Up Rated vs. Full Rated Pumps & Motors

Up-rated and full-rated are terms which are used in order to describe the motor's service factor. Its service factor is given a numeric value which determines the THP, or total horsepower, of the motor.

This particular rating system started in the mid-20th century when the service factor was used in order to rate home water systems. In many areas, the older electrical systems had low voltage conditions and were somewhat unreliable. NEMA standards took these low voltage conditions into consideration and made the service factors for these motors higher. As the pool industry started to progress, NEMA started to apply these same standards to swimming pool pumps.  The pool market eventually ended up with low service factor, referred to as "up-rate", and high service factor, referred to as "full-rate", motors.

The motor's total horsepower is calculated with the formula that is presented as follows:

Horsepower (HP) x Service Factor (SF) = Total Horsepower (THP)

The following examples were taken from a few common pool pump motors and will help to better illustrate this formula.

(The Horsepower rating is the same, but the THP is different)

(The Horsepower rating is different, but the THP is the same)

The B2847 and SQ1102 are shown as full rate motors.

The B2853 and USQ1102 are shown as up rate motors.

Both the "Up" and “Full” rate listings are based strictly on the service factor of the motor. According to NEMA, in order for an HP motor to be considered full-rate, its service factor must be equal to or higher than the listed full rate service factor. The motor is considered to be up-rate if it has a service factor that is lower than the listed full-rate service factor. The chart below demonstrates how the full- rate service factors are not necessarily the same for all horsepower motors. Let’s take a look at a few full-rate service factor motors. (Keep in mind that full rate motors sometimes have higher service factors.)

What’s important to understand here, is that total horsepower is the most crucial element. When you replace your motor, you should determine the total horsepower by checking both the service factor and the rated horse power together. A motor that has a full-rate and lower horsepower but a higher service factor may be just as powerful as a motor that has an up-rate and lower service rate.

If you replace your motor with one that has a lower total horsepower than the original, then you may have to deal with overheating and filtration that is not as efficient. In the same way, if you replace your motor with one that has a higher total horsepower than the original, you will risk overworking your filtration system because the motor will try to pump more water than your system was actually designed for. It is much easier to find the best motor when you match the total horsepower to the original motor’s total horsepower.

We here are Sunstar Alliance always recommend replacing your motor with exactly the same motor that you had.  This makes sure that the motor will fit correctly and work properly with the impeller.