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
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