Yanche wrote:The engineer in me needs to tell you that these pumps are really inefficient. They use split phase permanent capacitor run motors and have lousy starting torque. Only about 30% of the electrical energy gets imparted to the rotor as mechanical work. That said they are an economical reliable choice for residential applications. I use them myself in zoning and primary-secondary piping.Edit: efficiency is 16.9%, see edited post above
Is there a more efficient and better performing --but presumably higher price--alternative available/
The overall efficiency of a circulator is the sum of the centrifugal pump efficiency and the motor efficiency. Pumps with small diameter impellers have lower efficiencies. Large pumps, much larger than those used in residential application, also have diffuser vanes that are missing in residential sized pumps. These vanes improve pump efficiency. So for residential applications we are stuck with the low end of the centrifugal pump efficiency.
The electric pump motor is another story. Fractional HP circulator pumps are available with standard non-integral motors. Unfortunately most are sold with split phase electrical motors, the lowest efficiency of all motors. Some are available with special order motors. The Taco Series 110-120 is one such example. See:http://www.taco-hvac.com/en/products/In ... d_id=15552
You would want to specify a capacitor start, capacitor run induction motor for highest efficiency. I have no idea what the relative cost would be.
This is all an academic exercise because the amount of electricity saved with a special order pump would likely be small compared to it's purchase price. The electronically speed controlled wet rotor circulator pump might have high efficiency. With proper electronics the normally split phase motor can be made to operate like a capacitor start, capacitor run motor. I'll leave that evaluation to another student of circulator pump efficiencies.
Edit: I looked up the efficiency of a large circulator pump, Taco TA Series Model 0538, efficiencies are 45 to 63%
depending on operating point. 63% at 200 gal/min & 75 ft of head. Just what's needed to get that Outdoor Furnace Water through the 1/2 inch underground PEX.