# Domesticsuplementary bonding again

Discuss suplementary bonding again in the Electrical Forum area at ElectriciansForums.net

T

#### thekingiam

Welcome to ElectriciansForums.net - The American Electrical Advice Forum

just trying to get my head around this as never tested before, bathroom pipes all circuits rcd protected no power except lights, connected one probe to landing cpc in socket and the other to sink pipe tested insulation resistance on 500 volts 1 meg ohm meter reading 0000.00 X underneath 1 volt checked continuity at 20 ohm and got 1.3 ohm.
am i doing this correctly and if so as it's not above 0.2 M ohm do i take it that i need suplementary bonding?

This official sponsor may provide discounts for members

#### trev

##### -
0.023Meg mate. The threshold is 23k ohms.

T

#### thekingiam

so am i doing test right?
and do i need sup bonding?

#### trev

##### -
Test between the part you are doubtful about and the MET. If the result is >23k ohms it doesn't need bonding

T

#### thekingiam

same result from met, sup bonding?

#### trev

##### -
All main bonding in place and everything RCD protected? I've been talking about main bonding mate sorry.

T

#### thekingiam

all main bonding in place and rcd protected lol

#### trev

##### -
If all that's in place supplementary bonding is not required.

T

#### thekingiam

thankyou, so in this circumstance no need to test ? sorry i got lost!

#### ackbarthestar

##### -
Mentor
Arms
Measure between simultaneously accessible metal parts, such as radiators, taps, pipework and cpcs of circuits within the bathroom.

the values you are looking for are <0.05 ohms or >22k ohms

The formula for the latter is Rx > Uo/IAN -Rb, where Uo = 230V, IAN = 10mA, Rb = 1k ohm

T

#### thekingiam

would i need to do this as only crcuit is lighting ,protected by rcd and out of reach?

#### ackbarthestar

##### -
Mentor
Arms
Start with 701.415.2 then if there is still doubt then look at 415.2.2.
From your results in the OP, there is not enough IR to be isolated and too much resistance to be effective enough to keep the touch voltages to a minimum
If there is RCD protection, MPB and the bathroom lighting circuit complies with 41.1 then SBCs may still be required.
The chances of a fault caused from the lighting circuit is probably slight but there are other circuits in the property that may transfer a fault voltage onto the pipework in the bathroom location.
Not that it has ever happened on my watch.....

T

#### thekingiam

ok retested low ohm meter got 0.47 ohm so
0.47 x 50 / 0.03 = 783.33 well below 16670
so no sup bonding required, am i correct anyone?

#### rich.250

##### -
Arms
With supplementary bonding you are checking to see that the touch voltage between simultaneously touchable parts will not exceed 50v under fault conditions.
If all ccts are 30mA protected you are looking at 50/0.03 is 1667 ohms. Between all pipe work and the MET.
Above this but below 23k ohms will require supplementary bonding.

This formula proves 'effectively connected to the MET'
Obviously if you have a non Rcd cct you need to replace the 0.03 with the fault current required to operate the OCPD.

Hope this makes sense!!

T

#### thekingiam

where does the 23k ohms come from? is it just a number given or is there a formula that has a relevants?

This official sponsor may provide discounts for members

Reply to suplementary bonding again in the Electrical Forum area at ElectriciansForums.net

This official sponsor may provide discounts for members