Now that you’re probably conversant with vacuum performance terms and what they mean; let's take a look at the heart of your central vacuum system producing all this power!

Inside your central vacuum system is a high-performance motor running at speeds of 20,000 - 35,000 RPM's to attain very high performance.

Not all motors are created equal, however, so beware.

The anatomy of a central vacuum comprises various parts you may hear referred to in a sales presentation. These include:

• Motor Carbon Brushes
• The Armature
• The Field
• The Fans

All these, when stacked together, create what is known as "Stages." A one-stage motor, for instance, would have one fan, a two-stage motor would have two fans, a three-stage motor would have three fans.

There are also three types of motors to select, flow-thru, peripheral bypass, and tangential bypass. Which motor is used depends on what the manufacturer is trying to accomplish.

The Flow-Thru Motor

Inexpensive, these motors are normally used in conventional canister vacuums or upright vacuum cleaners with the larger, more powerful versions used in a central vacuum.

Apart from being less expensive, they also make a central vacuum sound quieter since there isn't a cooling fan spinning at more than 20,000 RPM speeds. This motor uses vacuumed air to calm itself by passing vacuumed air over the armature. It is crucial then that care is taken to ensure air is filtered and clean to prolong the life of this motor.

Often you will see this form of a motor in less expensive systems, or you may find them used in a dual-motor situation where two less-powered motors are used to create a more robust system. We will focus on that later.

The Peripheral By-Pass Motor

Again, typically less expensive than a tangential type motor, these motors employ a cooling fan on top of the motor, which blows fresh, clean air over the armature and exhaust it superficially through vents on the side of the motor.

Generally, more powerful then their Flow-thru cousins, these motors should be more dependable since clean, fresh air is being used to cool the armature. Care should be regarded in the exhaust of this unit, which is dirty and heated.

The Tangential By-Pass Motor

This is the most commonly used motor in the central vacuum business. While more expensive than it's cousins, the implementation of a tangential exhaust ensures all heated and dirty exhaust is removed from the motor chamber and expelled thus maximizing durability

Available sizes are typically 5.7" Diameter and 7.2" Diameter; the latter usually producing more power at the same or lower RPM.

Dual Motor Systems

There are many reasons why a manufacturer might choose to use a dual-motor system, the most obvious of course to increase power or "perceived" power, "if one is good two must be better."

Generally, the manufacturer is trying to boost either Suction or Airflow and, in turn, show the customer a higher Airwatts rating, which we identify as a false gauge of central vacuum power (unless measured at the end of the hose which no one does).

In many situations, one single Tangential motor is as powerful or slightly less compelling than a dual-motor system with the exception, dual-motor systems using two high-performance motors requiring a 220 Volt circuit.

Even then, suction is not much higher than one high suction single motor system.

The theory of one is good two is better does have some value provided the manufacturer is increasing the suction value.

By increasing suction, you, in turn, increase airflow velocity, which then gives you better end of hose airwatts because airflow velocity is maintained due to better suction pull power.

If your house is large, the best technique would be installing two robust single motor systems running independently of each other if probable.

What you might also consider is (if you plan on living in your home for a long time), the replacement scenario. Motors do eventually wear out and require replacement (typically after 700 - 1,200 hours). If all of a sudden one motor fails, do you replace the dead one at full retail or two at full retail plus installation, or do you wait and gamble the second motor will last for a few more years rather than a couple more months? Food for thought.

References and Resources

• How Vacuums Work