Cooking exhaust hood ventilation system and related methods

A method of controlling a commercial kitchen exhaust hood system of a type having multiple hood sections each with an exhaust output having an associated damper, each exhaust output feeding to a common downstream fan, wherein the operation of the fan pulls exhaust from each hood section, where damper position and fan speed control an exhaust flow rate through each hood section, the method comprising:

• for each hood section, monitoring at least one temperature condition of the hood section and, based upon the monitoring, establishing a target flow rate for the hood section, thereby establishing multiple target flow rates corresponding to the multiple hood sections;
• based upon a sum of the multiple target flow rates, establishing a fan speed and operating the fan at the fan speed;
• for each hood section, monitoring an actual flow rate through the hood section and responsively and automatically controlling damper position of the hood section to achieve the target flow rate established for the hood section, wherein the step of monitoring actual flow rate through each hood section involves evaluating an output signal of a pressure transducer of each hood section;
• and
• after the target flow rate for each hood section has been achieved, repeatedly decreasing fan speed and, for each hood section, responsively and automatically adjusting damper position in the hood section to maintain the established target flow rate for the hood section, until the damper position for at least one hood section achieves a predetermined open position, in order to reduce fan energy required to maintain the target flow rates, as follows:
• (i) determining whether the damper position of any hood section is in the predetermined open position;
• (ii) if a result of the determination of step (i) is no, decreasing fan speed by an incremental amount and, for each hood section, responsively and automatically adjusting damper position in the hood section to maintain the established target flow rate for the hood section;
• and
• (iii) repeating steps (i) and (ii) until a result of the determination of step (i) is yes, at which point fan speed is thereafter maintained.

A method of controlling the operation of a commercial kitchen exhaust hood system of a type having multiple hood sections each with an exhaust output having an associated damper, each exhaust output feeding to a common downstream fan, wherein the operation of the fan pulls exhaust from each hood section, where damper position and fan speed control an exhaust flow rate through each hood section, the method comprising:

• (a) monitoring multiple temperature sensors of each hood section and determining a proposed percent fan for each temperature sensor, where each temperature sensor has an assigned rated fan triggering temperature field define by an upper temperature and a lower temperature and, for each temperature sensor, the proposed percent fan is determined as a ratio of (i) actual temperature less the lower temperature over (ii) the upper temperature less the lower temperature;
• (b) for each hood section, identifying a highest proposed percent fan from among the thermal load conditions of the hood section;
• (c) for each hood section, based upon the highest proposed percent fan, determining a target flow rate for the hood section;
• (d) summing the target flow rates to define a target system flow rate;
• and
• (e) based upon the target system flow rate, defining an operating speed for the fan.

A method of controlling the operation of a commercial kitchen exhaust hood system of a type having multiple hood sections each with an exhaust output having an associated damper, each exhaust output feeding to a common downstream fan, wherein the operation of the fan pulls exhaust from each hood section, where damper position and fan speed control an exhaust flow rate through each hood section, the method comprising:

• establishing a target flow rate for each hood section, wherein a sum of all of the target flow rates defines a target overall hood system flow rate;
• controlling the fan speed and the damper position of each hood section to achieve the target flow rate of each hood section;
• identifying a full flow demand call from a specific hood section from among the multiple hood sections, the full flow demand call defining a full flow target rate for the specific hood section, and responsively:
• (i) determining a differential flow target rate as the difference between the full flow target rate of the specific hood section and the full flow target rate of the specific hood section;
• (ii) increasing the fan speed by a percentage amount that is proportional to A×B, where:
• A is the differential flow target rate divided by the full flow target rate,
• B is the target flow rate of the specific hood section divided by the target overall hood system flow rate,
• (iii) subsequently adjusting damper position of each hood section to achieve the full flow target rate in the specific hood section and the full flow target rate of each other hood section;
• wherein the full flow demand call is triggered by one of (i) a manual override of the specific hood section or (ii) an automatically detected excess temperature condition of the specific hood section or (iii) an automatically detected excessive rate of temperature change condition or (iv) an automatically detected excessive VOC condition.