To high a readin

[KillerKlown]

Hi, One one of our dispensing machines I'm currently PAT testing has a 20-30m lead on it, connected to a 3 pin blue round plug. I have the adaptor thats needed. My question is, would the lenght of the cabel affect the earth reading? It's coming up at 0.21. I know some can be let go if it's 0.12 as it may not be the best earth contact you have with the probe. But is 0.21 acceptable taking the lead size into account?

 

[UNG]

The length of cable will affect the earth reading

 

[Richard Burns]

you need to know the csa of the cable and look up the per metre resistance of that size cpc multiply by the length of the cable and add that to your base 0.1ohm to get the allowable resistance reading. Even a 4mm cable 30m long will comply at .21ohm. you just have to think about voltage drop, if appropriate.

 

[MarkieSparkie]

See COP, Appendix vii, Table vii.1, for the nominal resistance of the appliance CPC. Identify the CSA of your CPC, multiply the resistance for a metre of that CPC (in mOhms) by the length of you appliance cable (in m) and divide by 1000 to get resistance of your CPC in Ohms. Subtract the resistance of the CPC from your measured earth continuity resistance, if the result is <0.1 Ohms your appliance has passed it's earth continuity test.