Steam Radiator Air Vents Won't Drain

Bobo

I hope someone can help me with this problem.

Last winter I insulated the mains and risers down in the cellar.  Ever since, the radiator air vents on my one-pipe steam system have been flooding.  It doesn't happen to every radiator every day but it's very common with a few of them. 

The scenario goes like this:  The boiler will fire up and a radiator will remain cold.  I remove the air vent, shake out a teaspoon or two of water, replace it, and everything is fine until the next time.  I've replaced the tongue-less Varivalves with Hoffman 1-As but the problem still persists.

Why won't they drain?  Does anybody have any idea what's going on?  Please help!

kcopp

sounds like a couple...

of things. Some how water is getting drawn up into the system. Could be poor piping at the boiler or Dirty water. Flush out the system and skim. Got pix?

kpc

JStar

...

Are the vents noisy, too?

SBoston

Wet Steam



Just a home owner here, but I have had the same problems that you have. