Cast Iron Radiators

larry_9

I came accross a customer who has cast iron radiators and wants to put a geothermal heat pump in and use it instead of a boiler to heat the house. With the discharge water we would be supplying 118 degree water, returning with 98 degree. I was wondering if the heat could maintain the level of comfort that they have with this system or if I would have to add more basebroad. I found that cast iron basebroad is 3.4 linar feet EDR at 1 pound steam pressure but what would it be for hydronics and at what tempature? As long as we are maintaining a 20 degree deta T would supply and return tempature mater?

Thanks

Larry