Greetings. This is my first post here. My area of professional concern is EMI from power frequency magnetic fields generated by certain wiring errors found frequently in the U.S.A.
I read with interest the excellent threads (from 2001)on the Ring mains circuits used in the UK. I understand and would have predicted the disadvantages listed. I also understand how they came into being in the '40s.
I noted that it was mentioned that a stronger magnetic field would be generated by the unequal phase and neutral currents which would be created when there was a break in one of the conductors. This was given little weight, though in the USA such fields do interfere with computer monitors and other sensitive electronic instruments.
A reasonable assessment of the health concern is not available to most electricians since the controversy has caused the media to under-report the ongoing research. Opinions are generally formed due to attitude rather than knowledge of the research.
There was one assessment of risk which is worth knowing about: in 2001 the International Agency for Cancer Research (IARC), an agency of WHO (World Health Organization) reviewed the recent mega-studies of the many epidemiological studies conducted over the years, and by combining them came up with a solid connection between childhood leukemia and magnetic field exposure of 0.4 microTesla (4 milligauss - mG). Thus this conservative body designated this level as a possible carcinogen.
In the USA our Code almost completely excludes "net current" circuits and their magnetic fields, so here is a difference, since the UK Ring circuits would not be allowed, since the conductors are paralleled (NEC 310-4).
So now I will see if there is any interest in this post.
Karl Riley
