Safe design of R290 ducted air-conditioning equipment.

Currently R290 is used in certain types of air conditioning equipment, such as mini-splits, portables, window units and chillers. Application in ducted air conditioning has hitherto been limited to one-off trials. This study describes the interim findings of a project implemented by UNDP and funded by the MLF of the Montreal Protocol, to develop a range of small capacity ducted packaged (“rooftop”) and ducted single split air conditioners. The main areas of investigation include system design and optimisation (whilst minimising refrigerant charge), determination of leak amounts and options for leak control and characterisation of refrigerant concentration behaviour arising from a leak. Unlike the afore-mentioned types of air conditioning equipment, ducted equipment possess certain features that infer potential technical challenges where it concerns applying R290 safely. These are primarily the distribution of leaked refrigerant through ducting and from non-ducted air return configurations whilst the indoor unit is positioned within closets. Findings and developed measures are described.