In the last week I’ve been made aware of two problems with different biomass installations, both of which are due to the use of inappropriate technology for the situation…Last week I was called by a consultant who is involved in a biomass installation project where one of the potential suppliers is recommending the client install a boiler far larger than the heat demand of the project, simply to increase the support the project will get under the Renewable Heat Incentive (RHI).
This potential problem was flagged up by a recent piece in Private Eye, which drew a response from Gaynor Hartnell of the REA, who pointed out the potential issue during the design phase of the RHI. In her letter, Gaynor said, ‘Exploiting this perverse incentive is likely to cost any customer dear. Over-sized boilers don’t operate efficiently and can cause serious operational problems. The costs of which are likely to outweigh any extra subsidy earnings.
‘It’s not ideal, and we will do our best to educate customers and warn unscrupulous operators that oversizing boilers is bad practice.’
Unfortunately, it appears that many of the cowboy firms which have been plaguing the PV market for the last couple of years are now jumping into the biomass sector, driven by the fall in FIT rates, the attractiveness of the RHI and amble availability of a wide range of biomass boilers.
If anyone has any information or examples of deliberate over-specifying of boilers, please contact us in confidence.
The 21kW biomass pellet boiler installed in the 20 bedroom hotel.
The second incident was brought to my attention at the weekend and is the complete opposite. Someone visiting a Scottish hotel was surprised to hear that their biomass boiler was very unreliable and consuming bagged pellets at the rate of 1 or 2 bags a day!
I was sent a picture, which turned out to be a 23.7 Lucrezia pellet stove which features a 21kW back boiler, designed for household use. Whichever idiot recommended that this was a suitable unit for a 20 bedroom hotel / hostel in the north of Scotland wants shooting!
From what I can discover, as maximum output this unit will consume about 5kg of pellets an hour to produce ~21kWth. It’s no wonder its eating pellets. As a comparison, one 20 bedroom hostel in Wales has a 150kW biomass boiler. This one is Scotland is effectively just 1/7th of the size it needs to be!
I’ll be passing the details on to a contact who may be able to advise on the the size of boiler required, but I have been warned that, “fixing it is quite low on the list due to cost.”
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16 May 2012
Hi Richard two thoughts a wanted to share:
re hotel, I think I know the project and if its the one I think then the client detemined the boiler rating and connectoin. 2 x bags of pellets per day is about right for a 25kW nominal boiler its doing what its abel to do. ofcourse that you have to carry 2 bags every day through the house is the key flaw to the stove-boiler product. although most seem to suffer from being too fragile to last a Uk winter or two.
the key thought is that the client wont buy from you if you tell him he is wrong.
on the bigger boiler, as we have discussed on other forums: the succesful biomass installtion relies on many aspects being correct. key are: boiler to match avaiable fuel, fuel store being correctly sized adn positined to accept economic deliveries. fuel store being adequate to handle the fuel and deliver to the boiler, buffer sized so that boiler does not cycle excessively. boiler and buffer and heating controls integrated so that cycling does not occur dueto hihg return temperature. flue correctly sized adn installed to remove combustion products safely and not produce incorrect draft on the boiler. boiler positioned to allow proper maintenance in commercial jobs, heating controls (BMS) correctly programmed to meet design requirements. heat users educated onwhat to expect form heating. boier opeator educated on how to service and maintain boiler. if any one of these is not optimal then the system will not work and the boier (usually) is blamed.
what has this to do with oversized boiler? a correctly instllalled boiler with correctly sized buffer and controls doesnt mind being over sized it just runs less and has cost more to put in.
as a real boier installer with a tied product range I select teh boeir with the best fit to the cleints needs from what I have available. which means a 100kW boiler for a 65kW nominal load. in rhi terms this may give the client more income opportunity if they use more heat. it may cost more than competitors products ( different size or otherwise) but clients buy form me becasue i do it right and support the install never because i am cheapest becasue i never will be. OTOH i suspect my still working and in use after 3 years percentage is a lot higher than the national average alas I have lost contact with some old customers .With the RHI there are also lots of undersized boilers going in at the 200kW cut off. so swings and roundabouts.