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Is it my imagination or is this EICR a little odd?

Chris Pearson

Last week I had a look at a property which is up for auction, more as a matter of curiosity than a serious investment, but it is charming and if only I were 10 years younger!

The EICR was published today. It wasn't a drive-by (only at 70 mph mind 'cos there is a speed camera right beside the house on the M27) because the stickers, dated 2020 were on the DBs (peak and off-peak).

The estimated age of the installation is 35 years, but the DBs looked very modern - all RCBO and clean.

TN-C-S aerial supply. Ze was given as 0.31 Ω. So why in the table below do some of the Zs add up, and some not?

Circuit R1+R2 Zs R1+R2+Ze Discrepancy
Lights down 0.99 1.79 1.30 0.49
Lights up 1.86 2.36 2.17 0.19
Sockets down 1.42 2.02 1.73 0.29
Sockets up 0.66 1.32 0.97 0.35
Cooker 0.83 1.63 1.14 0.49
Immersion heater 1.12 1.46 1.43 0.06
Cooker 0.75 1.06 1.06 0.00
Shower 0.44 0.89 0.75 0.14
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  • So why in the table below do some of the Zs add up, and some not?

    My guess is "Zs" has been measured with a loop tester on a non-trip setting (while Ze was done on high current, and R1+R2 with a simple Ohm meter). My old megger installation tester very often reads a couple of a tenths of an Ohm high on no-trip (not fruit machine exactly, it's often reproducible, and within published specs of course).

      - Andy.

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  • So why in the table below do some of the Zs add up, and some not?

    My guess is "Zs" has been measured with a loop tester on a non-trip setting (while Ze was done on high current, and R1+R2 with a simple Ohm meter). My old megger installation tester very often reads a couple of a tenths of an Ohm high on no-trip (not fruit machine exactly, it's often reproducible, and within published specs of course).

      - Andy.

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