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Q&A: How do you size and select a circulation pump?

A circulation pump is a device that moves fluid through a closed-loop system, such as a hydronic heating or cooling system. To size a circulation pump, you need to know the following information:

– The heat load or cooling load of the system, in BTU/hr or watts. This is the amount of energy that the system needs to transfer to or from the fluid.
– The temperature difference between the supply and return fluid, in degrees Fahrenheit or Celsius. This is the amount of heat or cooling that the fluid gains or loses in the system.
– The head loss or pressure drop of the system, in feet of head or meters of head. This is the amount of resistance that the fluid encounters as it flows through the pipes, fittings, valves, and other components of the system.

Using these values, you can calculate the required flow rate and head of the circulation pump using the following formulas:

– Flow rate (Q) = Heat load / (Specific heat x Density x Temperature