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How to Size a NFPA 13D residential pumping system

Don’t Get Stuck on Horsepower When Sizing a 13D Pump System!

A typical call to our customer service staff regarding our 13D pumping systems starts like this, “I’m working on a 3,000 square foot house, what horsepower pump do I need for the sprinkler system?” This question assumes that square footage and horsepower are the primary factors in sizing the pump for the system – simply put they are not.

When sizing motors horsepower is the measuring stick. A bigger motor means more horsepower, and more horsepower means more power. Simple, and for the most part true. However, when you add an impeller and casing to a motor and set it to moving water the motor becomes a pump – and the rules change slightly but significantly.

Obviously a 2 horsepower pump will not pump as much water as a 10 horsepower pump, all pressure requirements being equal. However there are many instances, when comparing different lines of pumps, where a 2 horsepower pump will pump more water than a 3 horsepower pump. This is because in the world of pumps the impellers efficiency in conjunction with the motor defines how much water the pump can deliver, not the just horsepower of the motor.

What Factors are important when sizing a 13D pump system?

Flow (GPM), pressure (PSI) and cost are our guiding factors.
We first ask our customers for the flow and pressure required to meet the demands of the system – these are determined by the hydraulic calculations done during the design phase and should be readily available. The pressure and flow give us the parameters we need to select the least expensive pump we offer that meets the demands of that particular home.

To get a better idea of this process click on one of the links below to view the pump selection chart on page two of our RFP System cut sheets.

Proper pump selection is a fairly complicated process when done properly. When you call General Air Products for a quote on a 13D pump system simply provide us with the pressure and flow required then leave the rest to us. We will respond with the most efficient and cost effective solution available. In short we will get it done right.