water and gas bonding

[panny300]

if a consumer unit is being replaced,and the tails and main earth uprated.
do the earths to the gas and water have to be upgraded,or can they be left as they already are i:e 4mm (or is it 6mm?)
or if there are no earths on water and gas,are they ok if certain continuity readings are met.

 

[PrenticeBoyofDerry]

If there are no water or gas pipes, what can you bond to, unless you have oil pipes.
The CSA of your mains earth will be dictated by the type of supply and the CSA(cross sectional area) of your Live and Neutral supply conductors.

 

[ColJack]

If there are no water or gas pipes, what can you bond to, unless you have oil pipes.

misread that one then?
said "no earths on the water and gas".. not "no water and gas..."

 

[bongos]

What is the supply type - TT, TN-S or PME?

25mm tails, 16mm main earth? Or somthing else?

if there are no earths on water and gas,are they ok if certain continuity readings are met.

You should connect protective bonding to the water/gas supply.

 

[panny300]

thanks for the replys. seemed simple question when i wrote it.
the bonding to the gas and water is the original 4mm or 6mm earthing,and the old consumer unit is being replaced by a new one.
if the tails and main earth are being upped to 25mm and 16mm.does the 4mm bonding have to be upped to 10mm,i know it should,but does it have to be.
if there was no bonding to the water and gas, can they be left with no bonding
as long as they meet certain continuity tests?

 

[ColJack]

ANY electrical work involves the requirement for a sparky to check and install the main bonding if it is missing, so no, you can't just leave it off if it's not already there..

you're best off upping the bonds to the required size as well.. if it's a short run then it's failry easy, if it's a long run, then it's unlikely that 4mm or 6mm will meet the required resistances anyway..

 

[panny300]

thanks coljack.
now you have opened up more questions.if 4 or 6mm won't meet requirements.does that mean the hundreds of thousands of households that still have 4mm bonding over long runs are'nt safe?

 

[skenk]

Not necessarily but they don't comply with current regulations

 

[GaryMo]

If it's deemed that 6mm² protective bonding conductors are adequate then you'll be limited to around 16 meters.

Have you any idea what your supply type is (PME, TN-S or TT)?

 

[panny300]

thanks again,but that was my original question,i know they would not be up to current reg,s but can the 4mm be left in place if the consumer unit has been renewed and the tails and main earth have been upped to 25mm/16mm

garymo,could you please explain what difference would it make on the type of supply

 

[GaryMo]

PME - you would require 10mm² bonding conductors.

TN-S and TT - you can calculate the size of the earthing conductor via the adiabatic equation and size your protective bonding conductors from there.
eg calulated minimum size of earthing conductor is 10mm², a 6mm² PEB conductor would suffice.

If bonding conductors are incorrectly sized then they would need replacing before your consumer unit is changed.

 

[Spark123]

With the exception of PME the minimum size for a PEB is 6mm.

 

[bongos]

i know they would not be up to current reg,s but can the 4mm be left in place if the consumer unit has been renewed and the tails and main earth have been upped to 25mm/16mm

If the consumer unit has been replaced then the bonding conductors should have been brought up to existing regs with the sizes stated above. You're right in saying that there will be lots of houses in the UK without the correct size bonding conductors. This is not a problem per se as the regs are not retrospective. However, when they have the CU replaced then the bonding will have to be uprated to the exisiting regs.

garymo,could you please explain what difference would it make on the type of supply

Have a look at different supply types here. The relevance of your supply type is that in TN earthing arrangements the earth fault loop impedance is much lower than in a TT installation, so as more fault current can flow in a TN system you would require a larger bonding conductor.