星空传媒

Just how wrong can you be? Mr Ferguson (鈥楽ocket to 鈥榚m', EMC, Feb, p5) seems to think that it is necessary to locate and mark the centre point of ring circuits. This is wrong. There never has been, not even in the much decried 15th Edition, a need to identify the mid-point of ring circuits. The recommended test method simply indicated that halfway around the ring the resistance between the phase and neutral conductors joined together in parallel would be half the resistance of the end-to-end value of either conductor; this means that at sockets anywhere else in the ring the value will be less than half.

Unfortunately this simple fact sent half of the industry searching for and marking the mid-points of ring circuits. I am aware that many consultants ask for the mid-point to be marked on the as-installed drawings - all a lot of nonsense. IEE Guidance Notes 3 and the On-Site Guide published in 1991 do not mention the mid-point.

Where did Mr Ferguson get the idea that I want to ban ring circuits? I have not said so, although there is evidence to suggest that change is necessary.

For many years, I delivered inspection and testing training for ECA members. When I asked if anybody had found ring circuits cross-connected with other ring or radial circuits, almost without exception, people had. There must be hundreds of faulty ring circuits in this country.

I suspect that Mr Ferguson obtained the misconception from the ECA power technical committee minutes that reported on the paper I presented last November. The minutes do not say that ring circuits should be banned. The paper suggests that there is more than one method of installing 13 A socket outlets and radial or tree circuits can be safer and more cost-effective, giving better value for money. There is therefore a spin-off for contractors. I suggest Mr Ferguson gives it a try.

Roger Lovegrove ECA power technical committee member

On the defensive

How sad that the reply to my letter in February's issue is both defensive and clearly misses the point I was trying to put across. Why did Mr Simmons (鈥楥ome an' have a go', EMC, March, p5) get the idea that I thought the ECA is solely responsible for the Wiring Regulations? Of course the ECA is a "cog in a wheel"; what the membership finds disconcerting is that the "cog" does not appear to be turning and representing the views at grass roots level. If it did, we would have seen the ECA object to both the wiring colour changes and Part P.

Mr Simmons' final emotional paragraph does little to inspire confidence in the technical committee to which he belongs. The "practical contribution", which he suggests we make, is being made when we voice our opinions to the ECA. If he and his colleagues consider these active (and helpful) opinions to be 鈥榮niping', I suggest that they listen a little more carefully.

My purpose was never to criticise the ECA per se but to promote discussion and try to regain some common sense stability within the industry. I fear that if all members of our committees are as blinkered as Mr Simmons then things ain't ever going to get better.

Andrew Ferguson Solent Power Systems Southampton