This demonstration will illustrate the variable speed capabilities and energy efficiency of
the Greenheck Vari-Green motor. It will also compare the performance of the Vari-Green
motor to another technology -- the P S C (or permanent split capacitor) motor with a speed
controller.
Our demonstration set-up is very simple, consisting of two model G-101 fans with identical ¼
horsepower operating loads. The fan on the left is equipped with a Vari-Green motor and
a simple zero to ten volt dial for fan speed control. The fan on the right has a P S C
motor and common rheostat type speed controller. Digital output displays will indicate fan
speed in R P M and input power in Watts for each fan.
First, we'll run both fans at the top end of the P S C motor speed range, which is approximately
1,720 r p m. This operating point and corresponding motor load will show the P S C motor at its
peak efficiency.
We will look at each unit separately, starting with the Vari-Green fan. As we zoom in on
the display panel, take note that the fan speed is about 1,720 r p m and the power input
reading is about 220 watts. Now let's take a look at the fan with the P S C motor. As
we get a closer look at the display panel, we can observe that the fan speed has been
matched at about 1,720 r p m. Notice that this fan is consuming roughly 270 watts of
power.
Let's document these results and make an efficiency comparison. At the same fan speed and ¼ horsepower
operating load, the Vari-Green unit required 220 watts of power and the P S C unit consumed
270 watts. With this information, we calculate the motor efficiency to be 85% for Vari-Green
and 69% for the P S C motor. This means that the P S C motor consumed 23% more energy -- and
this is at its most efficient operating point!
Now let's reduce the fan speeds by 30% and see what happens. As with the high speed test,
we'll observe the Vari-Green fan first. As the fan speed dial is turned, the fan speed
immediately slows and will level out at about 1,200 r p m. Notice that the value in the
watts display is dropping, too. As we reach our target speed, the input power is just
75 watts. The power decreased by 66%, as it should according to the fans laws.
Let's make the same speed adjustment to the P S C fan. As the fan speed slows down to
the 1,200 r p m target point, pay attention to the power input display. It isn't changing
much. In fact, as the fan speed stabilizes near 1,200 r p m, we can see that the input
power is reading about 260 watts. This is only a 4% reduction compared to the high speed
power consumption of 270 watts.
Again, let's document these results and look at efficiencies. The Vari-Green motor maintains
its efficiency of 85% regardless of the fan speed, and only needs 75 watts of power at
1,200 r p m. However, the P S C motor consumed 260 watts, plummeting in efficiency to just
24%. In fact, the P S C motor is gobbling up nearly 3 and ½ times the energy. Such
is the nature of the beast. As fan speed is reduced, a P S C motor converts an increasing
amount of input power into heat -- which, incidentally, leads to shortened motor life.
For the final demonstration, let's really dial down the speed on the Vari-Green fan
-- to around 20% of full speed. As the fan approaches 400 r p m, the Vari-Green motor
consumes just 5 watts of power -- and runs quiet and cool. Ideal for applications requiring
broad speed ranges.
As a summary, let's review our test data in a graphical format. As we observed, the P
S C motor draws nearly the same power regardless of fan speed and has a recommended fan speed
turn down of just 30%. The far superior Vari-Green motor is more efficient at high speed and
offers dramatic energy savings as fan speed is reduced. Savings range from 20% to more
than 70%, depending on fan speed. Plus, Vari-Green offers stable and cool operation down to 350
r p m.
More speed flexibility, longer life and much greater efficiency. Now that's Vari-Green!