supplementary bonding

[Rob69]

Hi ,

when doing a test and inspect what is the best way to confirm if supp bonding in place? is it by visually checking accessories and looking for the earth cables?

can it be done by testing as well or will parallel paths disturb the readings?

Is it just basically a visual check ?

thanks

rob

 

[Theorysparky]

you can test..

there will not be any parallel paths as you test between items in the bathroom

lights-pipes

shower- pipes etc

testing point to point

 

[choccy]

the best way to test your bonding is by your r2 wander lead test, this will confirm that the bonding is connected to the MET at the DB

 

[Andy™]

you can test..there will not be any parallel paths as you test between items in the bathroom

lights-pipes

shower- pipes etc

testing point to point

there will be plenty parallel paths theory - if you test between cold pipe & radiator, you may be getting the bonding, but you will also be gettng cold pipe back to heating/boiler, and then through heating pipe. if there is a break (or pushed under the floor) on the earth, it wont show

 

[Andy™]

the best way to test your bonding is by your r2 wander lead test, this will confirm that the bonding is connected to the MET at the DB

this will confirm there is a path back to MET. not that the path is thtough the conductor under test. you would have to disconnect one end to test this

 

[NozSpark]

adn supplementary bonding is not connected "directly" to the MET

 

[Theorysparky]

[quote name='Andy

 

[Andy™]

not always. if there is a solid copper pipe between the 2, then your reading isnt going to be much (if any) difference by sticking a bit of 4mm between them

 

[PC Electrics]

ID those circuits that enter the bathroom.

Disconnect cpc's at board.

Test for continuity between these cpcs and pipework and between each other.

If you have continuity (<0.5ohm) you have supplementary bonding, if not you haven't.

The supplementary bonding connections should be accessible for inspection and test same as any other connection, but they may be outside the bathroom (so, lights to shower to pipes sbc may be in the loft or airing cupboard.

Of course, if the installation meets the conditions for sbc omission as per 17th edition, then you needn't bother looking or testing for sbcs (eg an older install might have a 30mA main switch!)

 

[a1spark]

Supplementary bonding in a Bathroom etc. is installed to reduce the touch voltage to 50V or less between Exposed conductive parts and also to extraneous conductive parts ,it is not directly concerned with any connections back to the MET. The theory is to ensure that the resistance {r} value measured across any of the two conductive, parts mentioned above,multiplyed by the current causing effective operation of the largest Protective device in the location [ x5 for a b-t ype 60898 ] {Io} results in 50v or less.

In a 17th Edition Installation the resistance value is increased to 1666 ohms due to the 30mA as Io in the equation.......the extraneous conductive parts are required to be effectively connected back to the MET and supplementary bonding will still be required if this resistance back to the MET lies in the region of 1667 ohms -22,000 ohms.....anything above 22,000 ohms means it is not classed as being an extraneous conductive part and can be omitted from the requirements of supp. bonding.

 

[JUD]

Supplementary bonding in a Bathroom etc. is installed to reduce the touch voltage to 50V or less between Exposed conductive parts and also to extraneous conductive parts ,it is not directly concerned with any connections back to the MET. The theory is to ensure that the resistance {r} value measured across any of the two conductive, parts mentioned above,multiplyed by the current causing effective operation of the largest Protective device in the location [ x5 for a b-t ype 60898 ] {Io} results in 50v or less.In a 17th Edition Installation the resistance value is increased to 1666 ohms due to the 30mA as Io in the equation.......the extraneous conductive parts are required to be effectively connected back to the MET and supplementary bonding will still be required if this resistance back to the MET lies in the region of 1667 ohms -22,000 ohms.....anything above 22,000 ohms means it is not classed as being an extraneous conductive part and can be omitted from the requirements of supp. bonding.

Good explanation a1spark.

Just a quick follow up question to see if I've got this right.

Let's say you have a 10kW shower on a 45A Type B breaker. Fault current for instantaneous operation would be 225A (45 x 5).

Would this mean that the reading between the shower and any other conductive part in the bathroom should be less than 0.22Ω (50V

 

[a1spark]

Yes Jud ,thats the correct method of determining Supplementary Bonding

requirements ,in a pre-17th edition compliant installation