Upstairs radiators not getting hot

jeepwm69

My house was built by my grandparents right after WWII (started in 47, finished in 48). House had radiators that we are using for heat, and I can't get the upstairs radiators to get warm.

So let's start with what I know.

Single pipe system, which has one hot water pipe (copper) going throughout the house, with lines coming off of it going to and from radiators. I honestly expected to see separate lines but apparently this is common.

Downstairs radiators all get hot without issue. Boiler has about 20PSI.

Upstairs had water line in, valve is open. Two radiators are connected to each other, sitting side by side. Air has been bled out of them.

Expansion tank is metal and in the basement rafters above the boiler.

The two lines going to the upstair radiators are at the very end of the system, about 6-8 feet from the circulation pump. I suspect this might be part of the problem.

Radiators are ice cold. I went to the basement and felt the lines, and the inlet line is warm, other line is not.

The lines run through a closet on the ground floor. Both lines are cold in the closet.

Yesterday I went upstairs and started bleeding water. After I bled out a couple of gallons I checked the inlet on the first radiator and it was hot. I bled out more water and the top pipe running between the radiators was warm, but the pipe going between radiators at the bottom was still cold. This tells me the inlet is clear and will allow hot water in.

This leads me to believe one of the following might be the issue.

A) This circuit is at the end of the system so there's not enough pressure to force water through the circuit. I don't THINK this is the issue as the pump would be pulling water and is close to the pipes going to these radiators.

The return line going from radiators back to main line is clogged

C) The way these two radiators are hooked together is somehow not allowing flow

The upstairs bedroom has been uninhabited until recently when my teenaged daughter decided to move up there. According to my mom (who grew up in the house) the upstairs radiators never worked very well at all.

My grandfather paneled and finished the upstairs bedroom some time in the 50's, doing the work himself, so I'm wondering if the way he has the radiators hooked together might be creating the issue.

Anyone have any ideas? I'd like to get heat up there so my kid isn't running electric heaters that might be a fire hazard.

To explain pictures
First is inlet going into radiators
Second is how the two radiators are connected to one another (top to top, bottom to bottom). It's hard to see the top connection, but there is a pipe connecting the two rads at the top just like the one visible at the bottom.
Third shows the lines coming off the main line. Closest is return line, further away (wrapped in foam) is inlet line. Flow direction is towards camera
Fourth shows the pump, with line coming into top of the pump from where pic three was taken. About 4-5 feet of line between rad lines and the elbow doing down into the pump.

Alan Welch

D. The return line is frozen.

jeepwm69

Frozen as in clogged?

Alan Welch

Water usually won't clog a pipe but ice will. In the really cold weather frozen pipes are much more common.

jeepwm69

Gotcha. Pipes run through the middle of the ground floor, which is heated. No chance there's ice in the lines or radiators.

Jellis

Do you know if the radiators ever produced heat in the current setup? Or is this a new issue that has started recently?

Alan Welch

I didn't read the full post either at first. Said it never heated well

jeepwm69

I found another post here that seemed to indicate that the radiators are properly connected together, and in that case the supply and return lines were too small to allow flow. Would it be possible that is the the case here? I think the lines are 3/4" currently. https://forum.heatinghelp.com/discussion/148871/reducing-coupling-on-two-upstairs-radiators-at-end-of-run-causing-problems/p2

Other than that I don't know what it could be. With the bleeder open hot water is allowed into the radiators, so short of lines that are too small or a blocked off return line is there any other explanation?

Alan Welch

I ight be wrong , but I think having them connected top and bottom is wrong, I think it more likely to work if the tops weren't connected

jeepwm69

That's one thing I wondered about. I've never seen two connected together to see what the proper way is to do it.

jeepwm69

I closed off the downstairs radiators last night, and the line going upstairs did get hot further along than it did before, but still not enough to push hot water all the way into the radiators.

I did find the lines going upstairs are 1/2", while the lines going to the ground floor radiators are 3/4". Could this be my problem?

