Introduction to Variable Speed Pumps

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Complete introduction to variable speed pool pumps

The pump is your pool’s heart and the centerpiece of its circulatory system. Even with the best chemical support, the only real way to keep a pool clean and pleasant to swim in is by keeping the pump running regularly – filtering the pool’s water through both an external skimmer and an internal filter medium, and pumping filtered pool water back into the basin.

Yet as with most pool components and installations, pumps come in all shapes and sizes. And while the best pump for you depends on a number of circumstances, many pool owners are making the switch towards variable speed pool pumps over the old single speed and dual speed pumps. Let’s see why.

What is a variable speed pool pump?

If you’re reading this on a computer or phone, your device runs on a processor that regulates how much power it uses in much the same way a variable pump does. Processors are programmed via your device’s motherboard to use dynamic frequency scaling to adjust their clock speeds and conserve power or boost performance, depending on what’s currently needed. A slower processor produces less heat, and slows down internal cooling (fans), producing less noise.

When more oomph is needed, the clock speed ticks up, and the fans get louder. Processors are rated by their maximum clock speeds and number of cores, but they don’t always run at 100 percent load. This would take up way too much energy, produce an ungodly amount of heat, and would kill your device’s longevity.

Pool pumps also function on a set speed, which refers to the RPM (rotations per minute) of the pump’s motor shaft. Most older pool pumps are either single speed pumps or dual speed pumps, meaning they either function at a set RPM (which means they’re always set to one speed, and cannot be adjusted) or two different speeds.

Variable speed pool pumps, as the name implies, automatically alter their own pump speeds based pre-programmed settings and pressure sensors, allowing you to be much more efficient with your power without sacrificing the option of pumping at a much higher rate when needed.

Variable speed pool pumps vs. single speed and dual speed pool pumps

Single speed and dual speed pool pumps come with one or two set pump speeds out of the box. On dual speed pumps, you can press a button or twist a knob to kick the motor up or down. While dual speed pumps let you be a little more efficient (and less noisy), two speeds isn’t really enough to take full advantage of the energy efficiency of a variable motor.

Variable speed pool pumps adjust the RPM of the pump via a programmable controller, which can also automatically adjust pump speeds based on pressure and flow rate (calculated based on provided information, including the pool’s size, and how many times you want the pool to be completely turned over (i.e. totally filtered) per day.

How does a variable speed pool pump work?

Pool pumps work via an electric motor. These convert electricity into mechanical energy via a stator and rotor, creating torque (a measure of force over distance) to rotate the motor shaft. An impeller attached to the motor shaft is what ultimately moves water through the pump via rapid spinning.

The pump’s speed is measured via its rotations per minute (RPM). Pool pumps are also measured by horsepower, which is expressed by torque x RPM / 5252. In other words, a pool pump with 1 horsepower and 3 ft/lbs of torque has 1800 RPM. To make things even more confusing, note that you can also measure torque in Newton-meters rather than foot-pounds.

This is to say that all pool pumps function based on their motor, and the force it translates onto the impeller. Where a single speed and dual speed pump only has one or two settings, variable speed pool pumps use processors to control the speed at which the shaft rotates, by controlling the amount of power fed into the motor.

Variable speed pool pumps allow you to run your pump at a much, much lower RPM than usual for most of the time, thereby massively cutting into your energy costs by drastically cutting down on the kW (kilowatts) your pump is eating.

Variable speed pool pumps can be programmed to work in different ways, such as kicking in at a slow 600 RPM, and working their way up to higher speeds over time. This has the benefit of being much quieter while saving you a lot of power.

Pros and cons

Let’s go over some of the pros of switching to a variable speed pool pump. They include:

  • Lower energy costs.
  • Pump longevity.
  • Much less noise.
  • Built-in programmable fault detection (often including a pressure sensor that tells you when the filter needs cleaning).
  • Can be kicked up to pump faster.

However, there are also cons to consider. In particular:

  • More expensive to purchase and install.

There’s no question that variable speed pool pumps are more expensive than older single-speed models. However, it should be noted that pool pumps are a serious investment in general, and because you’re saving a lot of dollars on those kWs, you do end up eventually getting back the difference (and saving in the long-term), especially if you leave your pump running for several hours every day, as you should.

With the market being so varied, you might also have trouble finding the right pump for you. Not only do you have to take pool size and flow rate (based on your piping and filter) into consideration, but you have a selection of additional features to consider as well. Some variable speed pool pumps come with anti-freezing technology to prevent pipe bursts during winter, for example.

Choosing the right pool pump for you

When you’re in the market for a new pool pump, you will want to know a few things about your pool:

  • What voltage is your current pool pump running on?
  • What are your pipe sizes?
  • How large is your pool?
  • Do you need a top-mount or side-mount pump?
  • And more.

When in doubt, consult the pool professionals.