Posted By Jim Sweetman
Keith,
You ask a very interesting question. Whilst I have no intention of defaming the input from many learned colleagues, I must ask have you asked relevant technical (eg electrical) people about this? They may be best placed to give the info that you require.
However, having said that, I have recently been in the unfortunate situation where I was compelled to have a replacement central heating boiler fitted. Shortly after the initial phone conversation, I received another call, from a more technical person, where I was informed that I may need to carry out a major household refurbishment due the existing situation not meeting present regs.
In line with good practice, I had a meeting on site and we had a good look at the specific situation. Happily, a more straightforward solution was identified, without need to refurbish.
On the day when the boiler was fitted, I acted as the responsible client and kept pouring copious quantities of tea and coffee down the fitters. As a result of this good rapport, I had a chat with these chaps about the specifications/clearance distances etc. The main object being to identify what, if any, reasoning was behind the relevant criteria. Nothing fruitful really came out of it. However, the fitter did 'see where I was coming from' - my flue was 150mm above my conservatory roof (and had been for 15 years without any comment)and present requirement said 300mm, hence the reason for the 'refurbishment'. No problems had been experienced, and no-one had said anything, but now a new fitting had to comply with present, updated, requirements. I now get a feeling of 'Deja Vu'!
After all this, the morale of the tale is; get competent advice from a competent person and fit accordingly. After that, monitor. What may be acceptable criteria now, may not be acceptable in a year's time - we don't have 'crystal balls' as a general issue.
Regards
Jim