Divert or not to divert

Spag74

Customer wants to split a one pipe diverter tee into two zones because radiant heat was added where tile floors are and it causes the T-stat on first floor not to turn on which makes rooms on second floor to be cold. If the one pipe is split into 2 zones: Can I supply the 1st floor with a 3/4” line from the boiler and tie into 1” that feeds radiators & returns back to the boiler? The first floor would have 7 cast iron radiators on that zone. The original tee system had an 1-1/4” main from the boiler and ran to the front of the house. It reduces down to 1” and splits in half picking up CI radiators on both sides of the house and returns back to the boiler Second floor will have 5 cast iron radiators which should not be a problem with 3/4” diverter tee zone Work sounds redundant but if they want it and pay for it no issues here Please give feedback I recommended moving t-stat to the 2nd floor which will be the cheapest and less labor intensive but that might cause the first floor to be to hotter with RH. I guess process of elimination will be the deciding factor

Jamie Hall

You have no zones? This is all one zone? You will indeed need to split into two zones, perhaps as you suggest. You will also need to control the two zones separately -- so you'll need an additional second floor thermostat for that zone.

Spag74

It’s adequate  to supply the first floor zone with 3/4” from the boiler and tie into a 1” line that supplies the radiators and returns to the boiler?
That zone will have 7 cast iron radiators 

EdTheHeaterMan

Moving the thermostat to the second floor will solve your second floor insufficient heat problem.  And you are correct in assuming the first floor will overheat. It is easy to solve the overheating radiator problem if the radiator valves are in working order. On a diverter T system, you can slow down the amount of heat into those radiators by throttling the valve closed. In order to get it just right it will be a trial and error adjustment.