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Hi, Group. I'd like to see some discussion. I'm in a 3000 ft2 home circa 1928, with 20 year old boiler and mostly antique cast iron radiator heat. 3 different zones/pumps/thermostats. In the course of a remodeling project, I did staple-up radiant under the second floor master bedroom and love the results (had no heat before). Now I am working to add 2 more floor radiant zones under the main floor, based on what I can access in the crawl space or cellar.
I set up the floor radiant supply as a take-off from the boiler piping with a recirculating loop with 150F max. The floor radiant is recirculating loop with its own TACO pump, and draws more hot water from the boiler as needed. Boiler is set around 170F, I think. The TACO pump was sized to handle all my future radiant ideas, with plans to put in a control valve/T'stat for each of the floor zones. i.e. end up with 3 total floor radiant zones each with their own t'stat. When any floor t'stat calls for heat, he would open a nc valve and start the pump and send a signal to the boiler aquastat. If the boiler is under T, he starts up too. If the boiler is still hot enough from other uses, that's fine.
This is why I lie awake nights: With 3 different major zones, the furnace already runs a lot because they don't all call for heat at the same time. With the floor zone I already added, the furnace is on more, not less. (and in mild weather it seldom gets up to real operating temperature). So when I add 2 more floor zones, that means 6 different guys can ask for heat whenever they want. If it's really cold, the furnace runs a lot anyway and the heat is often satisfied from residual in the boiler without more fire. But normally it seems like the furnace will cycle a lot based on all these "little" demands.
WHAT IF I set up my 3 floor radiant zones on normally open valves rather than normally closed? That way whenever any of the 3 floor t'stats asks for heat, all 3 zones get 'topped up', meaning that it will be a longer down time before needing fahr again. Instead of a normally closed valve that opens when sensor is at 83, I'll have a normally open valve that closes when the sensor is at 85. What do you reckon?
I set up the floor radiant supply as a take-off from the boiler piping with a recirculating loop with 150F max. The floor radiant is recirculating loop with its own TACO pump, and draws more hot water from the boiler as needed. Boiler is set around 170F, I think. The TACO pump was sized to handle all my future radiant ideas, with plans to put in a control valve/T'stat for each of the floor zones. i.e. end up with 3 total floor radiant zones each with their own t'stat. When any floor t'stat calls for heat, he would open a nc valve and start the pump and send a signal to the boiler aquastat. If the boiler is under T, he starts up too. If the boiler is still hot enough from other uses, that's fine.
This is why I lie awake nights: With 3 different major zones, the furnace already runs a lot because they don't all call for heat at the same time. With the floor zone I already added, the furnace is on more, not less. (and in mild weather it seldom gets up to real operating temperature). So when I add 2 more floor zones, that means 6 different guys can ask for heat whenever they want. If it's really cold, the furnace runs a lot anyway and the heat is often satisfied from residual in the boiler without more fire. But normally it seems like the furnace will cycle a lot based on all these "little" demands.
WHAT IF I set up my 3 floor radiant zones on normally open valves rather than normally closed? That way whenever any of the 3 floor t'stats asks for heat, all 3 zones get 'topped up', meaning that it will be a longer down time before needing fahr again. Instead of a normally closed valve that opens when sensor is at 83, I'll have a normally open valve that closes when the sensor is at 85. What do you reckon?
