EICR question

[akwoody2]

Hi chaps,

This may have been asked before but i cant seem to find it when searching so im sorry if someone easily finds it.

Im currently carrying out a EICR at a commercial premises and the water is bonded from a sub DB and not the MET, its something that i understand needs to be noted but is it something that needs to be coded? If so what code?

Thanks

 

[bigspark17]

Find the csa of the armouring on data charts provided by manufacturers then divide by 8.8 to convert to equivalent copper csa conductor. Out of intrest how would you go about correcting this? Are you going to reroute/extend bond back to MET or add an additional cable to the EMT to and leave bond in place?

 

[akwoody2]

Find the csa of the armouring on data charts provided by manufacturers then divide by 8.8 to convert to equivalent copper csa conductor. Out of intrest how would you go about correcting this? Are you going to reroute/extend bond back to MET or add an additional cable to the EMT to and leave bond in place?

I'd run it back to the MET as it's not actually that far away

 

[akwoody2]

Find the csa of the armouring on data charts provided by manufacturers then divide by 8.8 to convert to equivalent copper csa conductor. Out of intrest how would you go about correcting this? Are you going to reroute/extend bond back to MET or add an additional cable to the EMT to and leave bond in place?

So by calculation you would need a 70mm 4 core to get the equivalent of 16mmcpc. How come we see so many sub mains being ran with the steel being the cpc if it doesn't comply?

 

[westward10]

So by calculation you would need a 70mm 4 core to get the equivalent of 16mmcpc. How come we see so many sub mains being ran with the steel being the cpc if it doesn't comply?

Because people don't understand that just because the armour has a large csa it isn't necessarily adequate to support bonding. Rule of thumb times your bonding size by 8 to get the required size of armour, GN8 has all the info. If you have a four core cable less than 50.0 it will be inadequate to support the minimum size of 10.0 bonding

 

[akwoody2]

Find the csa of the armouring on data charts provided by manufacturers then divide by 8.8 to convert to equivalent copper csa conductor. Out of intrest how would you go about correcting this? Are you going to reroute/extend bond back to MET or add an additional cable to the EMT to and leave bond in place?

The cpc also needs upgrading for the 100a supply to the sub board

 

[Wilko]

Putting on my student's tin hat, I'll give it a bash :

For bonding we are concerned about touch voltages and so the path must be comparable to the resistance of Cu and so we use resistivity ratios (>8). For use as CPC we use the adiabatic eqn and its k factors that include temp rise and thermal capacity of the materials. This gives a reduced steel requirement compared with bonding calcs and so SWA armour is often ok for CPC but not for bonding.

 

[HandySparks]

So by calculation you would need a 70mm 4 core to get the equivalent of 16mmcpc. How come we see so many sub mains being ran with the steel being the cpc if it doesn't comply?

They may be perfectly OK for a CPC, just not for bonding.

 

[davesparks]

So by calculation you would need a 70mm 4 core to get the equivalent of 16mmcpc. How come we see so many sub mains being ran with the steel being the cpc if it doesn't comply?

Because CPC size is calculated by the adiabatic equation and not by the equivalent conductivity method used for bonding. the CPC only has t carry fault current for a specified time which is limited by the fault protection device and so can be a lot smaller than the bonding conductor required on TNCS.

 

[davesparks]

The cpc also needs upgrading for the 100a supply to the sub board

The armour will be fine as the CPC, it almost always is up to something like 120mm I think from rough memory

 

[bigspark17]

The cpc also needs upgrading for the 100a supply to the sub board

What makes you ask this? Bonding and cpc requirements of swa armour are very diferent.

 

[akwoody2]

Sorry, a combination of me not following the thread correctly, reading it in my phone with a cracked screen and getting completely mixed up. Cpc is correct and won't need to be altered. As for the bonding it's not man enough so a recommendation will need to be put down

 

[Pete999]

Thanks. Out of interest how did you get to it being the equivalent of <10mm?

There is a comparison chart in the OSG
file:///C:/Users/Pete/Desktop/Electrical%202/SWA%20CPC.pdf

 

[Pat H]

Pete that's a link to the pdf copy in a folder on your PC desktop. So hopefully inaccessible to the outside world.
And I suspect admins will not allow a copy on the forum of any of its content due to copyright.

 

[Pete999]

Pete that's a link to the pdf copy in a folder on your PC desktop. So hopefully inaccessible to the outside world.
And I suspect admins will not allow a copy on the forum of any of its content due to copyright.

Oh sorry I thought I had posted a copy of the chart, can admin please delete

There is a comparison chart in the OSG
file:///C:/Users/Pete/Desktop/Electrical%202/SWA%20CPC.pdf

Admin can you please delete my reply