Water not flowing through radiator

jonnyz

I have a hot water (two pipe) system that has a pump attached to the return lines.  I relocated a radiator, and ran new 3/4" piping to it. The supply line gets as hot as the other supply lines on this branch, but the water is not circulating through the radiator like the others.  The return line doesn't heat up very much at all, so the radiator doesn't give off much heat.  I don't know if this is a balancing issue and I the flow is not being pulled properly, or did I replace with the wrong valve?  Also there is a slight pitch back towards the radiator in one 2' section of the pipe.

I have purged the system of air, and there does not seem to be any obstructions in the boiler itself.  Any ideas how I can fix this?  Thank you for your help

Brad White

Can you post a diagram or photos?

We can provide the thousand words



Radiator elevation, system type (one or two pipe), former gravity system, etc.?



It would not be the first time that a radiator was piped from a supply line to a supply line or a return to a return, with little difference in pressure. I have found radiators on my old house, a MonoFlo system, where the tee was reversed and at best the radiator was tepid.  Just one of many possibilities.

jonnyz

Diagram

Ok here is a diagram to thes best of my knowlege. Please ask about any additional details you may need.  Thanks for any clues that may lead to getting this thing hot again.

Charlie from wmass

the pipe is too small

you now have a balancing issue. What size was the original pipe to and from the radiator?

Brad White

Agreed

Too small and you may have gravity working against you. The second floor, given the height and "gravity piping", has the path of least resistance. Your 3/4" run is not very interesting to lightly motivated water.

jonnyz

Originally

Originally it was 2-1/4" along the entireity of the header, then branched off to 1-1/4" inch pipe i think to the radiator.  That is what the 3/4" transitions to after the 90 to go to the second floor radiator. That radiator gets as hot as the others, but i suspect the elevation has something to do with that also.

There is another replaced radiator that is fed with 3/4" copper the whole length, and it gets hot also, which why i figured 3/4" would work

jonnyz

Zones

Thanks everybod for your input your help is very appreciated.  I still trying to find a solution just short of ripping out the radiator and running an electric in-wall heater.

The other c.i. radiator that is piped with 3/4" straight from the boiler seems to get nice and hot.  Is this considered a seperate zone?  Could I do the same for the cold c.i. radiator, or possible tie it into that zone? They are both in the same area of the house

Or could i add a circulator pump inline to the cold c.i. rad? 

Charlie from wmass

You could

add a circulator for that radiator. If it turned on when the zone called for heat it would help it get warmer. The question is if you do that what will it change. Why not run larger pipe to the radiator? 

Brad White

Adding a circulator

Adding a circulator "might" work, but you have to throttle it down until it imposes no residual pressure in the return. (wasteful, driving with the brakes on). I would strongly recommend increasing the pipe size.



I will give you an example of what can happen adding a circulator-

Student housing apartment complex near Boston, built in the 1970's. Some apartments at a lower level -near the pumps, I would add- had insufficient heat for reasons not determined at the time.  (It was a combination of a kinked pipe, some sludge perhaps and an air binding issue, best we could tell, but no matter).



Anyway, after some years of suffering this, someone got the idea to cut in a 007 into the lines feeding the colder units. This brought them heat. But it also created a larger problem. It raised the return pressure by some degree above what it was before the 007 was added. Even one ounce more than the incoming returns from other circuits will stop the flow. So when these few apartments called, the upper floors now suffered and were too cold. This somehow persisted for many more years and was deemed either acceptable or the management admitted defeat. Did not take long to figure out once we diagrammed it. Pumps gone, pipe replaced and re-routed, works fine now.



"Never before in the history of human comfort have so many been sacrificed for the comfort of so few."  Winston "Deadman" Churchill.

jonnyz

Thanks

Thanks Brad and Charlie, I was exploring options without repiping, primarily because I have all this 3/4" copper piping and valves that has to come out now. 

 I am DIY home owner obviously, what type of pipes are used today when you're talking about 2" and larger header pipes? Steel? Do they make pex in that size? What is reccomended/typical? I can run pipe no problem, but running in correctly is the challenge!  Thanks again you guys are a great resource