Hot water is presently circulated through the building by two xxx hp pumps. These pumps were originally designed to deliver a constant volume of water to the heating system. The perimeter hydronic systems have recently been retrofitted with two-way control valves. The two air handling units with heating (SF-1 and SF-4) still have three way mixing valves.
Most of the time, the pumps are creating a higher than required head at a low flow.
It is recommended that a variable speed drive be installed on one of the pumps, and the speed be controlled to maintain a constant pressure in the system. It is also recommended that the three-way mixing valves on SF-1 and SF-4 be changed to two-way control valves, in order to minimize the necessary pump speed.
Issues and Concerns
For greatest savings, most or all of the control valves in the system should be 2-way.
Analysis text here