Abstract: A low NOx burner assembly of a fuel-fired heating appliance is supplied with an air/fuel mixture having a substantially less than stoichiometric air-to-fuel ratio. The air-rich mixture is partially combusted to create primary combustion products disposed within an open inlet portion of a combustor structure having a catalytic converter operatively positioned within an open outlet portion thereof spaced apart from its open inlet portion. A flow of aspirating air is introduced into the combustor structure between the inlet and outlet portions thereof. The aspirating air mixes with the primary combustion products, cools them, and flows with them outwardly through the catalytic converter. This essentially completes the combustion of the remaining fuel within the cooled primary combustion products, and does so at a temperature not appreciably greater than the initial combustion flame temperature to thereby substantially reduce NOx emissions without the use of flame quenching techniques.

Abstract: A cover plate is operatively secured to the body of a housing structure, over an access opening therein, by a pair of button clinch joints which interlock two tab portions of the cover plate with two wall portions of the housing body positioned on opposite sides of the access opening. The button clinch joints function as hinges which permit the cover plate to be pivoted between closed and open positions to respectively block and unblock the access opening. In addition to other manufacturing and operational advantages, the use of button clinch joints as hinge structures provides for very rapid and economical joining of the housing body and cover plate, and eliminates the necessity for welding or in any manner puncturing the cover plate or housing body to effect the cover plate attachment.

Abstract: A system for refrigeration comprises: a compressor having an inlet, an oil sump, and an outlet; a condenser having an outlet, and an inlet connected to the compressor outlet; an expansion valve operable for controlling refrigerant flow in the system and having an outlet, and an inlet connected to the condenser outlet; an evaporator having an inlet connected to the expansion valve outlet and an outlet connected to the compressor inlet; and a control unit for operating the expansion valve to maintain a predetermined temperature differential between the temperature of oil in the oil sump and the saturated temperature of the refrigerant in the vicinity of the compressor inlet. The temperature differential is selected such that refrigerant in liquid phase in the compressor does not excessively dilute the compressor oil.