Bonding

[pete1721]

hi there im just in the process of doing sum refurb works in a house and bringing it up2 scatch, ive put new cu in with 25mm tails etc but the bonding is guna be a nightmare to upgrade to 10mm is there anyway i can get away with using the 6mm bonding that is already there?

 

[AWD]

what type of supply system is it?

 

[Octopus]

Are you talking about main/earth bonding or equipotential bonding?

Is it TNS, TNCS or TT?

Main bonding TNS and TNCS should be 16mm, TT you may "get away" with 10mm

Keeping 6mm IMHO is a definite No No

Equipotential bonding should be 10mm but also take a read of 131.8

 

[pete1721]

hi lads yea the main earth is 16mm and its a TNS system!! looks like im just guna have to upgrade to 10mm bonding then

 

[Octopus]

hi lads yea the main earth is 16mm and its a TNS system!! looks like im just guna have to upgrade to 10mm bonding then

Have you read 131.8?

 

[pete1721]

no i have not read it what does it say? lol

 

[telectrix]

if you measure the main bonding conductors from MET to service clamp and get 0.05ohms or less, you may have a case for leaving the 6mm as is if major disruption to decoration, tiles, laminate floors etc., is necessary.

 

[electromonkey]

if you measure the main bonding conductors from MET to service clamp and get 0.05ohms or less, you may have a case for leaving the 6mm as is if major disruption to decoration, tiles, laminate floors etc., is necessary.

If there is a reading of 0.05 ohms, how long would it take (roughly speaking) under "normal" conditions for the cable to become unsafe?

 

[telectrix]

the cable has to carry the pefc for less than 1/2 second, assuming disconnection times are met. unless the EFLI is very low, 6mm can handle that witrhout degradation.

 

[pete1721]

cheers guys ill get on it on monday

 

[yellowvanman]

There is also an argument that if the 6mm is not showing any signs of damage/overheating then its Ok to keep that!

 

[telectrix]

i agree^^^ providing good connections and a good low ohms reading.

 

[Johnny-G]

I agree too, so does my most recent assessor, especially if you can prove that 6mm is sufficient by using the adiabatic equation.

 

[telectrix]

good point^^^. forgot about that. too interested in my beer.

 

[Johnny-G]

At least you've got your priorities right, it is Friday after all