Supplementry Bonding with previous edition regs

[Amp David]

Am I right in saying that back in the earlier edition of the regs, Supp Bonding was only required in bathrooms if the electrical accessory was in zone 1 2 or 3?

 

[ackbarthestar]

Am I right in saying that back in the earlier edition of the regs, Supp Bonding was only required in bathrooms if the electrical accessory was in zone 1 2 or 3?

In the 15th ed it was also a requirement in kitchens - I still think it should be, but then that could be regarded as contentious...

Its based on the fact that there were few MCBs (BS 3871)and more or less no RCDs (BS EN 61008) except for VOELBs and the occasional RCCB (BS4293) in TT systems. Fixed equipment had a maximum disconnection time of 5 seconds So you could be in a bath with an electric immersion heater right above you, a fault then developed which might last up to 5 seconds. Your only protection was/is in some cases, supplementary equipotential bonding, clamping the voltage rise to below 50V (touch voltage)

 

[Amp David]

How would it be best described on a EICR then to say that it is present, can't be seen due to being boxed in but resistance between exposed conductive parts and extraneous conductive parts is low 0.03ohms.

 

[ackbarthestar]

How would it be best described on a EICR then to say that it is present, can't be seen due to being boxed in but resistance between exposed conductive parts and extraneous conductive parts is low 0.03ohms.

As long as it does what it was supposed to do then it cannot be said that it is unsafe. since it would be compliant with the 15th ed. However, it will not comply with he current regs, so it is likely to draw the C3 code and noted on the EICR.

 

[Guitarist]

My bad

 

[Engineer54]

We still supplementary bond our commercial type kitchens, communal dressing/shower rooms and even the domestic kitchens and bathrooms. But then ''All'' our kitchens are s/steel basins and or worktops and chromed copper waste pipes throughout!!

 

[Knobhead]

With the introduction of more and more plastic piping it’s about time it was brought back in to regular use.
Call me old fashioned if you like but it had it’s advantages. I’m sorry but I prefer “if it don’t move, bond it”.

Just hope the ex doesn't read this!

 

[Geoffsd]

More and more plastic piping should result in less bonding.

Bonding is not fitted so that the OPD will operate.

 

[morph]

with 16th it was a req
with 17th it can be used as a means of providing additional protection
commercial kitchens still should have it

 

[Amp David]

When checking then, its aim is to keep possible touch voltage to <=50 volts.

 

[ackbarthestar]

When checking then, its aim is to keep possible touch voltage to <=50 volts.

It works primarily for the old BS 3036 fuses where the 's/c' disconnection times for a current less than the minimum short circuit current to disconnect in < 0.4 secs since these are not as fast as MCBs. (0.1 or possibly as low as 0.01s) and will allow a certain amount of fault current through.

Zs <= 50 / Ia or more commonly appropriate to modern systems with RCDs as 50 / IAN.

You could, of course, use Ia in which case you would take the worst case which would be a fault on the largest item of equipment

 

[Amp David]

If bonding has been carried out between extraneous parts, but not to the CPCs, but resistance between all extraneous parts and the CPC terminals of light, shower or what ever's installed give a resistance low enough to prevent voltage rising above 50v, is this acceptable?

 

[ackbarthestar]

Ah, now you are introducing a bonding zone that is not connected to the MET, which, if I recall makes it 'earth free'.
Now from 418, it becomes clear that this type of protection should only be installed under the supervision of trained personnel, that doesn't include domestic customers.

If there are metallic parts that are separated from an earth potential such as radiators supplied by plastic pipework, then I wouldn't connect them together.

 

[Amp David]

Just trying to forget the existence of plastic piping for now and basing everything on copper pipework. Not many properties that i've come across that would have or need supp bonding sorting which have plastic plumbing.

 

[Guitarist]

If bonding has been carried out between extraneous parts, but not to the CPCs, but resistance between all extraneous parts and the CPC terminals of light, shower or what ever's installed give a resistance low enough to prevent voltage rising above 50v, is this acceptable?

Do you mean with a connection to the MET, but not to any CPC's or just between ECP's themselves?

 

[ackbarthestar]

If bonding has been carried out between extraneous parts, but not to the CPCs, but resistance between all extraneous parts and the CPC terminals of light, shower or what ever's installed give a resistance low enough to prevent voltage rising above 50v, is this acceptable?

Ok,
If you connect all the metal fittings together, assuming you have all copper pipework then it is likely to be main equipotentially bonded at source, in which case you you are creating a local bonding zone in that location. If you now cross bond the cpcs of the circuits entering that zone to the extraneous conductive parts you will achieve a shared R2 between all of the circuits this lowering the Zs of each circuit while providing your local equipotential bonding zone.

That's fine if you are using BS3036 fuses without RCD protection and was the acceptable method of providing protection previously

 

[Amp David]

Do you mean with a connection to the MET, but not to any CPC's or just between ECP's themselves?

Between exposed conductive parts and extraneous and just exposed conductive parts.

 

[Amp David]

Ok,
If you connect all the metal fittings together, assuming you have all copper pipework then it is likely to be main equipotentially bonded at source, in which case you you are creating a local bonding zone in that location. If you now cross bond the cpcs of the circuits entering that zone to the extraneous conductive parts you will achieve a shared R2 between all of the circuits this lowering the Zs of each circuit while providing your local equipotential bonding zone.

That's fine if you are using BS3036 fuses without RCD protection and was the acceptable method of providing protection previously

Even if you have 60898 or 3871 breakers say for lighting, then if you were to test for a minor works say for a replacement shower that had rcd/rcbo, supp bonding still has to provided, for the non rcd circuit/s.

So if all extraneous parts are tiled in behind a bath or boxed in for what ever reason, and there is no possible way to connect supp bonds from extraneous to conductive. But, for example, when you test between the hot, cold and heating you get low readings and between these and light fitting cpc you also have a low reading, if this resistance figure provide the 50 volt or less does it comply?

 

[ackbarthestar]

Even if you have 60898 or 3871 breakers say for lighting, then if you were to test for a minor works say for a replacement shower that had rcd/rcbo, supp bonding still has to provided, for the non rcd circuit/s.

So if all extraneous parts are tiled in behind a bath or boxed in for what ever reason, and there is no possible way to connect supp bonds from extraneous to conductive. But, for example, when you test between the hot, cold and heating you get low readings and between these and light fitting cpc you also have a low reading, if this resistance figure provide the 50 volt or less does it comply?

You can only do so much with what you've got. If access to the extraneous parts is hidden behind tiles you will not be able to supp. bond directly. In most cases cross bonding locally to the hot and cold pipework, radiators etc would be sufficient.

If you are replacing the shower unit you might be able to slip a 4mm2 up and across to the lighting circuit and to other metallic parts. I think that 701.415.2 gives more information regarding this