R1 + R2 test on SWA

[Ponty Massive]

Simples mate. You link live to armour at the each point, and thats your reading. As armadillo sparks mentioned, the only other option is a wander lead, and measure R2.

But surely that would be measuring an R2 that your not using? Using a wander lead is also measuring an R2 that isn't being used I.E the SWA?

 

[Ponty Massive]

As it is a TT system the chances are that your going to have to protect that sub main distribution circuit with an RCD as you will most likely not get a low enough disconnection of 1 second if it over 32 amps or 0.2 for under with just a normal MCB/FUSE. So for the Zs of the circuit you would put 500ohms if your using a 100mA RCD, and then test for times.

I normally would calculate R1 + R2 for a SWA cable that is utilising the armour as a CPC as such. using a wander lead, measure the R1 and then the Armour R2 and then combine it with the Ze to find the Zs.[/QUOTE]

I agree, but again wouldn't you be calculating for an R2 that isn't being used?

 

[Ponty Massive]

May be wrong but I would link live to armour at garage end and class that as R1/R2. The armour should be bonded at the supply end i.e. the house as that is where the associated protection for that cable is.

Why is this? Which reg?

Thanks

 

[malcolmsanford]

As it is a TT system the chances are that your going to have to protect that sub main distribution circuit with an RCD as you will most likely not get a low enough disconnection of 1 second if it over 32 amps or 0.2 for under with just a normal MCB/FUSE. So for the Zs of the circuit you would put 500ohms if your using a 100mA RCD, and then test for times.

I normally would calculate R1 + R2 for a SWA cable that is utilising the armour as a CPC as such. using a wander lead, measure the R1 and then the Armour R2 and then combine it with the Ze to find the Zs.[/QUOTE]

I agree, but again wouldn't you be calculating for an R2 that isn't being used?

What R2 are you not using, if you have a 2 core cable and armour CPC. ?

 

[truckster]

Why is this? Which reg?

Thanks

411.5.1

Had to look that up

As an example I had to go to a farm where the labourer had driven a tractor through the yard with the forks up, he snapped a 16mm split con overhead that it turned out was earthed at the barn end. The fuse had not blown and when I arrived I found the split neatly coiled up by the house still live!

 

[Ponty Massive]

What R2 are you not using, if you have a 2 core cable and armour CPC. ?

Just seems a bit strange having supply from DB1 and SWA tied at DB2.

Thinking about it logically however, as long as there is a path to earth for the fault current then it will work?

 

[Ponty Massive]

411.5.1

Had to look that up

Thanks WOuld have been more impressed if it was from memory !!!:wink5:

 

[lepoidm]

IMO the earth for the DB cicuit has to be taken back to the main board. The rod in the garage is is in addintion for final circuits in the garage. I would deffo run seperate earth.

let us know what you end up doing

 

[Blowcat]

I dont like the sound of this circuit. Why dont you in the house terminated the swa into a metal adaptable box using the earthings rings and then run a cpc from banjo back to the DB HOUSE CPC terminal. Then you have the circuit cpc connected as to normal practises.
If you cant get an R1/R2 the way it is now i would have thought that is a code 1 non compliance.

 

[LlandrilloSpark]

I suppose it's a matter of choice, Like Malcolm says his preference is maybe to use the Armour as cpc, some peoples is to run a single cpc, I prefer the seperate because it's how I was taught and it's what Ive always done

 

[Ponty Massive]

I dont like the sound of this circuit. Why dont you in the house terminated the swa into a metal adaptable box using the earthings rings and then run a cpc from banjo back to the DB HOUSE CPC terminal. Then you have the circuit cpc connected as to normal practises.

That's exactly what I have done.

Thanks all :flowers: