Using the drain wire in FP200 plus as a signal conductor... can I?

Also begs the question of why FP 200 type cable was selected in the first place?  If it was for its fire resistance then what happens to your signal if the foil shorts out to earth or the screen of other cables when the outer plastic sheath melts in a fire? (as I understand it, the bulk of the fire resistance is due to the core insulation and mica wrap rather than the outer sheath) If it was for its EMI screening properties then substituting a changing signal for earth on the foil isn't going to be beneficial for the other cores and your signal wire wouldn't have the benefit of any screening.


If on the other hand you're only using FP becuase it was 'free' in some sense - say you had a bit left over in the van, or re-using some that had previously been installed for something else, and otherwise a bit of bell wire would have done, then you might be fine.


   - Andy.

Also begs the question of why FP 200 type cable was selected in the first place?  If it was for its fire resistance then what happens to your signal if the foil shorts out to earth or the screen of other cables when the outer plastic sheath melts in a fire? (as I understand it, the bulk of the fire resistance is due to the core insulation and mica wrap rather than the outer sheath) If it was for its EMI screening properties then substituting a changing signal for earth on the foil isn't going to be beneficial for the other cores and your signal wire wouldn't have the benefit of any screening.


If on the other hand you're only using FP becuase it was 'free' in some sense - say you had a bit left over in the van, or re-using some that had previously been installed for something else, and otherwise a bit of bell wire would have done, then you might be fine.


   - Andy.