Hi All,

I am trying to model a recirculation pump with a variable speed drive for a domestic hot water loop, however, have not been able to control the pump as expected. From my understanding of the technology, the point of having a VSD on a recirculation pump is to be able to modulate the flow of the recirculating water so that a desired temperature is maintained at the end of the supply portion of the loop (say 105 F since that is what most people want for showering). This way you can save both water heater consumption and pump energy. However, I do not see a way to specify this type of control in eQUEST.

Whenever I set the drive type to Variable Speed, I get a consumption reduction as anticipated, but the part load profile shows that it is simply at 50% the entire time (see image attached) rather than varying with the system/environmental conditions as expected. I have the control type set to Load Reset and the Min Alarm Temp set to 105, which matches the Loop Delta T specified of 25 F (supply temp 130 F). Changing the loop delta T and the Min Alarm Temp has no impact on the operation of the pump. Thank you in advance for any insight you may be able to offer!