Looking to identify pipes on hot water radiator

midi

Hello, I've been reading for a while and now have a question myself. Have a hot water radiator on the 3rd floor that has an extra pipe coming out the side that has been terminated (see picture). I'm wondering what that is for, if it's been a previous connection to the radiator? Any ideas? It's next to the radiator so it seems a strange placement.



Background is that I have another radiator on that floor that's not heating up at all, just bleeding cold water and I'm trying to identify the piping, so I can make some guesses on what the issues are.

Thanks much in advance!

Steamhead

It probably went to the original expansion tank, which would have been mounted on the wall in that room, or in a closet, or the attic.

nicholas bonham-carter

Most likely your cold radiator problem results from piping problems near the boiler, or in an incorrectly setup/located thermostat.—NBC

midi

Thanks, expansion tank would make sense here. 

The whole house is on one Thermostat with one zone. So yeah probably some kind of piping problem. It’s strange that the one “old” radiator on that floor is hot and the newer fin tube is cold. 

Other options I’m suspecting are a clogged valve, or air lock somewhere between the floors. But not sure how to test that, since I can’t really flush just this zone since it’s all connected. Any recommendations on what to try? Besides opening up the walls and checking the pipes?

motoguy128

Probably air locked. Are there any bleeders or air vents on the fin tube? Also if the piping wasn’t size or distributed properly when modified, it’s easy to get some preferential flows. The original hot water system might have been gravity (no circulator) or use a very weak circulator and the piping is oversized for hte flow. The new fin tube will be much smaller and cause an imbalance when mixed.

On a gravity system a small radiator might Still be 1” pipe, whereas on a modern copper or fin tube system A while room might be on 3/4”.

mattmia2

A ci radiator can hold quite a bit of aor before it will affect flow. Baseboard just needs a relatively small pocket of air to prevent flow.

If it is a flow balance issue you could make the pump run continuously and see if some heat gets to the fin tube eventually.

midi

Yeah that’s what I’ve heard about baseboard vs the big old ones. 

There’s a bleeder on the fin tube, but that only bleeds cold water. Tried to bleed it for quite a while but no luck for warm water. It’s hard though without really knowing how the pipes go. I suspect the baseboard is connected to the new bathroom they put underneath, but not sure what exactly they did with the pipes there. 

mattmia2

If air isn't coming out, bleeding it more isn't going to help

could try increasing the fill pressure temporarily and see if that shrinks and dissolves the air enough to get it circulating

midi

I brought it up to 25psi (from 20), so it’s already running pretty high. Hasn’t made a difference though. The one baseboard remains stone cold while all others (baseboard and regular) are boiling hot.