Retrofitting a circulator for a load that has changed

Tom Hopkins

I have a retrofit application that need a new circulator because of some changes in the load. The original installation had one main valve with thermostat for each manifolds. Then, the system was changed to have small valve actuators with thermostat for each of the radiant tubes in the manifolds. What would be the best way to calculate the new load that would include the head lost of the new valve actuators?

Can I simply open the thermostats in the rooms and see what pressure head I get at the pump? Then using this pressure head and the original flow find a new pump curve that would do the job.