| 摘要 |
A control circuit for a heating system having a gas burner assembly, a heat absorbing coil, a heat releasing coil, a circulating pump for pumping a hydronic fluid between the two coils, and an air blower for the heat releasing coil is disclosed. The control circuit includes a thermostat located in the space to be heated and a first relay switch which electrically connects the circulating pump in response to a signal from the thermostat. A combustion safety control is electrically connected to the thermostat, a main gas valve, and a flame sensor such that the main gas valve is open in response to a signal from the thermostat and the main gas valve is closed where no signal is received from the thermostat or an insufficient signal is received from the flame sensor. A second relay switch is electrically connected to the air blower, the circulating pump, and a hydronic fluid temperature sensor such that in response to a signal from the fluid temperature sensor the air blower and the circulating pump are electrically connected. After the thermostat ceases to send a signal to the first relay switch, the second relay switch acts to electrically connect the air blower and the circulating pump so long as the temperature of the fluid is sufficient to provide heat to the space to be heated. A number of safety features are also provided.
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