cpc csa

[the pict]

Am I right on this, as far as I can fathom the regs state that the CSA of the CPC should be equal to the live conductors but T&E are not required to conform, so does that mean if a circuit is wired in singles in plastic conduit then the rule applies, but if wired in steel conduit and the conduit is earthed then the cpc size can be reduced accordingly, and yes I understand that the appropriate tables will provide this info but what the take on this in practice
Pict

 

[telectrix]

when wiring sinles in conduit and trunking, it is general practice to use the same size cable for cpc. the T/E thing is more to do with the manufacture of the cable, i.e.use the least amunt of copper as possible to still comply. (and makes the cable nice and fla)t

 

[malcolmsanford]

Regulation 543.1.3 and the Adiabatic equation is all you need to work out your CPC sizes.

 

[i=p/u]

well i say why 2.5 for earth if you can get away with 1.5

 

[i=p/u]

ok was my tutor said it

 

[scotsparky]

i agree ipoveru! oops wrong formua. Easier to pull in as well. When you get into bigger sisies best to double check but general rule is half for CPCs.

 

[the pict]

You see where I get mixed info is that the cpc resistance value is given as 1.67 times the L&N but also that the CPC should be the same ada and 543 aside that 2 conficts, and I mean we have to use T&E as it's supplied and we are told it'ds compliant but if you calc it out as malcolm has said you will invarably get a cppc greater than T&E
Pict
PS Scotsparky are you corner,garthland or bull man

 

[amberleaf]

I would like to Thank the Forum Member’s . for putting up with Old Amber. Thank You .

Later Thinking . ( Earthing can take us down many !! Scenarios’ . Yeah

● What does the Very first line of ( 543.1.1. ) Actually Mean . 2392-10 2391-10 .. Understanding Matter’s Particular Attention to the Six Words between the First Two-Commas . ↔ ( Other than a Protective Bonding Conductor ) ◄◄
( Hint : 543.1.1. Refers – Earthing and “ Not “ Bonding ) ….. Main Earthing Terminal 16mm2 .
Let’s not mix up the 16th Ed - ? Equipotential Bonding Conductor . ( 17th Edition - Main Protective Bonding Conductor ) Gas / Water 10mm2
( Room for Though ) 16mm2 is the Recommend minimum Size for the Earthing Conductor )
( You must not use a BS-951 bonding Clamp . DNO – Constant Spring Force Clamp may Only be Used by the DNO – is Responsible for the Cable . )

543.1.1. basically . saying you can do 1 of 2 things .
(i) Either select the Earth from table 54.7 . which means 16mm2 Earth for Line Conductors up to 16mm2 . ( S ≤ 16 )
(ii) Use the Equation from 543.1.3. to Calculate the Earth Size based of Fault Current & the Time it takes the Protective Device to Operate .

(i) Calculated in accordance with Regulation 543.1.3. or
The Cross-sectional area . where Calculated . shall be met “ Not “ Less than the value determined by the following formula or shall be Obtained by reference to BS-7454 :

(ii) Selected in accordance with Regulation 543.1.4.

100A :- Cable Sheath Earth ( TN-S system ) Earthing & Main Equipotential Bonding arrangements . based on 25mm2 Tails & selection from table 54.7.
( an Isolator is “ Not “ always Installed by the Electricity Distributor . DNO. )

100A :- PME ↔ supply ( TN-C-S ) Earthing & Main Equipotential Bonding arrangements . based on 25mm2 Tails & selection from table 54.7.

** 100A :- No earth provided ( TT system ) Based on 25mm2 Tails & selection from table 54.7. ( Double Pole )
( Manufacturers recommendations should be sought with regards to Connections to Earth Electrodes )

( Taking Priority . if the Network Operator has other Demands regarding Earth Size then they should take Priority )
Example : -

● As for any Installation ! (i) Source of Supply T/??? . (ii) Source Earth . (iii) Any ? Exposed Conductive Parts . ( Design ! Electrical Installation(s) )

* Cable Protective Conductor … ( Armour / Sheath ) ??
( 131.8 . Rating chosen to be Less than or Equal / to Current Capacity Cables )
( for the Younger Member’s . at random !! Design ! Electrical Installation(s) ( C.C.C. ) ↔ Current Capacity Cables . tables 4D1A / Example .

Points of Observation . Yeah
I feel that a Lot of People need to get to Grips with Overcurrent . Two Instances it can Occur ( Overcurrnts ! Fault Currents ! )
- The Higher the Impedance the Longer it takes for the Fault Current to Build .
2392-10 * 100A – BS-1361 will Clear a Fault in Less than ( 0.1 sec ) at a Fault Current of Less than 2000 Amps .
2392-10 * The Disconnection Time on the Main Intake Fuse is there to Protect the Cable not the Person .

Prospective Fault Current :
The Maximum Possible Fault Current .
The value of Fault Current at a Given Point in a Circuit resulting from a ( Fault of Negligible Impedance ) between Live Conductors’ & a Circuit Protective Conductor ( Earth Conductor )

Prospective Short Circuit Current :
The Maximum Possible Short Circuit Current .
The value of Short Circuit Current at a Point in a Circuit resulting from a ( Fault of Negligible Impedance ) between Line Conductor & Circuit Neutral Conductor . or between Line Conductors of Different Phases . ( again I use the Word Neutral Conductor . Live Conductor )

** p/50 . Table 41.5 – BS-7671
Note 2 : which requires the Résistance of the Electrode to be Below 200Ω ( Above that Reading is Classed as Unstable )
It should be a Low as Possible in all Cases .
( Point to Note ) 21Ω is the Maximum Résistance Stated by the Distributor . DNO . Back at the Supply Transformer ( Definition : Their Electrode(s) )

It’s how the 17th Edition is Interprereted .

I did get this on my 17th Edition . ( Lightning Protection )
Is a Disconnectable Link needed between ( MET ) & Lightning Protection ( Your Call ) (T)

The needs to be Facility to Insolate the Lightning Protection System . Electrical Installation Testing . ( Yes )

Old Amber is on One . again . Some light Reading .

 

[amberleaf]

Helping to push it over the Edge . RCD .
More Appliances than Normal / Combination of them may push the Leakage over the Limit .

Very Basic’s .
One Possibility . Often Overlooked ( Faulty RCD )
Reason Test Button :- RCD Simulates a Imbalance Current . Several Times the Trip threshold .
( Any Method isn’t Bulletproof with RCDs ) ◄

( The Earthing plays an Important Part in a RCD Life . on any Installation(s) . Yeah ( CPC )

What’s going for the RCBOs . They ensure good Discrimination . MCB/RCD – Only the Affected Circuit is Taken Out of Action .

 

[Deleted member 26818]

The requirement for the CPC to have a minimum CSA of 2.5mm² is for when it is not an integeral part of a cable, such as with T&E.

 

[Sparky Ninja]

The requirement for the CPC to have a minimum CSA of 2.5mm² is for when it is not an integeral part of a cable, such as with T&E.

What requirement are you referring to?

Regulation 543.1.3 and the Adiabatic equation is all you need to work out your CPC sizes.

That's my opinion also.

 

[Deleted member 26818]

That will be the one in Regulation 543.1.1.

 

[Sparky Ninja]

The requirement for the CPC to have a minimum CSA of 2.5mm² is for when it is not an integeral part of a cable, such as with T&E.

Oh ok. Would have helped to mention the 'not formed by conduit, ducting or trunking' bit.

 

[Deleted member 26818]

I don't know, the OP seems to think that a reduced CSA is allowed if the conductors are in earthed steel conduit as opposed to PVC conduit?