Click here to Find a Contractor in your area.
Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit

Boiler zone controller with variable speed pumps?

Have a new HW boiler plumbed in. No DHW. Two heating zone pumps.

The boiler (Vitocrossal 300, CU3A) has a variable speed (VDC) logic built in to control a single circulator pump.

Is there an integrated controller that combines the 2 thermostat/zone pump controller with the variable speed output signal from the boiler itself such that both zone pumps can be run at variable speed per the boiler logic?


  • tc60045
    tc60045 Member Posts: 31
    No secondary, just a primary loop?
  • zoom
    zoom Member Posts: 72
    Two loops, one for upstairs one for downstairs. I have not designated either as primary at this point.
    HVACNUT Member Posts: 4,197
    @tc60045 was referring to Primary/Secondary piping.

    Can you post some pics of the boiler and connected piping?
  • Steve Minnich
    Steve Minnich Member Posts: 2,674
    P/S would typically be unnecessary with a CU3A. Flow through the boiler isn’t a problem. The water capacity of that boiler is more than most cast iron boilers.
    Steve Minnich
    Minnich Hydronic Consulting & Design, LLC
    [email protected]