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Panel radiator system design options
I’m putting an addition on my house and now its time for a new heating system. Old part of the house has a massive oil fired forced hot air setup with some interesting ductwork. We just installed a gas line and I’d like to switch everything over to steel panel radiators with a TRV on each one, no central thermostat in the house. Total heat loss for everything is 40k btu/hr (house will be 1900 sq ft ranch). Room heat loss numbers range from 500 btu/hr (small bathroom) to 9500 btu/hr (living room).
The piping for the radiators would be 3/8 pex home runs to each radiator, 2 manifolds (13 or so total radiators), fed by an Alpha pump (or maybe a Wilo eco with its slightly lower curve). I’m currently sizing the radiators for 150° supply at design conditions. I’ll be having my plumber do the install but I want to make sure I understand everything and have the system set up how I want before the work starts.
My big question is which boiler option is the best-
Option 1- HTP pioneer boiler, run with outdoor reset and jump the TT. This is probably the easiest, no short cycle issues with the small zones. The boiler would just work to maintain the tank temperature. If there is only small demand the pump can pull warm water out of the tank without the burner firing.
Option 2- A low mass mod con (probably an HTP UFT-80) piped into a buffer tank. Not sure what the best way to control this would be, maybe a tekmar outdoor reset with a temperature sensor in the tank to fire the boiler? That way the boiler is just controlling the tank temperature as the system needs it. Outdoor reset would be disabled on the boiler and run through the tekmar. I’d need an additional circulator to feed the tank. Would this work? Am I missing anything obvious here?
Is there any large upside or downside to either one of these options? I like option 2 better because it gives me a better option to also run an indirect tank for DHW, but it is a more labor intensive install and I’m not sure if I’ll have any control issues.
I know this is probably over simplified so feel free to tell me where I’m wrong and what the better option would be. Thanks for the help