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Converting a 2 pipe radiator system to a 1 pipe or staying with 2 pipe- Any thoughts

We are currently getting ready to add some radiant heat to an old Brownstone 1 family house and for the ground floor and 1st fl. The 2nd and 3rd fl are cast iron radiators. Standard cast iron radiators in the ballpark of 4 tube 26"-33" high of various lengths. On Monday I am going to measure up all the existing radiators so I have my btu load correct for that system. The current boiler is a Lochinvar Silent Knight. Was put in last yr thanks to Hurricane Sandy. (Not by us). The owner picked that boiler wisely for the upcoming radiant heating he planned on putting in. The heating system when completed will have 4 zones. (1) DHW, (2) in slab radiant, (3) staple up radiant to wood floor (watts flex plate system), and lastly (4) the existing cast iron radiators. Needless to say due to the renovation being done on the groundfloor we need to redesign the loop on the ground floor that feeds the radiators on floors 2 and 3. Originally i was thinking (1) pipe monflo tee system with tees on both supply and return. I should add almost every radiator supply and return originate on the groundfoor. But now as I consider the job I was thinking of going with a 2 pipe reverse return system. Like I said all heat sources are the same (cast iron radiators). They start approx 10-15' above the loop for the lowest floor and the top floor is approx. 25' . As for the radiant loops I will post another post about my thoughts of what I am going to use there . But for now any input on the existing cast iron radiator loop design would be greatly appreciated.


  • icesailor
    icesailor Member Posts: 7,265
    Reverse Returns:

    Two Pipe reverse returns ROCK. If all the radiator drops go into the cellar, I wouldn't connect them any other way. It will beat a Monoflow system every time. Just be sure that you are not confusing it with a direct return. In which case, the Monoflow might work better.

  • gennady
    gennady Member Posts: 831

    I would definitely not recommend monoflo. No way. I would organize system into type of load, high temperature, medium temperature and low temperature, and pipe them with primary secondary, high first and low temperature last on the flow. I would do separate outdoor resets for each load. Also, you mention on measuring radiators to determine load. How do you know those radiators are sized properly? What was the name and qualifications of the person who designed and installed them? Just do proper heat loss and remember radiant system produce lower air temperature and generally requires probably 30% less input than convection system.