Published by Matt Fichera on 04/02/2020
Saving Money With Pump Affinity Laws
Why should I use a variable speed pool pump? This is a great question to ask. Variable speed pool pumps reduce power consumption, take money off your monthly power bill, and they’re “green” having less impact on the environment when compared to other models. These are all great things and good reasons to invest in a variable speed pump.
Your pump is the number one consumer of power related to the swimming pool and is typically second behind any kind of heating or cooling for power consumption related to your household overall. With this in mind, energy costs on the rise, and an increase in being more environmentally conscious, switching from a single-speed to an energy efficient variable speed swimming pool pump is definitely the way to go!
But how does a variable speed pump actually save you money? The short answer to this question is laws of physics, Pump Affinity Laws to be more precise. This set of laws are what governs your pump’s performance and work to modify your pump for various duties. These rules help you with predicting motor speed changes and how they impact your pump and its functionality.
The Pump Affinity laws use an existing physics law called the Buckingham π theorem to forecast how the pump motor’s speed fluctuations affect the pump’s head, flow, and power requirements. There’s no doubt that these laws and the math behind them can be quite confusing and complex but the following is a breakdown of how all of these work.
Flow: “The flow, Gallons Per Minute (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).
Within the parameters, you are able to provide your pool’s head and flow requirements to mathematically determine the correct pump and speed. By utilizing these, it saves you on energy costs in the long run. Never fear, many manufacturers are more than happy to do the math for you on their website. All you typically need is to know and input the size and shape of your pool and the calculator will determine how much savings you’ll receive by switching over to a variable speed pump. Making the switch can save some pool owners up to an incredible 90% in energy costs. Variable speed pumps run longer and slower than a single-speed pump on purpose as according to Affinity laws, when you reduce the pump speed in half, you cut consumption by 87%.
In addition to all of these savings, many manufacturers offer limited time rebates off the cost of their VS pumps. There are also many state run groups that offer rebate programs, where you submit proof of purchase and they issue you back a check for a certain percentage of the overall cost. A quick Google search usually determines if your state has a program.
Now is a great time to make the switch to a variable speed swimming pool pump.
