In an industrial Finishing (water heating) System, product drying ovens and paint curing ovens are used as part of the process.

Large ovens must be purged with 4 complete air changes before the burners can start. To reduce the purge times, the exhaust volumes are often increased to more than what is required during actual drying and curing periods. Heated air is often being wasted during the production times with oversized exhaust fans to accommodate reasonable purge times.



In order to reduce operating costs, two exhaust fan speeds or a motorized damper must be used to adjust the exhaust air flow for purge or production periods but wastes electricity when running the fan at high speed.

Controlling the motor speed is the best technology, but must have the proper interlocks to maintain a safe operating environment, and must be acceptable to the governing body.



ProTherm technical staff designed and installed Variable Frequency Drive (VFD) control on a number of ovens. The controls were designed to be properly interlocked and meet the requirements of the Technical Standards and Safety Authority (TSSA) of Ontario and the local gas utility.

The savings from fuel and electrical costs resulted in a payback of 13 months.