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What is normal flow rate for infloor radiant?

I have recently replaced our old boiler with a 120k btu combi-boiler. The circ pump was also replaced with a Grundfos pump. Our home is 2000sf and we have 5 zones. The combiboiler burns propane. The new boiler seems very efficient, as my propane usage is greatly reduced. But I notice that the circ pump (in autoadapt mode) is only pumping 1gpm if one zone is calling for heat; 2 gpm if 2 zones are running, and so on. I’m a novice, so I’m wondering if that amount of flow is correct/normal? It doesn’t seem like a lot. I’m noticing that the zone farthest from the boiler is not getting very warm (it did before the upgrades). I suspect that by the time the water reaches this zone, it has cooled down. Looking for advice please.


  • Zman
    Zman Member Posts: 7,355
    I would not put a ton of faith in the circulators estimated GPM, in reality it is probably +/- 30%.
    As far as flow rates go, the correct flow rate depends on a few variables. Most residential systems perform well with a flow rate > .5 GPM per loop.
    I have found the autoadapt feature to be problematic in when used in radiant systems. CP2 or CP3 usually works better.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
    Alan (California Radiant) ForbesSTEVEusaPAgordonbone