A co-fired generator for use in a continuous-cycle absorption heating and cooling system may provide heat to the interior of an annulus chamber from a first heat exchanger, such as a firetube heat exchanger, supplemented by heat to the exterior of the annulus chamber from a second heat exchanger containing fluid heated by an external source. Some embodiments may circulate fluid heated in a solar-heated collector through the second heat exchanger. Other embodiments may route exhaust gas from a combustion engine through the second heat exchanger. The second heat exchanger may be provided with a plurality of fins to increase the surface area available for thermal transfer between the heated fluid and the annulus chamber.

A control system for controlling a gas powered water heater includes a power system to provide electrical power, a valve control system to selectively hold a main gas valve in an open position, a valve pick system to selectively pick the main gas valve from a closed position to the open position, a safety system to prevent the valve control system from holding the main gas valve in the open position, and a controller. The controller is electrically powered by the power system and communicatively coupled to the valve control system, the valve pick system, and the safety system. The controller is configured to control operation of the main burner and the main gas valve using the valve control system, the valve pick system, and the safety system to provide water heated to substantially a set point temperature.

A control system for controlling a gas powered water heater includes a power system to provide electrical power, a valve control system to selectively hold a main gas valve in an open position, a valve pick system to selectively pick the main gas valve from a closed position to the open position, a safety system to prevent the valve control system from holding the main gas valve in the open position, and a controller. The controller is electrically powered by the power system and communicatively coupled to the valve control system, the valve pick system, and the safety system. The controller is configured to control operation of the main burner and the main gas valve using the valve control system, the valve pick system, and the safety system to provide water heated to substantially a set point temperature.

A fire tube boiler includes a perforated flame holder configured to hold a combustion reaction that produces very low oxides of nitrogen (NOx).