Abstract: A single system for providing heated water at two different temperature levels for space heating purposes and for domestic water heating purposes is provided. The system can be constructed using only one burner. The system features a first loop for circulating domestic hot water at a lower temperature from an insulated tank, through a first heat exchanger where the water is heated, and back into the insulated tank. The system also features a second loop for circulating space heating water at a different temperature through a second heat exchanger, where the water is cooled, through the first heat exchanger, where the water is heated, and back to the second heat exchanger, where the water is again cooled. A single diverter valve or equivalent is used to determine which heating loop is required and will be activated.

Abstract: A vent device is provided for common venting of exhaust gases discharged from separate apparatus at different vent pressures. The vent device provides a passageway and exhaust gas inlets for combining the exhaust gases and conveying them to a single vent stack. The higher vent pressure exhaust gases are discharged within the passageway using a venturi or jet pump effect to provide a zone of reduced pressure in the passageway for inducing the flow of the lower vent pressure exhaust gases into the device.