroom - just as we know the three conditions that render it un-neccessary.

Supplementary Bonding is, as the name implies, supplementary (additional), and is used to re-enforce the equipotential zone in a bathroom.

It has nothing to do with pipework in a bathroom being 'extraneous' as was stated above - if it was extraneous it would have to be main bonded back to the MET (as I stated earlier)

In answer to the OP, No, the radiator wouldn't need bonding unless the pipework supplying it was 'Extraneous', or it was located in a special location and the conditions for ommiting 'supplemetary bonding' weren't met.

 

[Deleted member 9648]

See OSG page30 4.5 and 4.6 where supplementary bonding of extraneous conductive parts in locations coming under section 7 of bs7671 are described.
The services entering a special location may be classed as extraneous even though the location is wholly within the equipotential zone ,and those services are main bonded elsewhere.
See also 715.415.2 where supplementary bonding of extraneous conductive parts within a bath/shower room is described.

You will note that both the references above use the term extraneous.
I interpret the term extraneous as introducing an earth from outside of the equipotential zone....which would require main bonding.Or in the case of a bathroom,introducing an earth potential to a special location from elsewhere within the equipotential zone which may require supplementary bonding due to the increased shock risk,if the 3 conditions to omit are not met.

 

[GT1]

does anyone else find... that a lot of people get their knickers in a twist with bonding..!

I know that the 16th ed had virtualy everything bonded to everything else, and ive seen the evidence of this underneath many a kitchen sink..!!

However, the 3 conditions allowing supp bonding to be ommitted are pretty commonplace in general domestic work.. Off the top of my head these are that the instalation is TNCS/TNS, that the bathroom circuit (or other circuit) is RCD protected, and that the resistance of the extaneous conductive parts back to the met is below a certain level.. (0.05 ohms at a guess).

Any electrical work in the bathroom more than likely means the circuit protection is going to need upgrading to RCD protection anyway, and more often than not the other two conditions will be met too..

Personaly I'd rather swop out an MCB to the protected side of the board, or out completely for an RCBO, than mess about bonding everything to everything else any day of the week.. (if conditions permit)

 

[Deleted member 9648]

Cant remember the last time I faffed around with 4.0mm in a bathroom.....3 conditions are
1. 30ma RCD to all circuits within the bathroom
2. continuity <1667 ohms between extraneous and conductive parts
3. Required disconnection time met for all circuits

Agree.....avoid supplementary if I possibly can.

 

[kevben]

Agreed When we do a new shower and ther's no supp bond , we always try to put existing lights onto RCD just to save the messing about with clamps etc
Nightmare bonding to light etc...