Should my pumps be 4-pole or 2-pole?

The question often arises in HVAC pump selections- Should my pumps be driven at 4 pole (1450rpm nominal) or 2 pole (2900rpm nominal) speed?

Traditionally consulting engineers always specify 4 pole. This has and always will be good practice where the duty allows, but before deciding on this, one should consider several factors listed below:

The Operating Hours, Life Required and Downtime for Repairs

The main wearing parts on a pump set are mechanical seals, pump bearings and motor bearings.

The client usually expects a reasonable life with minimal maintenance i.e. a low Life Cycle Cost. To achieve this, one should consider operating hours and speed at the same time OR the total revolutions in the life of the pump. A pump which runs long hours is best selected at a lower speed than a pump which...