no flow new radiator

Discussion in 'Boiler Forum' started by Eagle71, May 18, 2014.

  1. Eagle71

    Eagle71 New Member

    Aug 15, 2012
    Hello all. I recently replaced an old small cast iron radiator in my second floor bath with a runtal wall panel. They look very restrictive to flow so before I ordered it I did some crude calculating and figured the flow rate would be lower but doable. I bled the system and ran it for at least an hour and this thing just doesn't get warm at all. In fact the supply pipe for it in my dining room only gets hot a third of the way up. I removed it, opened the valves and checked for obstructions which there weren't any. All the other radiators in the house get hot, albeit at drastically different rates because of large iron piping that was replaced by the previous owner with 3/4" copper in some spots including the bath I'm working on. For instance, two of the second floor rads and one on the first floor get hot real fast while everything else is just getting warm. The boiler is operating at 15psi so I know that's good. I'm thinking the system needs some serious balancing to get this rad to work but I'm a bit apprehensive about doing it considering some of the valves look like they haven't been turned in decades. Anything else I should try before biting the bullet and repiping again to put traditional iron rad in? Thanks
  2. Dana

    Dana In the trades

    Jan 14, 2009
    You probably still have an air-bubble somewhere on that loop impeding flow. Air purging system that have been opened up for a radiator swap usually takes more than just a bit of bleeding at the radiator.
  3. Sponsor

    Sponsor Paid Advertisement

  4. BadgerBoilerMN

    BadgerBoilerMN Hydronic Heating Designer

    Mar 4, 2011
    hydronic heating designer/contractor
    We replace old cast iron radiators with steel wall panels like Runtal regularly. Since most were gravity to start with adding a radiator will-nilly with a 1/2" fitting fed by a 3/4"+ supply is wishful thinking. And then there is the thermal mass disparity and cold rooms even though you did the math and Runtal said the radiator was sized properly...

Share This Page