PIR today

[chrish_1977]

Hi everyone in advance, carried out a PIR today, nothing special 8 circuits on a dual rcd board, supply is TN-S. Done a Ze at service head and got 0.10 ohms (very good i thought). However here is my problem, the radial for the boiler and the ring circuits came out at 0.90 approximately. R1+R2 are 0.23 approximately and length of run is about 15-20 metres.

It has a crabtree starbreaker board ( with the enclosed busbar) has anyone else had high readings when testing or is it just me.

Checked all screws for tightness and were all ok, even checked all sockets. Couldn't find anything obvious

Thanks in advance

Chris

 

[telectrix]

a bit of an effect caused by the MCBs, esp if you are using the no-trip loop test. as long as the readings are below the permitted max. ( which at 0.9 ohms is , for a 32A type b and all lesser rated MCBs). job's sound.

 

[Des 56]

Have you measured the impedance of the mcb

 

[telectrix]

alternatively you could derive Zs from Zs= Ze+ ( R1+R2 ). your continuity readings look spot on. (a 10m radial in 2.5/1.5 should give around 0.2ohms.)