It is well known that pumps are oversized for almost all applications. This is true worldwide, for both industrial and commercial installations. A major reason for HVAC pump oversizing and the resulting power waste is fear of flow unbalance (short circuiting)--and a consequent lack of flow for some terminal units.

The purpose of this discussion is to illustrate simple circuit flow analysis techniques that will enable design engineers to identify and provide protection against short circuiting for new design. Removal of short circuit fears should help reduce the tendency to oversize pumps. The analysis technique will also establish methods for flow balance in existing buildings and permit a considerable reduction in pump power requirements.