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and the boiler pumps should be on the return to the boilers, not on the boiler flow, as shown in the diagram. To my mind the rules are correct and the diagram wrong. Rodney Perry (Fellow)
This month: More ‘burning issues’ on biomass, rare chimney manual found on Amazon and teachers on the receiving end
Biomass grilled Judging from the article in the December issue of the CIBSE Journal and further reading, the view is that biomass is an unsustainable, limiting and regressive short cut to reducing emissions. To consider the use of a biomass system is fraught with many pitfalls and some not inconsiderable risks to health and safety, ongoing effective planned preventative maintenance, correct system operation and the safe storage of fuel pellets. Let’s also not overlook the fact that
the burning of wood in any form is a pollutant. Even under complete combustion, wood burning emits about the same CO2
and NO2 as oil; when
incomplete it is a fairly unpleasant mix. Clients will start with all good intentions but, ultimately, will fail to ensure efficient control over time. It is a falsehood by the market/ industry to claim biomass systems as a ‘green’ alternative. It takes 20 years for a conifer to reach maturity, soaking up CO2
, and a matter of hours to release
it all back into the atmosphere. How is that sustainability? The emphasis must be on driving up the thermal performance of buildings, appropriate use of renewable technology and improved efficiencies from the plant that we specify and design systems around. As an aside, the author implies that skills to size a flue are lost. Just to let
16 CIBSE Journal January 2013
him know, some of us older gits with ‘the knowledge’ are still doing it the long-hand way. David Elloway, Bovey Tracey
Rare chimney find On page 24 of the article, ‘Burning issues’ (CIBSE Journal, December 2012), the author says: ‘very few people working now have ever sized chimneys.’ Who then is designing the present generation of chimneys, I wonder? Admittedly, the procedure can be
lengthy and involve calculation of gas flow rates, buoyancy, pressure drop and exit velocity, which is probably why engineers have preferred to leave it to the remaining experts. Some readers may remember the Brightside Chimney Design Manual, last published in 1979 by Technitrade Journals and now out of print. It presented a relatively easy solution through a series of nomograms, which took account of all the relevant variables. A few ‘rare’ copies still exist – one listed by Amazon is priced at $500. A A Field FCIBSE
Breaking the rules I enjoyed your article ‘Burning Issues’ in the December Journal – especially the item ‘common header design rules’ on page 24. It was a pity that the diagram above
the rules broke rule 4 – that the header should be the neutral point
So, what are our members doing about the education cliff-edge that, in my view, is fast approaching?
Editor: Thank you for the observation. The intent of the diagram was to illustrate an ‘as-installed’ arrangement that had operational, metering and commissioning issues. The paragraphs identifying these issues were deleted, as the diagram should have been. An article on header design will appear in the new year.
Not every thing about biomass I read with interest your biomass article in the December issue of the Journal. Despite the front page title, stating
‘Biomass: the facts, everything you need to know about design and specification’, I was disappointed to see that no mention was made about whether biomass sources to heat buildings is appropriate, and if so, when this may be. Nor was there any mention of the ethical issues of biomass sourcing, or of the carbon intensity of the burning of biomass and recent research, which points to biomass leading to a ‘carbon debt’. Sofie Pelsmakers, Doctoral researcher DipArch MScArch MRes ARB RIBA UCL Energy Institute
Engineering intake going off a cliff
Why we must plug the engineering gap I welcomed the Engineering Knowledge supplement with last month’s CIBSE Journal; it shows that the institution is looking to the future and recognises the potential problems ahead, where the grey-haired baby-boomers, like myself, will have no active part. However, I still do not believe that
CIBSE really realises the danger, in years to come, of too few building services engineers struggling to service the construction boom after the present recession disappears over the horizon. How many of our members read The Sunday Times on 18 November,
www.cibsejournal.com
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