EDR For 120 year old convectors?

AJPA

I'm trying to calculate the EDR for these wooden box convectors that are hanging in the basement. Is anyone here familiar with this type of convector? Its essentially a wooden box lined inside with galvanized sheet metal with what appears to be iron or steel pipes wrapped in coils of the same material. They are attached to ducts that go to registers on the first and second floors and used to draw air in from the outside in the old days. I can find no markings of any kind on them.

DanHolohan

https://heatinghelp.com/systems-help-center/indirect-hot-water-heating-q-and-a/

You can base max EDR for these on the size of the supply main. Scroll that article for details.