Alan Welch

Doubtful the pipe size is the problem, more likely the diverter tees are facing the wrong way.

jeepwm69

And there are supposed to be arrows/ markings on the T's showing the proper orientation, correct?

Alan Welch

Yes, some type of markings. A picture showing the two tees should help.

Alan Welch

Also, search on this site for the explanation of diverter tees- Q&A. It might help you find what the problem is

jeepwm69

Looked at the T's yesterday, and I looked at the diverter tee Q&A, which was very interesting. Thank you for posting that.

This is the tee on the return line going to the upstairs radiator that isn't getting hot. Long run of 1/2" pipe going to the radiator



This is the tee on the regurn line of the radiator on the ground floor in the kitchen. Short run of 3/4" pipe



Only markings I see are the patent numbers

https://patents.google.com/patent/US1663271

From what I saw on the Q&A though, given the length of the line shouldn't the line size be larger than the ground floor radiators that have much shorter runs?

Alan Welch

Is the arrow on both tees for those radiators going in the same direction?

jeepwm69

Yes. Both tees are on the radiator return lines, and both are pointing towards the pump, which is pulling from this section of the line.

Alan Welch

i think that is the problem, right now both tees are trying to force the water up, I think the second tee should be reversed, or the first replaced with a normal tee. hopefully others more knowledgeable than me will chime in if i''m giving you bad advice.

billtang

The pipes to your two floors are in parallel or in tandem? If in parallel, the water may just go through the first floor pipes without going to the upstairs. If in tandem, I don't see why one is fine and the other is cold.

jeepwm69

I think I might have given info in a way that isn't making things clear. The two tee's pictured are on two different radiators. I put pictures of both to show an example of the tees going to the ground floor radiators (3/4 outlet). There is only one diverter tee on each radiator line, and that is on the return line. The tee on the supply line of each circuit is a standard tee (not a diverter tee). I apologize for not making that clear above.

Billtang, the pipes are in parallel, which is why I think the problem might be undersized pipes going to the upstairs. Longer distance to travel and the lines are 1/2" as opposed to 3/4" going the shorter distance to the ground floor units.

Alan Welch

Before changing the pipe size I would try eliminating the upper connection between the 2 radiators. Should be fairly simple, take the pressure off the system and remove the union and cap or plug what remains. See no reason for it to be there.

jeepwm69

Won't that trap air in the top of the first radiator? The bleeder is on the 2nd radiator.

Alan Welch

Yes,it will. Thought that there were bleeders on both.

Alan Welch

I think if you put a valve between the tees that you could partially close, and a purge setup on the return from the radiators to get out any air that might be trapped, you could get some flow.

SuperJ

Might be a good idea to install a air vent with a hydroscopic cap in the upstairs radiators, since the upstairs loop will be an air trap. The diverter tee's won't likely develop enough pressure difference to force any air down the return pipe that makes it's way up. Air can be slowly re-absorbed but if you have a big air trap that likely won't happen.

You could cut in a ball valve and drain on the return line. Open the drain and close the ball valve and see if you can drain hot water thru to the basement from system pressure. Or if you have a valve on the supply side of the radiator upstairs, close it so when you bleed it will makeup thru the return pipe and see if the pipe/rad gets hot as you bleed air/water out.

If you close the makeup water valve, does the system hold at 20psi for a couple days? If you are making up water, you will be making up air too.

