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

Secondary loop sensor/Header sensor question

Mike_Y Member Posts: 9
I may be (am) over-thinking this but here goes: I will be installing a new condensing boiler with primary/secondary piping using a hydronic separator. The secondary loop feeds branch circuits of fintube radiators equipped with TRVs via monoflo tees. All the rads originate and return to the secondary loop. This monoflo loop was existing and worked great with the old boiler,ODR,TRVs and constant circ provided by a TACO 00e variable speed circulator. The new boiler will be a condensing unit with integral Outdoor reset. My overthinking is: do I need a secondary control loop sensor/header sensor for the ODR/control system to make sure the feed to the rads is what is needed for comfort? If I do, or if it is just prudent to include it, this will inform the choice of boiler I purchase. Currently looking at the Laars Mascot and Alta 120 or equivalent. Thank you all in advance.


  • Ironman
    Ironman Member Posts: 7,336
    It’s it needed? Probably not.

    Is it preferred? Yes, if you want more precise control and slightly more efficiency.

    I don’t see how this would affect your boiler choice as they all seem to have a system sensor available.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • hot_rod
    hot_rod Member Posts: 21,793
    Some boilers come with that extra supply sensor. Mount it 6" or so from the supply outlet of the hydro sep for best accuracy. Strap on sensor is fine. Or insert it into a well in a tee.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Mike_Y
    Mike_Y Member Posts: 9
    Thank you gents, both comments support where I was at. I greatly appreciate the resource that is this community.