A heat supply system with a first temperature detection unit that detects a first temperature of hot water in a tank, and a second temperature detection unit that detects a second temperature above the first temperature detection unit. When the first temperature is a first lower limit temperature or less, where a temperature increase operation by a combined heat and power supply device is permitted, a control device operates the combined heat and power supply device and flow state adjustment devices such that a heat medium circulates between the combined heat, power supply device, and hot water storage device. When the second temperature is a second lower limit temperature or less, where a temperature increase operation by a boiler device is permitted, the control device operates the boiler device and the flow state adjustment devices such that the heat medium circulates between the boiler device and hot water storage device.

Methods and systems are provided for remotely controlling a plurality of heating devices in one or more sites having a fossil fuel-based heating device and an electrical heating device. An example method involves operating a management processor to determine whether a current system supply is greater than a current system demand. In response to determining that the current system supply is greater than the current system demand, the management processor identifies at least one site to receive an opportunity to use electrical heating and transmits an opportunity signal to the local controller of the at least one site. The method can also involve operating each local controller to receive the opportunity signal from the management processor and generate one or more signals to control an operation the fossil fuel-based heating device or the electrical heating device of the site based in part on the opportunity signal.

A method of operating an HVAC system using a controller includes predicting a first predicted temperature of an enclosed space during an unoccupied time with the HVAC system off. The controller determines if the first predicted temperature is less than a set-point temperature. Responsive to a determination that the first predicted temperature is less than the set-point temperature, the controller predicts a second predicted temperature of the enclosed space if the HVAC system is operated for a first runtime. The controller determines if the second predicted temperature is less than the set-point temperature and, responsive to a determination that the second predicted temperature is not less than the set-point temperature, the controller operates the HVAC system for the first runtime.

Systems and methods are directed to water heater systems, including combi boilers and instantaneous water heaters, for initiating pre-heat and energy savings operations. Embodiments of the present invention can include at least one heat exchanger configured to heat water; and a control system in communication with the at least one heat exchanger. The control system can be configured to at least determine an expected flow demand for hot water; sense water temperature at one or more locations, including at a domestic hot water outlet; determine an end to the expected flow demand for hot water; upon receiving an indication to end the flow of hot water, initiate a recovery demand determination; and initiate a pre-heat operation based on the recovery demand determination.

An illustrative example embodiment of a method of operating a furnace configured for heating a space to be occupied by at least one individual includes determining a rate of change of a flue gas temperature of a flue gas vented from the furnace, determining a difference between the determined rate of change and a predetermined acceptable rate for a current furnace operating condition, and adjusting at least one operation characteristic of the furnace based on the determined difference satisfying at least one predetermined criterion. In some situations, such as a heating cycle, the flue gas temperature is compared to maximum and minimum thresholds.

A method for controlling a gas furnace that performs a heating operation by receiving a first heating signal; calculating a certain heating capacity smaller than a maximum heating capacity of the gas furnace, according to the first heating signal; and operating a heating of the gas furnace with the calculated certain heating capacity. The calculating of the certain heating capacity includes calculating the certain heating capacity according to a difference between an intake air temperature sucked into the gas furnace and a reference temperature.

According to various aspects, exemplary embodiments are disclosed of blow through direct fired heaters including evaporator coils and/or energy recovery ventilation.

The disclosed technology relates to a solar water heating system including a tank configured to store heat transfer fluid, a solar collector in fluid communication with the tank, and a pump system in fluid communication with the tank and the solar collector. The pump system can include a first pump, a second pump, and a valve assembly. The valve assembly can direct the heat transfer fluid from an outlet of the first pump to the solar collector when the first pump is operating and can direct the heat transfer fluid from an outlet of the second pump to the solar collector when the second pump is operating. The first pump and the second pump can transfer the heat transfer fluid from the solar collector back to the tank when the first pump and the second pump are not operating.

A system for regulating a thermo-hydraulic circuit has a thermal machine, a heat exchange terminal, a carrier fluid circulation system having a delivery duct, a return duct, and a three-way valve. The system has a pump, a first temperature sensor measuring post-valve delivery temperature of the carrier fluid downstream of the three-way valve, a second temperature sensor measuring pre-valve delivery temperature of the carrier fluid, and a third temperature sensor measuring temperature of the carrier fluid downstream of the heat exchange terminal. A flow or flow rate sensor measures a mass or volumetric flow rate of the carrier fluid. An electronic control unit has a storage device in which a model function of the thermo-hydraulic circuit is stored. A processing unit calculates values of a valve control signal and a pump control signal as function of a mass or volumetric flow rate error and a carrier fluid delivery temperature error.

Embodiments of the present disclosure are directed to a furnace that includes a blower configured to operate to force a fluid through the furnace, a motor having a rated speed, in which the motor is coupled to and configured to actuate the blower, and a controller configured to receive data indicative of an operating characteristic of the furnace and regulate operation of the motor to be at or below an operational speed limit. The controller is configured to set the operational speed limit based on the data indicative of the operating characteristic of the furnace, such that the operational speed limit is less than or equal to the rated speed of the motor.