Hi Guys- long story short had to reregister under this name since its been too long for my password to be saved. However- here is the situation. I have a Biomass 40 boiler that pumps out to the heating loop by way of a Taco 0010. At the loop I always had in the past to partially close down the ball valve between the boiler feed to the loop and its return to get any circulation through the loop. Each zone has its own Taco 009 Now, the colder it gets the more I have to fiddle with it and shut off zones to get any heat. Basically with this real cold weather I have shut down several zones and use a wood stove. It seems that this year is even worse when I replaced a 007 circulator on a zone. I have made sure there isn't any air in the system and tried to get information on why it is working this way. I ran a test with the propane boiler with a taco 007 circulator that is right next to the loop produces enough to run every loop with enough heat. Its obvious to me the 0010 circulator isn't producing enough pressure head or flow to work correctly. I ran the TACO pressure calculations and they show the 0010 should work, but they don't account for the Termovar mixer. I need to replace the circulator with something better. I looked at the TACO flow and pressure charts, and a 0012 and 0014 would have enough pressure and flow, but then I have to worry about too steep of a pump curve. So I'm looking for advice about the replacement TACO or using a three speed Grundfos or Grundfos Alpha in this to match up requirements better. thanks for the advice in advance!