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

 

[Wilko]

I think reg 542.4.1 applies : "in every installation a met shall be provided to connect the following to the earthing conductor - CPCs - protective bonding conductors ... etc"

My 20p worth : the existing arrangement is not in accord with 542.4.1 and so I would give it a C3, as it is not unsafe (for you to confirm with testing?) but it would be an improvement to comply with regulations.

I'm not expert in this one, and others please feel free to jump in

 

[HandySparks]

I say that as long as the water pipe (if extraneous) is connected to the MET by conductors that comply along the whole route with the requirements of protective bonding conductors, it doesn't matter if they go via one or more other terminals.

542.4.1 doesn't say that all CPCs, protective bonding conductors, etc. have to be connected directly to the MET. In fact most CPCs won't be connected directly to the MET.

 

[Pete999]

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

Hi akwoody2 have the Mods got your profile correct because you are down as DIY, I have to ask because if you are actually a DIY Member do you think you should be doing EICRs?

 

[akwoody2]

Hi akwoody2 have the Mods got your profile correct because you are down as DIY, I have to ask because if you are actually a DIY Member do you think you should be doing EICRs?

Hi Pete,

I'm a fully qualified electrician, not to sure why I'm down as DIY. Maybe something to do with me not putting my qualifications in yet?

Do you have an opinion on the bonding to the water?

 

[Pete999]

Hi Pete,

I'm a fully qualified electrician, not to sure why I'm down as DIY. Maybe something to do with me not putting my qualifications in yet?

Do you have an opinion on the bonding to the water?

Well it is connected to the MET in a round about way, without seeing the job it's quite hard to form an opinion, as for your profile, best you get it updated, the wrong,or no info can lead to incorrect or sometime abusive answers, the non filling out of profile info is a pet hate of mine, I have posted before requesting correct profile info is a must, but quite rightly you can't make people provide info if they don't want to.

 

[bigspark17]

Hi akwoody2. What size/type is the submain cable to the subboard? And is the incoming supply pipe metal?

 

[akwoody2]

Hi akwoody2. What size/type is the submain cable to the subboard? And is the incoming supply pipe metal?

16mm 4 core SWA, armoured being the cpc. Incoming water is copper

 

[akwoody2]

Well it is connected to the MET in a round about way, without seeing the job it's quite hard to form an opinion, as for your profile, best you get it updated, the wrong,or no info can lead to incorrect or sometime abusive answers, the non filling out of profile info is a pet hate of mine, I have posted before requesting correct profile info is a must, but quite rightly you can't make people provide info if they don't want to.

I'll get it done for you tonight Pete!

 

[Pete999]

Thank you Mate, I'

I'll get it done for you tonight Pete!

I'm filling up need to get a tissue lol well done

 

[Pete999]

16mm 4 core SWA, armoured being the cpc. Incoming water is copper

So is the amour acting as a cpc and bonding conductor

 

[bigspark17]

So is the amour acting as a cpc and bonding conductor

Well if you read the post its obvious it is being used as that at the minute! But incorrectly so, 16mm 4c has steel equivalent of 72mm which in terms of copper equivalent is inaquate in terms of being <10mm. I would back you up in a C2 observation on that observation.

 

[HandySparks]

What's the earthing system?

 

[akwoody2]

What's the earthing system?

TN-c-s Handy

 

[akwoody2]

Well if you read the post its obvious it is being used as that at the minute! But incorrectly so, 16mm 4c has steel equivalent of 72mm which in terms of copper equivalent is inaquate in terms of being <10mm. I would back you up in a C2 observation on that observation.

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

 

[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.