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 34 replies
  • Subscribers 32 subscribers
  • Views 12706 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

Wall Cavity Wiring.

Zoomup
Good morning on this bright and sunny start,


                          Q. Which regulation(s) specifically prohibit(s) the installation of cables in brick and block cavity walls within the cavity?


in a, Older premises?


    b, Newer premises?


If regulations exist, what reasons are provided for the prohibition? Or are we just concerned about chemical damage of cable insulation if the cables are in contact with some types thermal insulation?


Z.
Parents
  • 0
    A so called 'damp meter' will only tell you when a wall is conductive That is the rate of ions reaching each electrode, which is a product of the number of conductive ions in a unit of the material and the mobility, which is a measure of the moisture content. Pure water is a pretty good insulator, (megohms across a unit cube 1cm test cell), it is the fraction of conductive material dissolved in it that makes it conducting.


    So a high conductivity reading may be a symptom wall with a coating high in conductive salts, like lime plaster or certain types of whitewash and a low % moisture, or it may be a modern gypsum plaster , and a lot of moisture - the electric test cannot tell.  (cured gypsum plaster is almost insoluble - it crumbles but does not dissolve, in the way that say salt or sugar dissolve )

    Hence the professional use of a drill to get a core sample, and the carbide pressure cell test - calcium carbide (a white powder) gives off acetylene gas when combined with water, and will wick water out of brick dust to do so, so for a known weight of dust, the pressure rise in a closed test tank after mixing the core sample power and the carbide and closing the screw cap,  is an accurate proxy for  total water content of the sample, and so a more reliable method than the 2 prong meter
Reply
  • 0
    A so called 'damp meter' will only tell you when a wall is conductive That is the rate of ions reaching each electrode, which is a product of the number of conductive ions in a unit of the material and the mobility, which is a measure of the moisture content. Pure water is a pretty good insulator, (megohms across a unit cube 1cm test cell), it is the fraction of conductive material dissolved in it that makes it conducting.


    So a high conductivity reading may be a symptom wall with a coating high in conductive salts, like lime plaster or certain types of whitewash and a low % moisture, or it may be a modern gypsum plaster , and a lot of moisture - the electric test cannot tell.  (cured gypsum plaster is almost insoluble - it crumbles but does not dissolve, in the way that say salt or sugar dissolve )

    Hence the professional use of a drill to get a core sample, and the carbide pressure cell test - calcium carbide (a white powder) gives off acetylene gas when combined with water, and will wick water out of brick dust to do so, so for a known weight of dust, the pressure rise in a closed test tank after mixing the core sample power and the carbide and closing the screw cap,  is an accurate proxy for  total water content of the sample, and so a more reliable method than the 2 prong meter
Children
No Data

Community Rules & Guidelines