Car Wash Vacuum Variable Speed Drive

Measure energy saved when a VSD is added to a car vacuum cleaning system at a full service car wash. VSD control allows the vacuum motor to change speed to match needed vacuum pressure and air volume.

This field evaluation accesses the viability of the variable speed drive (VSD) technology and measures the potential and incremental energy savings and demand reduction when compared to conventional type constant speed vacuum pump motors in the car wash industry. This field evaluation further demonstrates the difference in the operation of a VSD compared to the baseline/constant speed vacuum pump motor. The vacuum system is a significant component of a car wash and is used to vacuum the interior of a car when a customer purchases a car wash service. Typically, these vacuum pumps operate by a conventional constant speed motor that is turned “ON” when a facility opens for business and runs constantly at full-speed until the end of each business day. As a result, a car wash uses the same amount of energy regardless of the number of cars actually serviced. VSDs can be retrofitted on an existing vacuum pump and piping system to realize energy savings when the system is idle or running at a very low load. VSD is a system that controls the amount of rotations per minute (RPM) of a motor by modulating load-side power frequency in response to the pressure feedback signal provided by the feedback loop transducer. This helps in maintaining a constant vacuum pressure in the main duct to which the hose drops are connected. The VSD evaluated in this project is a three-phase drive connected to a conventional motor that supplies vacuum pressure to the hose drops where cars are vacuumed. Test sites were selected in order to include various size car washes (small, medium and large) and to analyze the impact and savings potential of a VSD. Site 1 had two vacuum pump motors each rated at 20HP (total 40HP); site 2 had one 20HP vacuum pump motor and; site 3 had one 10 HP vacuum pump motor. Measurements taken in the field verify the energy savings and demand reduction of a VSD compared to the baseline. Additionally, spot measurements for change in vacuum pressure were recorded with the corresponding change in motor speed. Pressure changes were recorded in order to observe the affect of VSDs on the mechanical performance of a vacuum pump motor.