Up-Rated Versus Full-Rated Pumps and Motors
This is an area of confusion that can be fairly easily explained
What is the difference between up-rated or full-rated? Or is max-rated even better?
By understanding a few key concepts, you can clearly understand the difference and make an intelligent choice when selecting the proper pump and/or motor for your pool.
The Motor Plate
The motor plate will have two very important pieces of information
Horsepower (HP) – the horsepower rating of the pump
Service Factor (SF) – a multiplier factor
The Calculation
There is one simple calculation which tells the whole story
Horsepower X Service Factor = Total Brake Horsepower
If you multiply the horsepower rating times the service factor, you find out the total brake horsepower.
The total brake horsepower of the pump is real power rating of that pump or motor.
How Pumps and Motors Get Uprated
The motor plate above lists the following ratings for this 3/4 HP Full-Rated Motor:
Horsepower – 0.75Service Factor – 1.5
If we insert these factors into the equation, we end up with the following result
Horsepower X Service Factor = Total Brake Horsepower
0.75 X 1.5 = 1.13
Now, suppose you really wanted to take this motor and call it a 1.0 HP motor instead.
You would just INCREASE the Horsepower Rating and DECREASE the Service Factor.
HorsepowerXService Factor=Total Brake Horsepower
1.0X1.13=1.13
VOILA . . . that 3/4 HP Full Rated Motor is now classified as a 1.0 HP Up-Rated Motor
EXACT SAME MOTOR . . . DIFFERENT HORSEPOWER RATING
Some Examples from Motor Labels
The following chart for square flange motors shows how the same motor can be given two different ratings. These motors come off the same assembly line. The only difference is the label that is glued on the motor at the factory.
| Motor | Horsepower | Service Factor | Total Brake Horsepower |
|---|---|---|---|
| 3/4 HP Full-Rated | .75 | 1.5 | 1.13 |
| 1.0 HP Up-Rated | 1.0 | 1.13 | 1.13 |
|
These two motors are the exact same thing |
|||
| Motor | Horsepower | Service Factor | Total Brake Horsepower |
|---|---|---|---|
| 1.0 HP Full-Rated | 1.0 | 1.65 | 1.65 |
| 1.5 HP Up-Rated | 1.5 | 1.1 | 1.65 |
|
These two motors are the exact same thing |
|||
| Motor | Horsepower | Service Factor | Total Brake Horsepower |
|---|---|---|---|
| 1.5 HP Full Rated | 1.5 | 1.5 | 2.25 |
| 2.0 HP Up Rated | 2.0 | 1.13 | 2.25 |
|
These two motors are the exact same thing |
|||
| Motor | Horsepower | Service Factor | Total Brake Horsepower |
|---|---|---|---|
| 2.0 HP Full Rated | 2.0 | 1.3 | 2.6 |
| 2.5 HP Up-Rated | 2.5 | 1.04 | 2.6 |
|
These two motors are the exact same thing |
|||
An Example From Pump Curves
If the point is not perfectly clear from the motor ratings, take a look at the pump curves. All the manufacturers pretty much do the same thing. The 3/4 HP full rated pump comes off of the exact same assembly line as the 1.0 HP up rated pump. All the parts are the same. The ONLY difference is the label.
Check out this pump curve from Sta-Rite (we’ve added a little color to make it nicer looking.)
 |
Notice how the 3/4 HP Full Rated and 1.0 HP Up Rated pumps use the same flow curve . . . that’s because they are exactly the same pump. |
THE BOTTOM LINE
THE BOTTOM LINE . . . the actual horsepower rating of a pump or motor does not really tell you much.
When it comes time to replace a motor . . . you MUST consider both the horsepower and service factor. This is the only way to insure that you are getting the motor that you need. Consider also the frame size and type of the motor as well. Don’t forget to get a pump seal and appropriate gaskets as well.
When you are replacing pump parts such as an impeller or diffuser . . . make sure you match up the exact part number or you may end up with a mismatched impeller or diffuser.
When it comes time to replace your pump . . . look at the flow rating. Pay only mild interest to the HP rating.