Of course, on Earth, there is no such thing as a true vacuum. So what does a "central vacuum" actually do? Central vacuums pull with intense force by utilizing turbine energy. Central vacuum motors are powerful devices that spin a turbine and move air. Some central vacuum motors are good for extreme suction. Other motors are good for being able to move air across long distances, such as a 20,000 sq/ft building. Depending on your need, there is an MD motor combination for you.

MD central vacuum motors are usually located in the base of our units, which is the most efficent placement of a central vacuum motor.

In a vacuum motor, the rotating fans force outside air in through an opening on the bottom of the shell (you cannot see the opening in this photo). The pictured motor has two fan stages - their is one seam separating two metal plates on the shell of the motor. The diameter of this motor is referred to as 5.7", or the width of the shell.

The components above the rotating fans perform the function of getting electricity to spin the armature which then spins the fans.

The exhaust on this motor is peripheral - it comes out the holes above the shell. Other motors have tangential or what looks like a horned exhaust.

Vacuum "pressure" is measured without any air flowing through it. A completely sealed vacuum measures the power or force of the pull and is usually done by lifting water up a column and measuring how far inches the water is taken up.. This is called waterlift. The other measurement is CFM or cubic feet per minute of air and this measures how much air the vacuum moves without resistance - the opposite of a sealed vacuum. These are the two key measurements and both must be present in a good relation to have a satisfactory vacuum. Central vacuum motors are usually larger then portable ones and offer greater vacuum power. The AirWatts measurement is a formula using waterlift and CFM.

Question: How do you test and troubleshoot the motors, transformer, and relay?

Answer: We strongly recommend that a professional vacuum specialist follow these directions to trouble shoot components. You can locate a local dealer, mail your unit to MD, or visit a vacuum repair center.

Continue to the Motor Troubleshooting guide→