Quillan Posted April 8, 2013 Share Posted April 8, 2013 [quote user="Théière"][quote user="Quillan"]Now not having a go at anyone but it seems this 1:1 might not possibly be correct, I draw your, and anyone else's attention, to page 51 that shows on average at -10, as that was a figure mentioned, that the COP figure could be between 1.8 to 2.0 and a little lower for -12. If I have misinterpreted the numbers please don't have a go just try and explain my error in simple terms.[/quote]Q, it was more a sense of getting the concept across that with colder outside air the COP will fall dramatically from 3:1 or better. The actual COP depends on many things not least the design and it's ability to cope with colder weather. Even the best units will drop to a COP of 1:1 when it's cold enough and the heat needs increasing. The further apart those numbers are the less COP you receive. It's ok in a lab to simulate but that's not real world and in a cold limestone house you may well need to set the heat warmer than their stated 21 deg and with temperatures dropping to around -17 round our way the other year I would much rather over spec and have heat in reserve than under spec and be cold even if it is only for 2 weeks a year.[/quote]So when I looked in to this a few years ago I was very sceptical about this COP number and more importantly the claims on saving money which is my main driving force. As far as I was aware you can't get something for nothing and going back many (many) years to school physics power in equals power out and that whilst you might get to 95/98% efficient you couldn't effectively get more power (in this case heat) out of the power you put in let alone three or more times the power.It seems to me from what I have read that the 'secret' in all this is the gas and actual pump used. From what I have read, and this link I gave seems to confirm this, there are only a handful of pump manufacturers with names like Toshiba and Mitsubishi being the main movers. Now my cheaper units from BricoDepot actually have Toshiba pumps in them so it's nice to know they are not 'Oki Coki' but an actual brand. Gas, well with slight variances that seems to be much the same these days due to environmental controls.Anyway being rather sceptical I decided to buy just one and run it for a year and see how it went and I have to say I was very surprised especially as that year we had temperatures down to -17 on more than one day. The heat is relatively instant, they take about five to ten minutes to start throwing out real heat and in the living areas we have them set to 23 deg in winter. Now I have no idea how you can measure the COP rating in a normal household environment but what I do know is that either the old, very expensive, electric radiators were absolute cr*p which at 600 Euros a pop back in 1998 I doubt or these things really are as good as they say they are and to my mind the size of the reduction in my electricity bill seems to confirm that. Even in a case like yours with thick walls (I am not trying to sell them to you by the way) the potential saving would pay outright for two electronic paraffin heaters and enough paraffin to run them for two weeks and after the second year still save money, you could even install another wood burner.I read a bit of that report last night in a bit more depth and I did find it interesting that smaller is better i.e. don't buy massive outside units and try and get 5kw out inside but go for the 2.5 to 2.8kw units or bi split units (one bit outside and two bits inside) as smaller units are more efficient. The also tested cheap Chinese imports (well they actually say Asian) and found that whilst they were not as good as branded but because they used some branded components like Toshiba etc pumps there was only a small difference in performance. Also don't forget that these results are a combination of individual tests carried out by many people in many EU countries. Link to comment Share on other sites More sharing options...
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