Low Zs on TT puzzle

[dunny123]

I have measured the RA of a TT supply to be 56ohms (using loop tester method Ze). When I measure the Zs of a socket on the ring final (with a measured R1+R2 0.33ohms) , It gives a Zs of a mere 1.2ohms. Similar on other circuits. If I were to use the Zs=R1+R2+Ze I would get a calculated value of 56.33ohms, so why an i getting such low Zs ?? (and its not parallel paths, I have tried removing the bonding. Could it be possible that the supply is actually PME ?

 

[Adam_151]

You shouldn't be removing bonding with the supply live

And It'll be a parrallel path that you've missed... immersion heater or central heating cpc probably

edit: typo fixed

 

[ricicle]

Were all appliances disconnected/unplugged when you performed the Zs test ?
Did you IR test the circuit ?

EDIT:Too slow

 

[dunny123]

IR tests > 200M. Doubt its the water supply path as it enters property in plastic ! But yes it could have been an appliance still connected, I'll double check !

 

[RF Lighting]

Paralell path through the boiler spur to the gas pipework would be my guess.

As long as the installation is suitably protected for the actual Ze, then having a lower than expected reading is nothing to worry about.