are main bonds required ???

[WILLRUK]

Evening all,

Just started the first fix in a purpose built block of 4 flats. Gas and water supplies to each unit are run in HDPE and the water/heating installation in each flat are almost entirely in plastic too - save for short copper tails to the rads ( 20cm ish) and taps and the hot/cold at the boiler (80cm ish). My question is are main bonds required ? I can't see how they'd be effective even if I was able to install them anyway.

What's the best way to cover this on the EIC as I don't want to put down as a departure from the regs ?

Any suggestion gratefully received.

Thanks

 

[Lou7]

I would say no bonding required, in the tick box put N/A

 

[Graeme Harrold]

I can see the argument for not bonding the gas, but would personally insist that a plumber installed a short section of copper to provide main bonding point. After all water will conduct, the palstic pipe just makes it an insulated conductor.

 

[Spudnik]

Whatever happens i always run the cables in regardless, plus the gas should be bonded anyway.

 

[zupos40]

I can see the argument for not bonding the gas, but would personally insist that a plumber installed a short section of copper to provide main bonding point. After all water will conduct, the palstic pipe just makes it an insulated conductor.

Click on either of the web address, this article may help, plastic pipe installation do not require bonding, even if short lengt of copper are used at the terminations.

Hep2O® - Electrical Earth Bonding of Plastic Plumbing Systems

www.------.org/publishing/.../pre14-earthing-plastic-pipes.cfm?...

 

[markythesparky]

i maybe wrong but i thought there was an resistance limit between pipes that should be checked to assess if the pipes needed bonding or not.

 

[zupos40]

i maybe wrong but i thought there was an resistance limit between pipes that should be checked to assess if the pipes needed bonding or not.

YES FOR METAL INSTALLATION Gn.3 states 0.005 ohms, not for plastic, as P cook state resistance is likely to be thousands of ohms.

 

[scotsparky]

Zupos just read the post

If the incomming supply of both Gas and Water to the istallation are plastic then no need to bond as thay are insulated. I would not put a bond on anyway as you are just intrudcing them un-necisseraly into the electrical system.

the figure from GN3 is 0.05 as that is the will ensure that the main protective device will rupture within 0.4 seconds assuming its a 100A hrc in a domestic property.( see appendix 4 of BRB)

I can see the argument for not bonding the gas, but would personally insist that a plumber installed a short section of copper to provide main bonding point. After all water will conduct, the palstic pipe just makes it an insulated conductor.

why put a bond on a short lenght of copper and bond that?
You made the statement that water can conduct but its in an insulated PVC pipe. For the water to conduct the fault current has to pass trough the insulated pipe in the first place. why put a bit of copper in the system. you are only extending the electrical system and therefore increasing risk.

 

[Spudnik]

The gas must still be bonded as its continuous throughout the house and wont be in plastic.

It also says (somewhere) that IF the installation is metal and the incoming is plastic, then it should still be bonded.

 

[zupos40]

Zupos just read the post

If the incomming supply of both Gas and Water to the istallation are plastic then no need to bond as thay are insulated. I would not put a bond on anyway as you are just intrudcing them un-necisseraly into the electrical system.

the figure from GN3 is 0.05 as that is the will ensure that the main protective device will rupture within 0.4 seconds assuming its a 100A hrc in a domestic property.( see appendix 4 of BRB)


Sorry typing error slipped in too many zero

 

[scotsparky]

The gas must still be bonded as its continuous throughout the house and wont be in plastic.

It also says (somewhere) that IF the installation is metal and the incoming is plastic, then it should still be bonded.

If there is continuous metal pipework in the house it should have a bond on it agreed !

how i read the post was it was a plastic incommer and plastic pipework apart from short lenghts to the radiatos. (like my house) In this case why bond everything as you are just introducing it to the electrical system. As there is plastic pipework then there is no earth path so no fault current. If however its only a short lenght of plastic puipework used to get round tight corners i would consider a little cross bond.

 

[markythesparky]

This is how i understand the regs:

If the incoming services are plastic and the pipework inside is completely plastic then no bonding is required.

If the pipework inside has metal parts, then the 0.05ohm rule applies (to extraneous and expose metal parts within areas of special locations and if not using RCD's) and then should be bonded if the reading is above this level. This being that above this level there could be a dangerous potential difference because of the high resisitance between pipes. If a lower resistance than 0.05 is read then this would be unlikely to cause a dangerous potential difference.

I stand to be shot down in flames though!

 

[scotsparky]

nearly there

If there was no potential difference the pipework would be live though.
What you want is a low earth path creating a very high fault current and so ensuring the overcurrent protective device will blow in time. The ESC and other agree on 0.05 as this will cover a 0.4 disconnection time on a 100a HRC will will be about the largest you will get in a domestic property.

 

[Richard3009]

Whatever happens i always run the cables in regardless, plus the gas should be bonded anyway.

Yep I would just install them and coil em up nearby at both ends , better to have and not need than vice versa after the plasterer has gone, lends for a better nights sleep.

 

[sparks1234]

The gas must still be bonded as its continuous throughout the house and wont be in plastic.

It also says (somewhere) that IF the installation is metal and the incoming is plastic, then it should still be bonded.

Explain why the gas WOULD not be in plastic, matey has already said they are in plastic