TAB Journal Spring 2015 - (Page 16)

VARIABLE VOLUME GREASE HOODS Kane Lassiter, TBE Engineered Air Balance Co., Inc. A recent project involved several variable volume grease hoods and fan systems. There were four systems, each one consisting of one exhaust fan with a VFD and two or three grease hoods, each with integral modulating damper and flow sensor. Each hood also had a temperature sensor in the duct and infrared sensors in the hood. The system concept is to vary the exhaust air flow as required by the activities in the hood, thereby reducing the energy required to exhaust and the energy required for outside air make up. The separate BAS system varies the outside air delivered to the space based on the total kitchen exhaust. This required an interface between the BAS and the hood systems which was done through Bacnet. For this system there were three touchscreen display consoles where hood variables such as damper position and airflow could be viewed. There was no proprietary software on hand to interface with the hood system controls. The system operates as follows. If the infrared hood sensor detects heat at the cooking surface, the exhaust fan is energized and the hood damper and fan flow control is enabled. The system enters what it refers to as idle mode. In idle mode the system operates at 60% of the design capacity. Upon increased cooking activities sensed by the infrared sensor and the duct mounted temperature sensor, the air volume is increased using the modulating damper 16 to maintain the duct temperature in a predetermined range. The fan VFD modulates the fan speed to maintain one of the hood control dampers near 100% open. Balance of the hoods is simple when using the manufacturer's method for determining air flow. The hood has a pressure measuring tip in the panel next to the grease filters where measurements of the exhaust plenum pressure can be taken. The TAB Journal Spring 2015

Table of Contents for the Digital Edition of TAB Journal Spring 2015

TAB Journal Spring 2015