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Hot water recirculation system

Shane_McCafferty | Posted in General Questions on

A couple years ago we purchased a Navien combi-boiler (NCB240E) to provide DHW and to heat our home (radiators).  This unit replaced an old inefficient oil-fired boiler that was costing us a fortune to run due to the high price of heating oil and the lack of insulation in the home.  We are about to begin a major renovation in which we will be improving the building envelope and upgrading the HVAC system.  
We originally intended to run in-floor radiant heating (which could’ve been accomplished with the Navien unit we bought) but we’ve since opted to run a multi-zone mini-split system.  So the portion of this unit that was dedicated to heat the radiators will no longer be used.    
We have a fairly large home (3,000 sqft slab on grade main floor plus 1500 sq ft second storey) with hot water demands at each end of the house.  I’ve read Gary Klein’s article on Efficient Hot Water Piping and I’m considering a zoned trunk and branch system with a recirculation pump.  Can this combi-boiler unit be somehow used as a hot water recirculation system?

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Replies

  1. Expert Member
    AKOS TOTH | | #1

    Their drawings show how to set up the pump and sizing:

    https://www.navieninc.com/app/W1siZiIsIjIwMTgvMDgvMjMvMTkvNTgvNDQvYjJmN2U0NGEtNjZmMS00NjhlLWJhNGYtZjZkZjUxMjNjNjQ1L05DQi1FIEFwcGxpY2F0aW9uIERyYXdpbmdzLnBkZiJdXQ/NCB-E%20Application%20Drawings.pdf?sha=9333d3f42dfea666

    One thing with combi is that you don't want the recirc to run for extended period of time as this will cause the unit to short cycle.

    Make sure the system you install is one of the adaptive systems (ie Taco smartplus, or Grundfos PM Auto) or one that is triggered by motion sensors in each bathroom.

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