I recently added a new radiator to my hot water heat system via existing (once used by former owners) stubs on the 1" chase pipe around my basement. From what I gathered studying my system and the old pipes still hanging in the crawl space is the pipes feeding the system off of the chase are 1/2" (a mix between galvanized and black pipe). Although the supply stub is 3/4", the old pipe is 1/2" so there must have been a reducer that was removed when they took the system out. I used 1/2" PEX for simplicity when adding the new radiator to the old location. I reduced from the 3/4" supply tee to 1/2" and the return line was already set for 1/2". The return tee is a MonFlo tee. The problem I'm having is the flow from the chase is not traveling all the way through the new radiator through the 1/2" PEX. It has been 30 minutes + and the radiator valve is just now warming up.
Another thing to add: By the looks of the old system is was likely a 2-3 foot long, tall radiator and I am adding an 11' long Crane baseboard (cast iron). The run from the chase to the supply side isn't too much longer (3') and the run from the return to the chase is the same as the old system. There is a galvanized union close to the supply tee on the chase that could have been used to remove an old MonFlo tee when the system was changed but I would have no way of telling.
My thoughts and questions questions would be this:
1. The new radiator inlets are 3/4" so I should not have reduced going up to them in the first place.
2. 1/2" PEX ID is much smaller than 1/2 galvanized ID. Maybe I need to go to 3/4" pex on the supply side.
3. Go to 3/4 PEX on both sides and reduce it into the1/2" return tee.
4. Use the union on the chase to pull off the supply tee and add a MonFlo tee in its place to force more water to the radiator.
5. Is there a certain distance that the supply and return stubs need to be away from each other depending on the length of the radiator it is installing? Currently the two stubs are roughly 6' apart including a 90 bend. Again the new radiator is 11' long.