What could prevent 3rd floor attic radiator from getting heat?

CoachBoilermaker

Was talking to my neighbor. He said in his old house he had this problem. He was never able to solve it. HVAC tech replaced radiator vent, and also installed a large vent on the pipe itself near the radiator, but that did not fix it.

Is there anything special about a 3rd floor radiator, steam not being able to travel that far up? What would be common culprits? Or just your standard blocked pipe, stuck closed vent, or imbalanced vent, etc.

ethicalpaul

it’s almost certainly that the supply pipe has settled with the house over decades and caused a sag or “trap” in the pipe that is holding water, which blocks the steam

All piping must be sloped such that the water (condensate) flows back to the boiler

clammy

possibly check pipe size to radiators edr ,check the supply valve and check that the valve and the washer are open and have not blocking the inlet. while valve is removed blow through the pipe if there resistance then the piping may have settled in which case see if the valve can be lifted if so raise the radiator by shimming it up and then see if see heats ,also make sure the radiator is pitched to the supply valve . i have also seen poorly piped near boiler piping making wet steam make it impossible to heat end of the main and 2 nd and 3 rd floor rads due to it being wet and folding back into condensate a;so lack of steam main being insulated all related

peace and good luck clammy

CoachBoilermaker

https://forum.heatinghelp.com/discussion/comment/1814073#Comment_1814073

What are main causes of wet steam?

CoachBoilermaker

https://forum.heatinghelp.com/discussion/comment/1814027#Comment_1814027

Risers go straight up to radiators, typically? So, the pipe that may not be sloped would be the main? But that does not explain why the other radiators work correctly

ethicalpaul

https://forum.heatinghelp.com/discussion/comment/1814152#Comment_1814152

Oily/dirty boiler water, bad near boiler piping. One indicator is if the water level drops rather dramatically at some point during the heating cycle.

https://forum.heatinghelp.com/discussion/comment/1814154#Comment_1814154

Well in my case, the whole riser settled creating a trap at the bottom of it, near the main.

But there is also typically a short horizontal section just before the radiator that can form a place for water to collect.

JUGHNE

Can you see that riser on the outside of the wall on the 2nd floor or is the pipe inside the wall?

If inside the wall it must come out between the 2nd and 3rd floors to go up to the rad.

There could be some horizontal pipe you can't see. Either up there or in the basement.

Long Beach Ed

Are you certain that the boiler has the capacity for that radiator? You may have to vent some of the lower ones slower to coax the capacity out of the boiler. Pitch or trapping of the pipe, as mentioned above is most likely.

AdmiralYoda

Simple things first. Make sure the valve isn't stuck shut. Even if you open it all the way if the valve itself is broken it might be permanently shut.

Take the vent off of the radiator when the boiler is running…is air coming out?

Follow the riser down to the basement. Do you have access to it anywhere between the third floor and basement? Does it get hot at any point on the riser? Does it switch to cold at some point?

clammy

Wet steam is produced by poor near piping ,under sized header ,single boiler riser used instead of both on larger boilers and muddy dirty boiler water does not help and system without pipe insulation does not help. Have you tried loosening the supply valve nut from the radiator and see if the pipe will lift ,if it does then see if you can raise it a 1/2 to 1 inch if so the shim the radiator up to the new height and reconnect and see how it works . If there is a sag this may all you the need for the horizontal piping to regain some pitch . The other opt is to use a air compressor and blow down the riser and then flush using a hose and water . You may just as other stated just have a pile of rust blogging the pipe . Its all old stuff so treat it w some TLC not to create a big problem.

peace and good luck clammy