Pump Affinity Laws and Energy Savings

Pump Affinity Laws and Energy Savings

As originally published on Pentair.com

Are you looking to save energy, cut costs, and support the environment? We believe that every pool owner can answer “yes” to this question—especially as energy costs continue to rise and the desire to be more environmentally friendly increases.

With pool pumps consuming a vast majority of your pool’s energy, switching from a single-speed to an energy-efficient, variable speed pool pump is a good place to start saving on costs and working towards energy efficiency. But how does that work? The answer is all in the laws of physics – Pump Affinity Laws!

Pump Affinity Laws are designed to govern the performance of your pump. The purpose of deriving these laws is to help you predict pump performance at different velocities or speeds and modify your pump for various duties. In other words, they’re designed to help you predict the impact of speed changes on your pump.

So how do the Affinity Laws work? Affinity Laws use physics (more precisely, the Buckingham π theorem) to predict how changes in velocity will affect the pump’s head, flow and power requirements. The Affinity Laws are often complex and confusing and require entire engineering classes to master, but here’s an easy to understand breakdown of the math:

FLOW: “The flow (GPM) varies proportionally with the change in speed.” For example, 2x speed = 2x flow or ⅓x speed = ⅓ x flow.

HEAD: “The pump head (pressure) varies with the square of the change in the speed.” For example, 2x speed = 4x head (22= 4).

POWER: “The power requirement (horsepower or kilowatts) varies by the cube of the change in speed.” For example, 2x speed = 8x power (23= 8).

With these equations, you can input your pool’s system head and flow requirements to determine the most efficient pump and speed. The benefit of using Pump Affinity Laws is that they help pool owners save on energy costs.

We don’t expect you to know how to do this yourself, so we’ve put together the Residential Pool Pump Savings Calculator to help you determine how much you can save with a variable speed pool pump. All you have to do is put in the size and shape of your pool! We’ll do the math for you.

So, what will I save by switching to from a single-speed pump to a variable speed and flow pump?  Variable speed and flow technology is designed using Pump Affinity Laws to determine the most efficient point of operation based on a given application. As a result, variable speed and flow pumps can save pool owners up to 90% in energy costs. At the same time, variable speed pumps can run longer and slower than a single-speed pump. And according to Affinity laws, when you reduce the pump speed in half, you cut consumption by 87%.

Besides cutting back your energy bill, using an energy-efficient pool pump is crucial for supporting the environment and there are currently available rebates on select variable speed pumps! Now’s a great time to make the switch to variable speed technology!

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