bonding gas and water how do you work out when to go up from 10mm to 16mm and so on

[chopper]

were currently doing a job in massive old pub whats going to be a libary, my gaffer says put 10mm bonding to gas and water but how do you actually work out what size is required

 

[Sparky Ninja]

Re: bonding gas and water how do you work out when to go up from 10mm to 16mm and so

By selection from BS7671

Section 544

 

[Deleted member 26818]

Re: bonding gas and water how do you work out when to go up from 10mm to 16mm and so

It depends on the earthing system, the size of the main earth and the size of the supply neutral conductor.
With TT and TN-S, you determine the size required for the main earth using the adiabatic equation, then bonding conductors are half the CSA of the calculated main earth CSA, but no smaller than 6mm².
With TN-C-S, both the main earth and any bonding conductors are sized according to table 54.8 in BS7671, with the minimum being 10mm².

 

[chopper]

Re: bonding gas and water how do you work out when to go up from 10mm to 16mm and so

ok nice one its having a new mains room so i assume the yeb will install a tncs system

 

[chopper]

Re: bonding gas and water how do you work out when to go up from 10mm to 16mm and so

just to add to this, i have just finished a apprentiship and i have never been taught about this, we do mainly houses so we allways install 10mm, but i just like to know for my own knoledge

 

[Sparky Ninja]

Re: bonding gas and water how do you work out when to go up from 10mm to 16mm and so

just to add to this, i have just finished a apprentiship and i have never been taught about this, we do mainly houses so we allways install 10mm, but i just like to know for my own knoledge

Surely you would have covered sizing of protective bonding conductors at college?
If you havn't got any course notes or reference I am sure we can find something.

 

[IQ Electrical]

Re: bonding gas and water how do you work out when to go up from 10mm to 16mm and so

just to add to this, i have just finished a apprentiship and i have never been taught about this, we do mainly houses so we allways install 10mm, but i just like to know for my own knoledge

Do you not have the On-Site Guide?

Page 27 onwards has it covered.

 

[chopper]

Re: bonding gas and water how do you work out when to go up from 10mm to 16mm and so

after thinking about what i said, we did get a breif lesson i remember the tutor saying bonding should be half size of the neutral, after just looking in regs it does say this but if you have any notes or links that would be great

why is it half the neutral though and not half x a phase presume sometimes the neutral is different sizes on 3 phase some time, i not had much experience on 3 phse

 

[mb706154]

Re: bonding gas and water how do you work out when to go up from 10mm to 16mm and so

lol
olo
lol

 

[ezzzekiel]

Re: bonding gas and water how do you work out when to go up from 10mm to 16mm and so

lol
olo
lol

not sure what this guy is studying

 

[malcolmsanford]

Re: bonding gas and water how do you work out when to go up from 10mm to 16mm and so

after thinking about what i said, we did get a breif lesson i remember the tutor saying bonding should be half size of the neutral, after just looking in regs it does say this but if you have any notes or links that would be great

why is it half the neutral though and not half x a phase presume sometimes the neutral is different sizes on 3 phase some time, i not had much experience on 3 phse

Read post 3 and Spinlondons excellent post, in a TNC-S the size of the Main Bonding conductor is proportional to the size of the incoming neutral and is explained in table 54.8 of the regs.

In a TT TN-S system the Main Bonding conductor is sized as minimum to be half the CSA of the Main Earthing Conductor, and must exceed 6mm.

The Main Bonding Conductor is sized for a TNC-S system on the Neutral conductor because it is the PEN conductor ( see the definitions in section 2 of the regs)

 

[malcolmsanford]

Re: bonding gas and water how do you work out when to go up from 10mm to 16mm and so

lol
olo
lol

That is a totally inane post.

The lad is learning and asking questions on here after completing his training, and by posting that drivel as taught him absolutely nothing, except perhaps the merit of your help.

I have to assume you know everything by now and deem this lads question beneath you, if that is the case, perhaps you will refrain from posting such in-depth replies to subjects that are obviously beneath you.

As you have posted just 15 times in 3 years perhaps your best off as lurker status, and leave replies to peoples questions to those on here that wish to help them

 

[SPARTYKUS]

Re: bonding gas and water how do you work out when to go up from 10mm to 16mm and so

Hi Chopper, another thing to watch is distance from MET; for example if you're up to 27/28 metres with your bonding 'run' then its at the limit of its required resistance ( <0.05 Ohms ). In this case (if it was,say,35 metres) then you should use 16mm2.

Is that right btw re: the 1/2 the neutral size just for TNCS? Isn't it for TN systems. Or am I wrong again!

 

[IQ Electrical]

Re: bonding gas and water how do you work out when to go up from 10mm to 16mm and so

Hi Chopper, another thing to watch is distance from MET; for example if you're up to 27/28 metres with your bonding 'run' then its at the limit of its required resistance ( <0.05 Ohms ). In this case (if it was,say,35 metres) then you should use 16mm2.

Is that right btw re: the 1/2 the neutral size just for TNCS? Isn't it for TN systems. Or am I wrong again!

Yes, a bit of confusion, it's sized in PROPORTION to the SUPPLIER'S neutral conductor (not the tails) on TN-C-S systems, and there isn't actually a 0.05 Ohm resistance limit on main protective bonding.

 

[telectrix]

Re: bonding gas and water how do you work out when to go up from 10mm to 16mm and so

Yes, a bit of confusion, it's sized in PROPORTION to the SUPPLIER'S neutral conductor (not the tails) on TN-C-S systems, and there isn't actually a 0.05 Ohm resistance limit on main protective bonding.

and that's a new one on me. is the 0.05 only applicable to TN-S then, IQ?