Warm air space heaters, the heating system choice for large factories, warehouses and leisure centres etc need to comply with the Building Regulations Part L which currently requires a minimum of 91% efficiency for these units. In most cases this efficiency is delivered with non-condensing units. However this is set to change under future editions of the Building Regulations, with a requirement for higher efficiencies. Although the efficiency levels have not been set, 101% net efficiency is already required for inclusion in the Energy Technology List to qualify for Enhanced Capital Allowances.
Condensing for all warm air space heaters is welcomed because it has been estimated that about 18% of the world’s CO2 emissions arise from non-condensing boilers and heaters. Condensing warm air space heaters can be operated on natural gas or liquefied propane gas (LPG) and are equipped with a secondary internal heat exchanger which extracts residual heat from the flue gases. This residual heat is transferred into the warm air stream for heating space, increasing the unit’s heat output without the use of additional fuel. As this residual heat is recovered the temperature of the flue gases is reduced and this results in condensation. The volumes involved are quite low with typical condensate production rates of 0.06 litres/kWh for natural gas and 0.03 litres/kWh for LPG.
With new installations a condensate removal system can incorporated at design stage and will have a very small impact on installation costs. Where non-condensing units are being replaced with condensing systems, provision of pipework to carry away condensate away may be complex and cost more. However the cost benefits still outweigh the capital and installation costs.