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Grundfos 15/42 - Upgrade to something else w/ replacement?

TAG Member Posts: 755
Need to fix one of the manifolds on my oldest Buderus setup -- I'm going replace all the pumps while I have it apart. Panel radiators and radiant floor. The system has 3 15/42's for the heat zones and another for the indirect. Two of the pumps are blue -- so they are original (25 years old) . Replaced the primary pump and the one that feeds the indirect at some point -- could be 10 years ago. Is the 15/42 still the way to go? Looks like they use about 85w each -- the primary and floor mixing circuit run 24/7 in the heating season. The other heating loop is on a floor thermostat. I'm not looking for problems.

Also -- what's a good temp/pressure gauge? The original one lasted until about two years ago --- the Watts is already acting up (pressure). The Buderus was nice because it was a lower scale --- some have such a high temp and pressure scale the needle barley moves.


  • hot_rod
    hot_rod Member Posts: 22,271
    Any of the ECM circulators will save you some operating cost, typically 50% less electrical energy to move the same gpm, if that is of interest. I think the 15-42s are replaced with the 15-58 now.

    If you want to stick with that brand the Grundfos Alpha 1 would be about the same size in a higher efficiency style ECM.

    If you really want accurate gauges buy a good quality 0-30 psi pressure gauge, and a separate temperature gauge. I've yet to find a high quality combination gauge and the scales are really too course to get accurate data.

    I like a rear connection stainless case liquid filled gauge for pressure, and a Winters, Trerice or other top names for temperature gauge, digital if you prefer. Stay away from the economy gauge price range if you want accuracy.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • GW
    GW Member Posts: 4,704
    I like Alpha
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA