Existing Swa

[cliffed]

Relocating workshop to a new position,this requires Swa supply to be jointed to new position.
The original swa is a 10mm 4 core,using sheath as cpc,we are extending this.
It's also a 3phase /N supply.
I'm ok with this,but the problem I see is the main earth bonding requirements,spoken about this to the powers to be,but completely ignored & carry on with the installation,like to like of the orig workshop,what's your say on this.
The orig workshop,was updated & no one mentioned this before,the supply is most probably over 30 years old,& remote from main building in a trench.

 

[LeeH]

Earthing arrangement?

Any other services to it?

 

[Pete999]

When you say "you spoke to the powers to be" could you confirm who they are because I doubt very much the SWA armouring will be large enough for both Earth and bonding, not got any books available at present yo check the equivalent steel to copper comparisons. I am assuming there are other services such as water gas etc to the new workshop

 

[cliffed]

Earthing arrangement?

Any other services to it?

Yea steel girders,water incoming but plastic.

When you say "you spoke to the powers to be" could you confirm who they are because I doubt very much the SWA armouring will be large enough for both Earth and bonding, not got any books available at present yo check the equivalent steel to copper comparisons. I am assuming there are other services such as water gas etc to the new workshop

Agree

 

[cliffed]

Earthing arrangement?

Any other services to it?

Steel construction,water but plastic,existing earthing is tns

 

[westward10]

I know without looking the armour is inadequate to support bonding.

 

[Pat H]

The resistance of steel is much higher than copper so even a relatively small copper earth out performs a large steel wire armour. Assuming the original SWA steel was adequate for the earthing and bonding (ie a short SWA run) then it depends on how much further the cable is being extended.
Much debate on extending earthing bonding as you will find if you dig into the forums.

 

[cliffed]

I know without looking the armour is inadequate to support bonding.

So do I,but at the moment the earthing arrangement,remains as it was,I'm not happy with that,& the client doesn't wanna know,it was ok then back then etc...
Should be tt system,but who pays.

 

[bill01803]

Just make it TT

Customer pays

 

[Pete999]

So do I,but at the moment the earthing arrangement,remains as it was,I'm not happy with that,& the client doesn't wanna know,it was ok then back then etc...
Should be tt system,but who pays.

Your client should pay if he wants the job done, just because he deemed it OK before doesn't mean it is OK, you said you are not happy, your name and reputation will be on the line if you carry on without insisting on the right way to do thing, a reality check is needed.

 

[Richard Burns]

Effectively if you need to provide main bonding to extraneous conductive parts in the workshop, as it sounds as if you would for the steel constructional elements then the minimum csa for your bonding, if you have a small incoming supply for the installation, is 6mm² the effective copper csa of the supply cable SWA is 4.9mm².
This means that unless you can get a main bonding conductor that can cover the space from the MET to the point at which you are jointing the cable (does not sound likely in a trench) or to the workshop then you would have to provide a local earth rod and appropriate RCD protection at the workshop in order to have a compliant and safe installation.
This is what you need to communicate to your customer.

 

[bigspark17]

Just make it TT

Customer pays

Agreed

 

[cliffed]

Effectively if you need to provide main bonding to extraneous conductive parts in the workshop, as it sounds as if you would for the steel constructional elements then the minimum csa for your bonding, if you have a small incoming supply for the installation, is 6mm² the effective copper csa of the supply cable SWA is 4.9mm².
This means that unless you can get a main bonding conductor that can cover the space from the MET to the point at which you are jointing the cable (does not sound likely in a trench) or to the workshop then you would have to provide a local earth rod and appropriate RCD protection at the workshop in order to have a compliant and safe installation.
This is what you need to communicate to your customer.

Agree also,told all concerned about this at start of Job but no one is listening,the new swa is made into new TPN DB,MAIN SWITCH fitted & alive,this was done by another one of our sparks,who also knows about my concerns.
Quite a bit of work now involved in re-doing all works,if someone orders me to do it,in the long run I shall be testing & our company will be issuing a EICC schedule.

 

[westward10]

As a rule of thumb divide the csa of the armour (see GN8, Appendix B) by 8 to give you the related size for bonding purposes. The minimum size of a 4 core cable that will support the minimum size of 10.0 bonding is 50.0, if it is below this no calculation is required it is inadequate. Or work the other way and times the bonding size by 8 and find the size of cable armour which will comply in GN8, Appendix B.
Simples.