Megger X1 PEFC readings

[watoo watoo]

Megger X1 - anyone getting a vastly higher PEFC reading (2ka more) on 2 wire no trip, than PEFC on 3 wire

 

[davesparks]

It's not unusual to get a higher reading on a low current loop test than on a normal loop test and therfore the calculated fault current will be lower.

This has been referred to as 'RCD uplift' by some people as it can be the result of impedance through an RCD though the same problem can occur with low current tests when there is no RCD in the circuit.

This is one reason why a high current loop test should always be used whenever possible.

 

[watoo watoo]

It's not unusual to get a higher reading on a low current loop test than on a normal loop test and therfore the calculated fault current will be lower.

This has been referred to as 'RCD uplift' by some people as it can be the result of impedance through an RCD though the same problem can occur with low current tests when there is no RCD in the circuit.

This is one reason why a high current loop test should always be used whenever possible.

thought maybe new megger X1 may need a software update , purchased today but calibration sheet was april 23 . done same test on MFT 1711 and both were similiar readings, however rcbo tripping on no trip low on 1711 crabtree starbreaker i always seem to get them tripping, i reverse earth in phase and phase in earth socket on megger and test runs ok , no problems on new X1 just the unusually high PEFC

 

[newfutile]

Swapping line and earth can’t be a good idea , my Kewtech would refuse to test if it thinks over 50 volts on the cpc

 

[timhoward]

IMHO this is the best way to get accurate two-wire (high current) loop test data when the circuit is protected by an RCBO or RCD.

And here's the quick graphic I made for my assistant to explain why it works:

I regularly use this to get a loop test at a light switch using a 1553 (which has no 2 wire no-trip test)
You just have to remember to take the link out!

 

[newfutile]

I see what you mean now , i think i read it as swapping the leads in the meter, would it not be better to conduct and R1+R2 then add it to ZE?