High earth loop on bathroom light with fan?

whazza22 · Sep 30, 2012

Hi there

I was testing the earth loop on a bathroom light with the fan pull switch turned OFF (not double pole) and got a reading of 330 ohms.

When I turned the fan on, the reading was down to 0.60 ohms which is obviously ok.

Would this be due to the neutral not being switched from the pull switch?

Thanks

ExArmy · Sep 30, 2012

how is it wired up exactly? It won't be anything to do with the neutral, earth fault loop is just the resistance of live and earth

Silly Sausage · Sep 30, 2012

With the switch off, I reckon that you're measuring the loop resistance of the fan load, neutral and earth conductors.
Switch on, the Line conductor is in parallel with the fan load & neutral, so your Zs of 0.6 will be slightly less than if you measured it with the fan disconnected.

telectrix · Sep 30, 2012

all depends on where you are measuring at. if you're measuring at the fan switched L, then the fan switch needs to be on

whazza22 · Sep 30, 2012

I was measuring at the bathroom light between perm live, neutral and earth then between switch live, neutral and earth. Both giving a reading of 300+ ohms. The insulation resistance is fine.

The fan is wired directly from the light with a perm live, switch live, neutral and earth so the fan runs after light is switched off.

As soon as I switch the fan on, the readings are all fine. It's just when the fan switch is off so I'm assuming its because the neutrals aren't switched?