earth loop reading

[ian2799]

can anybody tell me why the earth loop impedance on a circuit should be a lot lower than r1 plus r2 reading i thought earth loop reading should equal r1 plus r2 plus ze

[ericmark]

You are correct Ze + R1 + R2 = Zs but R2 may have parallel paths which will reduce it's reading.
In real terms R1 + Rn is the more limiting factor as with RCD's on nearly everything the 5% volt drop will normally be what controls cable length.
All best Eric

[ian2799]

many thanks ericmark this makes perfect sense