Rules and Guidelines
Want to participate in the discussions? Please read our Community Rules and Guidelines. Need some help? Visit Support and Answers.

  • State Not Answered
  • Locked Locked
  • Replies 5 replies
  • Subscribers 32 subscribers
  • Views 474 views
  • Users 0 members are here
Options
You may also be interested in
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

New Consumer Unit and Two Way and Intermediate Light Switches Problem.

Zoomup
Mornin' All,


Imagine this scenario. You have just installed a new R.C.B.O. consumer unit in a 1970s bungalow. The supply appears to be TN-S. But may be TNC-S in reality. There are two lighting circuits each supplied separately by an individual B6 30 mA R.C.B.O. The hallway is an "L" shaped design with two ceiling pendant lights. There are two two way switches at the ends of the hall way, but between them are two intermediate switches as well. Four switches in total control the two pendants together. All cables are in good condition and the insulation resistance is very high between L and N and all Lines. There is evidence of rodent infestation in the loft.


When just the front door lamp is fitted the light works and switches correctly from all four switches.



But when the second (remote) lamp is fitted as well and turned on by any switch, both R.C.B.Os trip off.


Why?


Z.




Parents
  • 0

    But when the second (remote) lamp is fitted as well and turned on by any switch, both R.C.B.Os trip off.



    My guess would be that 2nd lamp is connected to the "wrong" circuit's N. 1970s probably sheathed singles 'spider wiring' so very tempting to take a black to the nearest convenient N terminal rather than necessarily one on the same circuit which might be further away - usually seen in houses with the landing light fed from the downstairs L and upstairs N.


    Correct RCBO trips because the circuit has lost one lamp's worth of current - other RCBO trips because it's equally out of balance having mysteriously gained the same.


      - Andy,
Reply
  • 0

    But when the second (remote) lamp is fitted as well and turned on by any switch, both R.C.B.Os trip off.



    My guess would be that 2nd lamp is connected to the "wrong" circuit's N. 1970s probably sheathed singles 'spider wiring' so very tempting to take a black to the nearest convenient N terminal rather than necessarily one on the same circuit which might be further away - usually seen in houses with the landing light fed from the downstairs L and upstairs N.


    Correct RCBO trips because the circuit has lost one lamp's worth of current - other RCBO trips because it's equally out of balance having mysteriously gained the same.


      - Andy,
Children
No Data

Community Rules & Guidelines