very Interesting steam problem

PEPPlumber

First off I came across an application that has old united states radiator convectors that no one has information in my area on.  I am looking for the EDR  for them for boiler sizing and adding a convector.  They are 63-1/2" wide and 23" tall.  The element inside is 4-1/2" tall and 6"  wide.  I have one supply house that says they are 66 Sq Ft EDR and another that says they are 55.8 Sq ft EDR.  Does anyone know the right size?

Here is the interesting part, the Mains are 2" and the returns are 1-1/4" and there are only air vents on the convectors.  The returns are always filled with air and are cold.  I am looking to install air vents on the returns near the last elbows to cure the problem, but if i do the calculation the additional footage of the piping will put me over the EDR of the boiler.   This is why i need the exact EDR of the existing convectors.   Thanks

Hitzkup

Piping edr

Your return piping does not effect the EDR rating of the boiler, you need to install the right size "main vents" before the end of the main.

PEPPlumber

Return piping

The return is included in the total EDR because it is not insulated and very long 50 FT.