Radiator Not Heating

Mike T., Swampeast MO

Not all ball valves are "full port" and will offer significantly more restriction to flow than those that are truly full port.

Dan_15

I posted a question a few weeks ago about a Burnham radiant radiator no longer heating after repiping work was done. The consensus on the Wall was that the new piping could possibly have introduced a pressure differential issue, which is prohibiting proper flow through the radiator. I have bled all the radiators to no avail--I cannot find any trapped air. The strange thing is that I am able to force some flow of hot water by bleeding gallons of water through the top right bleed valve. But the radiator will not flow by itself. I'll try and post a picture of the visible piping tonight.

The plumber who did the repiping is suggesting to increase the system pressure at the fill valve. To be honest with you, the radiator heated fine at the current pressure before any work was done. Should I be concerned about doing damage to the system by increasing the pressure, or do you think this sounds like a reasonable thing to try. Thanks, Dan

Brad White_9

It is not pressure at work

but differential pressure across the supply and return lines.

Increasing the pressure is like further blowing up a balloon. It adds pressure but without a differential you have no flow.

Can you take a pressure reading across the radiator? Might the piping be coming of the same line? (Two supply or two return connections?)

You have to have a differential pressure; see if you can measure it. Pete's Plugs fit into 1/4" tappings and maybe the air vent tapping might have a role to play. But across the piping, measure that if you can.

Dan_15

Thanks, I tend to agree that increasing pressure is not a good idea. Something is preventing flow, but I dont have the tools to be able to check pressure differential. I wonder if the supply and return were inadvertently reversed. The supply inlet (bottom left) feels very hot to the touch while the return (bottom right) is stone cold. I wonder if the supply were mistakenly tapped into the system return, if it would still be hot to the touch.

Brad White_9

If you can accurately check

the temperatures at the supply and at the radiator, you may have an answer. To the hand and without simultaneous comparison one hand to the other, hot feels hot..

Timco

May be totally air bound, or air bound in a supply / return pipe. I have had this happen. If you have a 2-pipe system, turn off the other rads on that zone, except the troubled one. It forces the flow through the troubled or bound rad, getting things moving. Then be sure to bleed the rad. Reversing the supply/return will not stop a properly piped rad from heating. Is the rad valve open? That would do what you are describing if it were closed. If possible, PURGE the troubled zone well....

Tim

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Dan_15

Just wanted to update this post....plumber came and removed the ball valve he had put on the supply for the purpose of "throttling" the radiator's output. That seems to have cured the flow problem. For my own learning, is there any reason why a ball valve could possibly have restricted flow, other than being obviously defective? Could a simple ball valve mess with the pressure differential? Anyway, its fixed, and thanks to all who responded for your suggestions. Dan

Brad White_125

Ball Valve Restriction

Interesting situation... Ball valves typically have very low relative pressure drops, equivalent to between one and five feet of pipe at that size. "Full port ball valves" are at the low end of that scale and "standard port" valves are reduced by one pipe size roughly so tend toward higher equivalent pipe lengths of course.

The only way I can see a fully open ball valve (any ball valve) causing such a restriction is if all of the other radiators had generously sized runouts and hence a shorter apparent path. For example a converted gravity system with one inch runouts versus a newly connected radiator with the equivalent of a half-inch orifice... Still I would be surprised if you got absolutely no flow.. I would expect at least some.



Oh- thanks for the update!

Brad

Dan_15

Actually, Brad, your astute observation describes my system precisely! It is converted gravity with 1 inch runouts on all the radiators, except that the two radiators in the remodeled bathrooms have 1/2" runouts. These were the two radiators with the newly fitted ball valves. They always had 1/2" runouts, but never had the ball valves before this remodel.

Interestingly, the guest bath worked fine even with the ball valve. What would happened was that the master bath would remain stone cold while the guest bath heated up. Once the guest bath became blazing hot, the master bath would get a bit tepid. I could never get it to work better than that. So, it was getting some flow through the ball valve like you describe, but not enough with the ball valve in place. Why did it stay tepid while the other one got blazing hot? Maybe because it is last in the series, or maybe the run is a bit longer.

In any event I am glad it works now.
Dan

Brad White_125

Glad to be prescient, Dan

I suspect that the Guest Bath is on a higher floor? Or at least has less resistance than the Master Bath as you stated. If on a higher floor, as in all gravity systems without restriction, the higher the elevation the higher the flow potential. Top floors heat first...Stack effect...

The other trouble you have is that your situation, if you have to have it, should have been reversed. Master Bath hot, Guest Bath cold. Otherwise they will never leave...

Cheers!

Brad