R!+R2 Question

JUD · Apr 26, 2012

farmelectrics said:
Done the above test many times jud and tried the tests with and without flying lead to back boxes with the flying lead connected you get a much lower reading now what is that telling me it's picking up other paths or have I been doing these tests all wrong

This is the resistance path with the cpc and conduit connected at the earth bar along with the line conductor

This is the resistance path with the line and cpc connected together in a connector block and independent of the earth bar

Farmelectrics · Apr 26, 2012

Jud not disagreeing with your diagrams but the db is earted the conduit is connected to the db therefore the flying lead from back box which is connected to the conduit is earted ie from db so if you don't disconnect the eart to the back boxes you are picking this paralel earth up honest

JUD · Apr 26, 2012

Yes but the resistance measured by the meter needs a loop from one test lead to the other.

Because the link between the cpc and conduit is broken at the DB, the conduit is no longer part of the loop.

Imagine what would happen if applied a current to the line conductor in the second picture. It can't travel through the conduit as it isn't part of the circuit. The current would travel down the line conductor, through the link and back down the cpc to the origin.

spark 68 · Apr 26, 2012

Hi Jud,

I would agree with you if not for the links to the back boxes, which is connected to the CPC at each accessory. if I have read the Op correct.

This effectively places a length of conduit in parallel with the CPC, between each flying lead that is still connected.

I hear what you are saying, RE: disconnecting from the Earth bar as this would normally remove the conduit from the test readings, but in this case the conduit is still connected at multiple points along the way, via each flying lead.

Farmelectrics · Apr 26, 2012

Spark68 thank you

Farmelectrics · Apr 26, 2012

Jud I respect your views as a fellow electrician just had issues with this type of installation in the past and the correct way of testing

JUD · Apr 26, 2012

DOH!! :frown2: :73:

Been a long day

Des 56 · Apr 26, 2012

Whilst reading this debate, I was glad the R1+R2 question reached a satisfactory conclusion

Now I would like to make another point relevant to this thread,which that I was trying to resist making till then

As far as the little I know,the question of the R1+R2 on a completed conduit system should not need discussing:tounge_smile:

If that figure was required it should have been taken before any accessories were fixed and the fly leads installed,so there