reg 132.16 - how flexible is it? :)

[spark 68]

Am I just picking out part of the reg?

I didn't mean you specifically Brman, but you have take the reg as whole, and it does not really get more explicit than this particular reg, it specifically states what is required.

I know you are playing devils advocate here

 

[huntos33]

I thought this was one of the clearer regs to be honest, as you cannot just pick out a part of the reg that suits you, or more correctly the tight arse customer, you have to take the reg as a whole.

Whether we like it or not, Main Bonding is part of the ADS system.

I usually just include the bonding as part of my quote if it is required, I tell the customer this has got to be done regardless, and if they don't agree then I don't do the work.

This is how I aproach things no bonding no 30ma no work, i maybe wrong but im newly on my own and dont have a big boss man behind me anymore so its my --- on the line.

 

[JUD]

Ok, before I start I should say that I normally assume that 132.16 means that bonding and earthing should be ok before ANY additions or alterations take place. However I just wanted to explore what the reg actually means.

So....
"no addition or alteration.... shall be made... unless it has been ascertained that the rating and the conditionn of any existing equipment, including that of the distributor, will be adequate for the altered circumstances. Furthermore, the earthing and bonding arrangements, if necessary for the protective measure applied for the safety of the addition or alteration, shall be adequate"

As I read this that means you are only concerned whether the earthing and bonding is ok for the addition, not the whole system.
So, lets take an example: Adding a socket spur to a ring at an existing socket where the Zs is say 0.8. Lets also say the Zs at the origin is 0.2.

Using those figures I get a PEFC for the installation of 1.15kA (ie. 230/0.2) and a PEFC at the modification of 287A (230/0.8).
So, assuming a 100A BS88-2 main fuse with a 1.15kA PEFC I get t = 0.4s ish and the adiabatic gives me main earthing conductor CSA = 6.3mm2 to protect the whole system.

However if I am only concerned about the addition then my PEFC is 287A through a 32A type B MCB giving me a CSA= 0.8mm2!!

So, leaving aside arguments about common sense and making sure the whole system is safe, if the customer refuses a earthing upgrade am I allowed to make this alteration and sign it off if say there is a 4mm2 earthing conductor present? Obviously with a note that there is a C2 fault on the cert!

This goes against what I thought was allowed so I am very interested to hear other views and why.....

I get different results...

You have used the wrong k value. The k value for a conductor not incorporated in a cable (assuming it's not) is 143 not 115.

This is what I get for the Earthing conductor

PEFC = 1150A
k = 143
t = 0.4s

S = √(I²t) ÷ k
S = √(1150² x 0.4) ÷ 143
S = √529000 ÷ 143
S = 727.32 ÷ 143
S = 5.1mm²

You don't say in your example if this is a TN-S or TN-C-S supply. If TN-S then the csa of the main protective bonding conductor should be at least half that required for the Earthing conductor and not less than 6mm². If TN-C-S then it should be based on the size of the supply neutral conductor (544.1.1).

 

[Octopus]

I do like these threads!

 

[brman]

I do like these threads!

so do I, that is why i started it

 

[brman]

I didn't mean you specifically Brman, but you have take the reg as whole, and it does not really get more explicit than this particular reg, it specifically states what is required.

I know you are playing devils advocate here

ok, you got me there :lol:

Right, so universal disapproval of my new interpretation of the reg then! I guess I better stick with the old way then!