Lawrence Berkeley National Laboratory

Direct Heating Equipment (DHE) is a type of space heating appliance that supplies warm air directly to the space where it is installed. It has been estimated that DHE is the primary and/or secondary source of space heating in 16% of households in California and that one-third of this fleet was installed more than 20 years ago. In addition, DHE is rarely maintained and is repaired only in extreme situations. Old DHE that is still in use has energy and emission implications. We evaluated 12 DHE units in the combustion laboratory at Lawrence Berkeley National Laboratory. Of those, eight were low-efficiency units removed from homes in California, and four were new, high-efficiency units. We found that, in most cases, the amount of natural gas used by a unit is consistent with the input rate of the model. We also found that, except for two high-efficiency models with ultra-low NOx burners, the NOx emissions from both the low- and high-efficiency models were very similar. Emissions of CO and CH4 are relatively uniform across models, except for two high-efficiency models that exhibit higher emissions of these gases. Additionally, many piloted units produced non-negligible amounts of CO and CH4 during stand-by periods, when only the pilot was lit. In general, our results are consistent with results from another study with similar scope.