Adapted from an article by Steve Goodale of Aqua Magazine
Pool pumps use a lot of power, and as a result, they must dissipate large amounts of heat as part of normal operation. Combine that with the fact that most pool pumps operate in direct sunlight during the hottest part of the year, and you have the potential for an overheated motor.
If your pump is experiencing problems and is under 7 years old, there is a good chance it is overheating; caused either by an electrical problem or friction. While electrically related failures are by far the most common cause for pump overheating, there is also the potential for a friction fire to develop if a pump is starved for water.
How Hot Is Too Hot?
All electric motors run hot and pool pumps are no different. But how hot is too hot for a pool pump? The first test is simply whether you can touch the motor or not.
Under normal operating conditions, the motor end of the pump is hot enough that you can barely touch it — but not searing hot. If your pump is so hot that you cannot even rest your hand on top of the motor, it may be a sign that something internal on the pump is failing.
Once a heat-related failure is experienced, a downward spiral effect has started that will most likely result in the pump failing completely. Before a pump will turn itself off (thermally disconnect), the problem will need to be fairly severe. It is not uncommon for pumps with heat damage to run for a few days, up to a year or more, before they finally deteriorate to the point that you will need a new pump.
What Causes Heat Build-up?
There are many reasons why your pump might be generating extra heat; these four are the most common:
Friction. There are multiple moving parts inside of a pool pump. Any moving part will generate heat from friction. Under normal conditions this amount of heat does not pose a problem for pool pumps as they will self regulate their heat. Ambient air is drawn through the motor to help keep it cool, and heavy pieces of metal (heat sinks) are designed to safely absorb heat that builds up.
One of the most common ways pool pumps will generate friction is from corroded or rusted bearings inside the pump. The telltale sign of rust on your pump bearings is a high-pitched squealing sound. The main cause for worn out bearings is a leaking pump. If you see any leaks, have your pumped looked at right away to prevent bearing failure.
Lack Of Airflow. In order for most common electric motors to stay cool, air must be drawn into the motor and over the electric windings. This relatively cool air pulls heat from the motor before passing out the backside of the pump. This is why these types of pool pumps should only be installed in areas with sufficient airflow.
If you install a pool pump in a very small closet, or any kind of enclosed space, you will dramatically reduce the service life that you can expect from the pump. The motor will still draw in air but the air inside the closed space will soon be heated from this energy transfer. If the air inside the pump location is too warm, it will no longer be able to effectively cool the motor.
Suction-Side Restrictions. When the water coming into the pump is coming from a long section of pipe, the flow restriction is greatly minimized which means the pump doesn’t have to work as hard to suck water into it. This is especially important if you have a pump that pushes a high number of gallons per minute (GPM). Slow-moving water flows smoothly and has the minimum amount of friction loss. As water moves faster, and becomes more turbulent, the efficiency of how the water moves through the pipe drops. Having a 90-degree fitting, elbow, check valve, union or ball valve directly in front of the pump’s suction side will dramatically increase the turbulence of the water, which will result in efficiency loss for your pump.
Pressure-Side Restrictions. It’s also critical to minimize resistance on the pressure side. Taking a large pump with a 2 or 3 hp motor and forcing the flow through a heavy-flow restriction — such as a filter that is too small for the pool or a small pipe size — will cause the pump to work harder than it needs to. Picture yourself on a bike riding as fast as you can. If you are riding into a strong headwind, your performance and speed will drastically decline, and force you to use more energy to compensate. The same thing happens to your pump when you have pressure-side flow restrictions.
If you think your pump isn’t doing the job it should to circulate the water in the pool, ask your pool professional to inspect your pump and determine what should be done. Be aware it may mean a new pump that better fits your pool needs and/or a new installation of the pump to improve performance for the long term.