Moving / resizing heating pipes

[brainbone]

I'm in the process (radiators are draining as I type this) of removing the larger, low hanging, huge, iron heating pipes from the basement, then relocating and replacing them (with copper?) to gain more headroom for a basement remodel.

Right now, the feed from the boiler (Weil-mclain HE-5) immediately reduces to 1" copper, splits to a 3/4" zone feeding two kick space heaters, and a 1" zone that then splits to 2 3/4" copper lines that increase to (~3" ?) iron pipes (the pipes I'm removing) that feed the front and back of the house (3 cast iron radiators on 1st floor, and 3 on 2nd). Exact opposite for the return. I'll be adding a 3rd zone for an indirect water heater and a 4th for baseboard radiators in the basement during this process.

Any general words of wisdom out there you would like to share?

I'm familiar with running copper, so its my first choice, but would entertain pex if I can be convinced otherwise.

How about pipe sizing?

 

[hj]

heat

I am surprised that a 3/4" line can provide enough flow to heat those radiators.

 

[Sponsor]

 

[brainbone]

That's the way it was installed when I purchased the house.

I added the 3/4 line to the 2 kick space heaters, and they seemed to work fine with that, but I always wondered if the 3/4 lines, each eventually feeding 3 large cast iron radiators, was large enough. The radiators do get hot though.