A vent attachment facilitates attaching a coaxial air intake and exhaust vent of a tankless water heater to a Category I vent, such as B-vent. The vent attachment comprises a first end with a coaxial connector comprising a central exhaust pathway and a circumferential air intake pathway. The vent attachment also comprises a second end with a tubular exhaust vent connector in fluid communication with the central exhaust pathway. The vent attachment further comprises a frame that encloses the central exhaust pathway and comprises a mesh configured to provide fluid communication through the frame with the air intake pathway. Additionally, operation of the tankless water heater is modified to ensure that the exhaust generated is suitable for venting through a Category I vent. The tankless water heater maintains a high fuel consumption rate such that the temperature of hot water produced increases throughout each of a plurality of burner stages.

A vent attachment facilitates attaching a coaxial air intake and exhaust vent of a tankless water heater to a Category I vent, such as B-vent. The vent attachment comprises a first end with a coaxial connector comprising a central exhaust pathway and a circumferential air intake pathway. The vent attachment also comprises a second end with a tubular exhaust vent connector in fluid communication with the central exhaust pathway. The vent attachment further comprises a frame that encloses the central exhaust pathway and comprises a mesh configured to provide fluid communication through the frame with the air intake pathway. Additionally, operation of the tankless water heater is modified to ensure that the exhaust generated is suitable for venting through a Category I vent. The tankless water heater maintains a high fuel consumption rate such that the temperature of hot water produced increases throughout each of a plurality of burner stages.

A heating control system including an air circulation fan, a heating unit, a memory, and a microprocessor. The microprocessor is configured to operate the air circulation fan at a first speed and the heating unit in a first configuration to achieve a first temperature rise where less than all of the burners are active. The microprocessor is further configured to compare the first temperature rise to a first temperature rise threshold and transition the air circulation fan to a second speed to achieve a second temperature rise when the first temperature rise is less than the first temperature rise threshold. The microprocessor is further configured to compare the second temperature rise to a second temperature rise threshold and transition the air circulation fan to a third speed when the second temperature rise is greater than the second temperature rise threshold.

A controller is configured to set total stop in which operations of all of a plurality of water heaters are stopped when an abnormal condition of a fan or an abnormal condition in communication is sensed in any of the plurality of water heaters while at least one of the plurality of water heaters is operating. The controller is further configured not to set total stop when an abnormal condition of the fan or an abnormal condition in communication is sensed in at least one of the plurality of water heaters while a sensing element for sensing a backflow of an exhaust from an exhaust path assembly is connected to the controller.

A combustion device includes a combustion control section which controls combustion in the combustion device; a setting section operated to set information indicating whether or not a plurality of combustion devices are in a common vent discharge state; and a memory section which stores therein connection configurations with the other combustion control sections to which the combustion control section is communicatively connected, and the combustion control section determines whether or not the combustion control section can communicate with a linkage control section or the other combustion control sections, and inhibits combustion in the combustion device to which the combustion control section belongs, in a case where the combustion control section determines that the combustion control section cannot communicate with the linkage control section or at least one of the other combustion control sections and the common vent discharge state is set by the setting section.

A heating control device comprising input/output ports, a memory, and a microprocessor. The microprocessor is configured to transmit a first electrical signal to operate an air circulation fan at a first speed and a heating unit in a first configuration to achieve a first temperature rise where less than all of the burners are active. The microprocessor is further configured to obtain a return air temperature, obtain a room air temperature, and determine a temperature difference between the return air temperature and the room air temperature. The microprocessor is further configured to compare the temperature difference to a temperature rise threshold and transmit a second electrical signal to transition the air circulation fan from the first speed to a second speed to achieve a second temperature rise that is less than the first temperature rise when the temperature difference is greater than the temperature rise threshold.

A high turndown furnace is provided for an air handling system. In one example, the furnace is provided with a plurality of tubes divisible by four with a first modulating valve supplying gas to of the tubes and a second modulating valve supplying gas to of the tubes. In one aspect, the furnace is capable of providing a 16:1 turndown. In one aspect, the furnace is capable of providing seamless turndown operation throughout the entire firing range.

A heating control device including input/output ports, a memory operable to store smoke output thresholds, and a microprocessor. The microprocessor is configured to transmit a first electrical signal to operate an air circulation fan at a first speed and a heating unit in a first configuration to burn a lubricant at a first temperature where less than all of the burners are active. The microprocessor is further configured to obtain a smoke output measurement for the first temperature, compare the smoke output measurement to the smoke output threshold, and transmit a second electrical signal to transition the air circulation fan to a second speed to burn the lubricant at a second temperature that is greater than the first temperature when the smoke output measurement is less than the smoke output threshold and is less than the first temperature when the smoke output measurement is greater than the smoke output threshold.

A heating control method includes determining a first speed for an air circulation fan that corresponds with a temperature set point using a temperature map that maps temperatures to speeds of the air circulation fan and operating the air circulation fan at the first speed and a heating unit in a first configuration with at least one active burner from a plurality of burners where less than all of the burners are active when the heating unit is in the first configuration. The method further includes measuring a first temperature while operating the air circulation fan at the first speed, determining a temperature difference between the first temperature and the temperature set point, comparing the temperature difference to a temperature difference threshold, and updating the temperature map to map the first speed to the first temperature when the temperature difference is greater than the temperature difference threshold.

A heating control device comprising input/output ports, a memory, and a microprocessor. The microprocessor is configured to transmit a first electrical signal to operate an air circulation fan at a first speed and a heating unit in a first configuration to achieve a first temperature rise where less than all of the burners are active. The microprocessor is further configured to obtain a return air temperature, obtain a room air temperature, and determine a temperature difference between the return air temperature and the room air temperature. The microprocessor is further configured to compare the temperature difference to a temperature rise threshold and transmit a second electrical signal to transition the air circulation fan from the first speed to a second speed to achieve a second temperature rise that is less than the first temperature rise when the temperature difference is greater than the temperature rise threshold.