Assuming you return line is good, you could do something to increase the pressure drop between the tees in the bypass, assuming you prove the return line works:
-Replace the supply tee with a second diverter tee
-add a full port ball valve to the bypass so you can throttle it to balance flow
-Repipe the upstairs in parallel with the downstairs, or split your loop in half.
-Move the supply tee further ahead in the primary loop so to increase the pressure between the tee's
-Pump the upstairs as a separate zone with an appropriately sized dedicated pump
-Repipe everything as parallel home run, this will introduce a bunch of other issues as your system should've been designed initially to compensate for cooler water on circuits that pull off further down the primary loop as it got cooled by returns.
-Change you pumping arrangement to pump away from the boiler (and expansion tank).
-Put a properly sized for your flow microbubble air separator between the pump and boiler after you move the pump.

https://www.google.com/search?q=hygroscopic+air+vent+cap&oq=hydroscopic+airvent+&aqs=chrome.2.69i57j0l3.5753j1j7&sourceid=chrome&ie=UTF-8

jeepwm69

SuperJ said:

Might be a good idea to install a air vent with a hydroscopic cap in the upstairs radiators, since the upstairs loop will be an air trap. The diverter tee's won't likely develop enough pressure difference to force any air down the return pipe that makes it's way up. Air can be slowly re-absorbed but if you have a big air trap that likely won't happen.

You could cut in a ball valve and drain on the return line. Open the drain and close the ball valve and see if you can drain hot water thru to the basement from system pressure. Or if you have a valve on the supply side of the radiator upstairs, close it so when you bleed it will makeup thru the return pipe and see if the pipe/rad gets hot as you bleed air/water out.

If you close the makeup water valve, does the system hold at 20psi for a couple days? If you are making up water, you will be making up air too.

Assuming you return line is good, you could do something to increase the pressure drop between the tees in the bypass, assuming you prove the return line works:
-Replace the supply tee with a second diverter tee
-add a full port ball valve to the bypass so you can throttle it to balance flow
-Repipe the upstairs in parallel with the downstairs, or split your loop in half.
-Move the supply tee further ahead in the primary loop so to increase the pressure between the tee's
-Pump the upstairs as a separate zone with an appropriately sized dedicated pump
-Repipe everything as parallel home run, this will introduce a bunch of other issues as your system should've been designed initially to compensate for cooler water on circuits that pull off further down the primary loop as it got cooled by returns.
-Change you pumping arrangement to pump away from the boiler (and expansion tank).
-Put a properly sized for your flow microbubble air separator between the pump and boiler after you move the pump.

https://www.google.com/search?q=hygroscopic+air+vent+cap&oq=hydroscopic+airvent+&aqs=chrome.2.69i57j0l3.5753j1j7&sourceid=chrome&ie=UTF-8

Interestingly enough I had to see an auto vent like that on a separate system in the house a few months ago. That one is copper line run through a tile floor in what used to be a garage, and is now a den. My grandfather put it in during the 50's. Lines are hooked to a water heater with a small circulation pump which is wired to a thermostat. When I replaced the water heater I had air trapped in the lines, and the old auto vent had clogged up with minerals from decades of venting. It's a closed system so the the old water heater lasted about 35 years. Heated floors are NICE.

So back to the radiators upstairs, When I went to see if I could bleed air I got only water, no air at all.

There is an inlet valve on the radiator inlet, so your idea of closing that, then seeing if I can still bleed water out using the return pipe. That would allow me to see if the return line is blocked somehow.

If I get flow through the return line, I'd say I'll have to either enlarge the lines or add a 2nd circulation pump to the lines going upstairs.

Dad has radiators in his house too, so he hoards old US made Bell and Gossett stuff. Might see if he has a pump I could plumb into the lines going upstairs.

Thanks for all of the replies. I love my radiators and learning how they work is definitely interesting.

jeepwm69

What about putting a ball valve between the tees on the main line in the basement? By partially closing it could I force water through the upstairs circuit?

SuperJ

jeepwm69 said:

What about putting a ball valve between the tees on the main line in the basement? By partially closing it could I force water through the upstairs circuit?

Yes, there are two parallel flow paths, one is thru the upstairs rads, but it's restrictive due to different factors (pipe size, length, air blockage, etc), the other path is the bypass between the supply and return tee's in the basement. The only restriction on the basement bypass path is the diverter tee on the return. So if you throttle the bypass it will force more flow thru the upstairs rads. I admit this is a bit of hack, and the long time diverter tee guys around here will probably not like the idea.

