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Continuity - removal of resistances

Former Community Member
Former Community Member
Hello,


Does anyone know for certain why lamps have to be removed in a lighting circuit continuity test? I can understand why they are removed for an insulation resistance test, as they can give a false reading, but I have never found an explanation of why they are removed in a continuity test, it is just something you are advised to do, e.g. pages 103 and 104 of the On Site Guide have illustrations that show "lamps removed", but with no explanation.
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    I have not removed lamps in the new house installation I am working on and testing at the moment,  that's because they are LED downlights and there are not any removal lamps. 


    Those diagrams are now very outdated and it's time that the guidance is reviewed.


    I have tested the new installation with the LED downlights installed,  but not the dimmer switches having temporarily fitted plain rocker switches. 


    R2 testing with a wander lead is the  most accurate way of testing the circuit protective conductor continuity and is not affected by any installed lamps or dimmer switches. 


    Testing, R1+R2 with the lamps in is less accurate as the lamps give interconnections through them and the  neutral, but provides a polarity dead test, a high reading will indicate reverse polarity with a lamp in circuit. 


    I don't run the circuit from light to light as in the onsite guide diagrams , I go from switch to switch then take a twin and earth cable to the lights which can solve various installation and testing issues.


    Andy. 

Reply
  • 0
    I have not removed lamps in the new house installation I am working on and testing at the moment,  that's because they are LED downlights and there are not any removal lamps. 


    Those diagrams are now very outdated and it's time that the guidance is reviewed.


    I have tested the new installation with the LED downlights installed,  but not the dimmer switches having temporarily fitted plain rocker switches. 


    R2 testing with a wander lead is the  most accurate way of testing the circuit protective conductor continuity and is not affected by any installed lamps or dimmer switches. 


    Testing, R1+R2 with the lamps in is less accurate as the lamps give interconnections through them and the  neutral, but provides a polarity dead test, a high reading will indicate reverse polarity with a lamp in circuit. 


    I don't run the circuit from light to light as in the onsite guide diagrams , I go from switch to switch then take a twin and earth cable to the lights which can solve various installation and testing issues.


    Andy. 

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