MD Central Vacuum
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Since 1961

MD Central Vacuum Motor Education

How They Work and What They Do

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. They create low pressure inside the vacuum unit which allows air outside it, which is at 400 inches of water pressure, to rush inward in a controlled flow. This is the vacuum effect we're all thankful for when it comes to cleaning our homes. Some central vacuum motors are good for extreme suction, while others are good for being able to move air across long distances, such as a 20,000 square foot building. Depending on your need, there is an MD Central Vacuum Model for your home.

Motor Anatomy

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

In a vacuum motor, the rotating fans force outside air in through a round 1-1/4 inch opening on the bottom of the shell (you cannot see the opening in this photo). The pictured motor has two fan stages. Without opening a motor you can determine the number of fan stages by the number of seams separating metal plates on the motor shell. 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.

Measuring Vacuum Suction

Vacuum "pressure", or waterlift, 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 many inches the water is taken up. The other measurement is CFM or cubic feet per minute of air which 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. Read more about CFM vs Waterlift vs Air Watts.