Central Heating Technical information

Recuperators - their function and purpose


The most basic heat recuperator is a hearth lined with igneous bricks (fireproof and heat retentive) this will prevent all of the heat escaping up the flue to the stars. It will allow 10% of the heat to radiate forward into the living space and be usable. Slightly more efficient is a plate metal liner which will heat quicker than brick and allow maybe 20% more heating power to enter the home. Both of the previous however pale into insignificance when compared to a cast iron insert. These come in 2 forms natural convection and fan powered. Natural convection involves the constructing of a chimney breast nowadays from fire-proof plasterboard and one or two vents placed high up to allow the heat to escape from the void between the attached metal flue and the interior of the plasterboard breast. The fan models are much more desirable as powered air distributes itself five times more efficiently than static convection and radiation. A good quality cast iron unit will, if placed strategically be capable of heating many square metres of dwelling but location as they say is everything. Seeking the advice of a professional is essential and after many years in the interior and approaching 4,000 installations there is not a circumstance or problem that we have not been able to overcome.


 

Open fireplace problems - smoking into the room.
Probably 95% of the nearly 4,000 properties that I have visited in 19 years of life in the interior of Andalusia have a fireplace that does not work properly. Most of them are built by an "albañil" (a Spanish bricklayer) and they are only concerned with the appearance nothing else. There is a mathematical formula to calculate the size of the hearth (cubic volume) and it must be in proportion with the diameter of the flue and the height of same. If those figures are not correct the fire will spill smoke from under the mantelpiece and will only work with a window or door open allowing an additional amount of oxygen into the burn area. This of course completely negates the idea of trying to heat an enclosed space! Even if it is working to the peak of efficiency, 85% of the heat produced will go straight to the stars. So whilst it may be romantic you will be paying a high price in fuel for little tangible result. The answer is a recuperator which is a hearth that works more efficiently capturing and maintaining heat so that it can serve it's purpose of raising the temperature in the home. An important point to remember is also that if the house is located above sea level additional meters of flue height will be necessary to guarantee the induction of sufficient oxygen to maintain the highest possible efficiency of burn process. Later we can look at what a recuperator is and how it works.