The ideal flow rate for a pool heat pump depends on the specific model and specifications of the heat pump, as well as the size of your pool. Generally, heat pump manufacturers provide guidelines regarding the recommended flow rates for their units.
The flow rate is typically measured in gallons per minute (GPM). It’s essential to match the flow rate of your pool pump with the recommended flow rate of the heat pump. This ensures that the water circulates through the heat pump at an optimal rate for efficient heating. Fortunately, most manufacturers have a pretty wide range of flow that will work well. To determine the ideal flow rate, you can check the documentation or user manual that comes with your heat pump. If you don’t have access to the manual, you can contact the manufacturer or check their website for specifications.
The heat pump that we recommend, the Built Right Pool Heaters’ 135kBTU models, require 30-70 GPM. Ideally, the flow rate will be in the middle of the range at around 50 GPM. At this flow rate, the heater will work the most efficiently, meaning it will use the least energy to heat your pool.
It may sound counterintuitive, but slowing down the flow does not allow the heat pump to transfer heat to the pool more efficiently. Yes, the water coming out of your pool jets may feel warmer, but it will be coming out slower, reducing the overall heating performance. Heat exchangers operate on a principle of Delta T, or difference in temperature. The larger the temperature difference, the faster the heat transfer. So you want cooler water running through the heat pump, meaning you want faster flow. There is a point of diminishing returns, however. After 50 GPM, the improvement in performance will be minimal, and you will just be using more electricity for your pool pump to gain negligible heating performance increases. If your flow rate is less than 50 GPM, your pool pump will use less electricity, but you will lose some heating performance.
It is important to note that pool heat pumps have a low flow shutoff. If the flow rate is not adequate, the heat pump will turn off to avoid overheating. This is a safety mechanism to protect the unit. The control panel will provide some indication that there is a flow error.
Keep in mind that the flow rate may also depend on factors such as the temperature of the incoming water, ambient air temperature, and desired pool temperature. Consulting with a pool professional or the manufacturer’s technical support can help you ensure that your pool pump and heat pump are properly matched for optimal performance.