In fairness to all, we don't discuss pricing on the Wall. Thanks for your cooperation.
mod-con boiler as back up
I am looking at using an OWB to heat a 20-30 gallon buffer tank through a heat exchanger. The buffer tank will feed the radiant floor pex system. When the OWB is off, I want to use a mod con on-demand propane boiler to take over in a re-circulating loop with the 30 gal buffer tank and the radiant system:. (6 loops of 1/2 inch pex each 250 feet long)
A Quietside 120 ODW mod con can accept input water as high as 120 degrees but requires at least 29 psi input at peak demand. A Taco-9 recirculation pump delivers 8 gpm at 34 feet of head and is recommended by Micheal Chandler in a similar system.
Question: Would this pump provide the 29 psi needed by the mod con?
Is there a formula that includes gpm, head, friction, pipe size....to calculate psi?
(From what I have read, mod-cons are generally not used in closed systems because of the pressure requirement)