There are several factors to consider when purchasing a circulator pump. These include Horsepower, flow rate & head loss, material, connection method, features, and brand.
Horsepower
Horsepower or HP refers to the strength of the motor in a given pump. Horsepower is one of the most important considerations when selecting a circulator pump. A pumps' horsepower may vary from 1/40 HP for small pumps to several horsepower for large commercial pumps. Horsepower directly affects the flow rate and head loss characteristics of a pump. Only within the same brand does higher horsepower indicate a more powerful pump. When comparing pumps from different brands, you must consider both horsepower and RPMs to choose a pump with the appropriate power based on gallons per minute (GPM) and head loss of your system.
Flow Rate & Pressure Loss
The flow rate of a pump is defined as the gallons of liquid a pump can move in a minute (GPM) given a certain head loss pressure. The appropriate pump will be able to reach the required flow rate while overcoming the systems' head loss. A pump curve, which displays head loss figures on the y-axis and flow rate on the x-axis, is commonly used to find the correct pump
Material
Circulator pumps may be constructed out of cast iron, bronze or stainless steel. Cast Iron pumps, such as the Taco 007, are the most common in heating applications where oxygen-barrier PEX tubing is used. With no oxygen barrier in the tubing, bronze pumps may be required in heating applications to prevent rusting. In plumbing systems, bronze or stainless steel pumps must be used.
Connection Method
The most common way to connect a pump is with flanges. Flanges are used to make a threaded or sweat connection between a pump and the supply pipe leading to it. Common sizes of flanges are 3/4", 1", 1-1/4", and 1-1/2". Cast iron and bronze flanges are available and should be purchased to match the material of the pump being used. Recent innovations in flanges include shutoff valves and drains. These types of flanges may be purchased to ease installation, but are not required.
Pumps may also be connected using sweat or threaded connections. The pump will specify if it may be connected in this manner.
Features
Circulator pumps may come standard or with several additional features. The two most common features are an integral flow check (IFC) or variable speed. The Taco 007-IFC is an example of a pump that comes with an integral flow check. The placement of the flow check in the pump ensures that it won't be needed elsewhere in the system. A variable speed pump such as the Taco 00R-MSFIFC has the ability to operate at several different speeds. These pumps are commonly used in radiant heat systems.
