One Cold Radiator

MikeinNEPA

In short I have what appears to be an old 2 pipe steam system that was converted to hot water using the original radiators from when the home was constructed in 1925. My issue is that while generally the system works very well, the back bedroom radiator never seemed to work, I recently had to move a radiator in another room so I later took the time to bleed the entire system, including the cold back bedroom unit, but still no heat.

The unit did fill with water and I've checked a few times that there is no air in the system but it always stays cold. Could there be some kind of loop where hot water isn't circulating to it, but it is still filling with water? What should I be looking for in order to identify and correct the issue?

Thanks in advance.

Jamie Hall

Indeed there could be some kind of loop. It wouldn't be at all difficult for it to be plumbed in such a way that very little water would circulate through it -- which is what is needed -- although it would fill perfectly happily. In fact having that happen is a good deal more common than not, unless a good deal of care was taken in the conversion.

You need to trace out where the feed and return pipes to it tie into the rest of the system, and then -- this is the hard part -- figure out a way to persuade the water to circulate through it. Water is really lazy, and will take the easiest route, every time.

There isn't, by chance, a closed valve in there somewhere?

MikeinNEPA

There is a valve there but it is open, I'm wondering now what could we done to coax the water to pump into this radiator more effectively with out re-plumbing the whole system in the basement. Are there any type of secondary inline pumps that can be added to that run?

Jamie Hall

Depending on where you have valves, and what kind of valves they are, you might be able to reduce the flow to other radiators in the system and divert some of the flow to that misbehaving one. That's called balancing the system -- but it may not be possible, depending on how it's plumbed.

Can you post a diagram?

Paul48

Pictures would be great. Are you sure it's not a converted gravity system? Is there an old expansion tank in the attic, or the remnants of the plumbing from one? Is that radiator the most remote from the boiler?

MikeinNEPA

I'll try to get some photo's tonight, there is a large expansion take that is no longer in use, but it is above the boiler in the basement, there is also newer vertical expansion taken next to the boiler that is in use.

As for distance from the boiler its very possible that its the furthest but 2 other radiators are a very similar distance away, possibly, and I'll confirm tonight, this one is the furthest distance by length of pipe.

MikeinNEPA

Here are some photos of the heating system.

Steamhead

Looks like that was originally gravity hot-water- the supply and return pipes are the same size. A steam system would have return pipes noticeably smaller than the supply pipes.

Paul48

https://heatinghelp.com/systems-help-center/sizing-circulators-for-old-gravity-hot-water-heating-systems/

That looks to be a series 100 circulator. Use Steamhead's chart and see what your system should have for a circulator.

Jamie Hall

And not to be discouraging, balancing gravity hot water systems which are converted to pump can be tedious. However, the good news is that it can be done, and usually with the hardware which exists. One has to throttle down the radiators which are over enthusiastic, leaving the ones which are cooler or cold wide open. This is not a one turn and you're done process, but with patience one can get it very well balanced.

MikeinNEPA

Thanks Jaime Hall and Paul48, I'm going to try your method first Jamie just to see if I can do this fix on the cheap, if not I'll be trying to see if a larger circulator is in the cards.