I said full port ball valve, so if you have it wide open it won't be messing with your system's balance.

SuperJ

jeepwm69 said:

If I get flow through the return line, I'd say I'll have to either enlarge the lines or add a 2nd circulation pump to the lines going upstairs.

Dad has radiators in his house too, so he hoards old US made Bell and Gossett stuff. Might see if he has a pump I could plumb into the lines going upstairs.

Thanks for all of the replies. I love my radiators and learning how they work is definitely interesting.

A modern wet rotor circulator isn't that expensive, and many are made in the USA too.
I would use a pump that works with modern pump flanges if you are going to go to the effort of cutting one in and repiping.

SuperTech

After reading this thread I agree with the advice that Super J gave. I would try the full port ball valve idea first, it's obvious a water flow problem and the original installation isn't adequate. I would avoid installing a circulator pump just for a couple radiators, especially an old B&G.

Perhaps installing another monoflo tee on the opposite side will help provide the pressure drop needed for proper flow.

Let us know if you find a solution, I hope you get it going without too much trouble.

SuperJ

To be clear the balancing ball valve would go in the bypass pipe between the supply and return tees. And it would be throttled the minimum amount required to get the upstairs rads hot.

This might have been confused with my other suggestion to add a isolation valve and a drain to the upstairs return line to allow the upstairs circuit to be purged from the basement.

jeepwm69

Yeah, I'm good at coming up with hacks that kinda work. Ha. While a valve in the main line would theoretically work, I don't want to screw up the flow to the rest of the house to try to heat the one upstairs bedroom

I need to try to close the valve on the radiator inlet and see if I can bleed them before I jump into anything else. It's been in the 60-70's here the last few days so boiler has been inactive.

Supposed to drop to 25 tonight when a cold front comes through so I'll let the system heat up and see what happens with a closed inlet valve and the bleeder open.

Thanks again for the help!

jeepwm69

Last night I shut the valve off on the inlet and opened the bleeder. I did get water, but it was more of a dribble than anything. I "bled" it for several minutes, then went to the basement and found the line was still cold to the touch.

I'm not sure how much pressure I should expect to find on the return line, but I expected more then I got.

Couple of pics of the lines going to the upstairs radiator. The shorter run is the inlet, the longer one is the return.

At this point I'm thinking the best route might be to replace the lines with at least 3/4". That would solve either a partially blocked line OR an issue caused by undersized lines, right?

jeepwm69

The pipe with the insulation is the supply line. You can see the return line coming off of the main line to the right.

The 2nd pic is the return line at eye level. As you can see it makes a 90 degree turn to the side, then another 90 degree turn to go up through the floor, through a closet on the ground floor, and then to the radiator upstairs.

SuperJ

Sounds like you found the problem, I would start at the tee, check for blockages, and replace as much pipe as possible.
I think 1/2" is likely sufficient, but you could upsize to 3/4".
You may want to have an extra diverter tee on hand just in case.

Are there any valves on the return line?

The dribble you got may have just been from the supply side, it's often difficult to get old valves to fully close.

jeepwm69

Looks like if I'm going to go with 3/4" line I'll have to replace the tees in the line. Both are 1/2 output.

No valves on the return line.

I concur that the dribble might well be seeping from the supply side.

Looks like I'm going to get through the winter using an electric space heater up there, and drain the system this summer and see if I can replumb it.

The water supply valve for the boiler is dripping anyway, so I need to remove it and install a ball valve in its place. Will do it all with the system drained once it warms up.

DZoro

Don't know if this has been mentioned but, I prefer with a monoflow system to bleed air with the system pump off. Have 2 people keep system pressure just below pressure relief of 30 psi. Then start pump, stop pump, bleed, start, stop..... keep repeating....
Monoflows are super critical with air, had systems that literally takes days/ weeks. But its all about the air and it don't take much.
D