I am running several ECM's for a retro-commissioning project. One of these ECM's is to put a VFD on the heating water pump. When I do this in eQuest, it decreases the electric consumption but increases the gas consumption resulting in a net increase in annual energy consumption. I have gas fired boilers providing heating for the building. I have run some hourly reports and it looks like the single speed pump is adding more heat to the water loop than the pump with the VFD. This seems reasonable to me, but it doesn't seem like it would result in more energy use than it would save. Could you shed a little light on this subject for me?

Thanks,

Tim Johnson, EIT, LEED AP