Central Vacuum Terminology
(Continued)
Now that you are familiar with
performance terms and what they mean, lets take a look at the heart of your
central vacuum system producing all this power!
Inside your central vacuum is a high
performance motor running at speeds of 20,000 - 35,000 RPM's to achieve very
high performance.
Not all motors are created equal
however so buyer beware.
Ametek/Lamb is renown for producing
high quality
motors and has been the backbone of the central vacuum industry for decades.
As of late, other motor manufacturers
have come on the scene offering motors for central vacuum systems among which
include Domel and Electro-Motor.
The anatomy of a central vacuum
consists of several parts which you may hear referred to in a sales
presentation. These include (1) Motor Carbon Brushes (2) The Armature
(3) The
Field and (4) The Fans, which when stacked together create what is referred to
as "Stages". A one stage motor for example 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 choose, flow-thru, peripheral by-pass, and tangential bypass. Which motor is
used depends on what the manufacturer is trying to achieve.
The Flow-Thru Motor
Inexpensive, these motors are
generally used in conventional canister vacuums or upright vacuum cleaners with
the larger more powerful versions used in a central vacuum.
Aside from being less expensive they also make a
central vacuum sound quieter since there isn't a cooling fan spinning at speeds
in excess of 20,000 RPM. This motor uses vacuumed air to cool itself by passing
vacuumed air over the armature. It is critical then that care be taken to insure
air is filtered and clean to prolong the life of this motor.
Often you will see this type of motor in less
expensive systems or you may find them used in a dual motor situation whereby
two lesser powered motors are used together to create a more power
system. We will talk about that later.
The Peripheral By-Pass Motor
Again typically less expensive then a tangential
type motor, these motors actually employ a cooling fan on top of the motor which
blows fresh clean air over the armature and exhausts it peripherally through
vents on the side of the motor.
Generally more powerful then
their Flow-thru cousins these motors should be more reliable since clean fresh
air is being use to cool the armature. Care should be considered in the exhaust
of this unit which is dirty and heated.
The Tangential By-Pass Motor
This style is the most commonly used motor in the
central vacuum industry. While more expensive then 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 longevity
Available sizes are usually 5.7" Diameter and 7.2" Diameter; the latter generally producing more power at the same
or lower RPM.
Dual Motor Systems:
There are a number of reasons
why a manufacturer might opt 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 to the consumer a higher Airwatts rating which
we know to be a false gauge of central vacuum power (unless measured at
the end of the hose which no one does).
In many cases one single
Tangential motor is as powerful or slightly less powerful then a dual
motor system (click on graph below) with the exception, dual motor
systems using two high performance motors requiring a 220 Volt
circuit. Even then suction is typically not much higher then one high
suction single motor system.
The theory of one is good two
is better does have some merit 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 greater suction pull power.
Rather then install a dual
motor system if your house is that large, the best method would be to
install two powerful single motor systems running independent of each
other if possible.
What you might also take into
consideration is (if you plan on living in your home for a long period of
time), the replacement scenario. The fact is, motors do eventually wear out
and need replacing (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 just wait and
gamble the second motor will last for a few more years instead of a couple
more months? Food for thought.
There are
two ways to increase performance in a dual motor system:
Air Series:
One vacuum motor feeding it's heated dirty discharge air into the intake of the
second motor. Increases vacuum suction (inches of waterlift) by 60-70%. This
design is not recommended as higher air temperatures in the fan system could
result in bearing problems due to the elevated temperature. Not
recommend by Ametek/Lamb.
Air
Parallel:
While operating vacuum motors in air parallel, two motors draw air from a single
plenum chamber. This has the effect of nearly doubling the airflow (CFM) of the
system while the vacuum (inches of waterlift) level remains comparable to if a single motor
was used.
"When applying motors in this manner, care must be taken in the design to
accommodate the increased airflow. If restrictive tools and hoses are used in a
cleaner, the potential air flow advantages gained by the parallel arrangement
may be negated." Ametek/Lamb Product Review.
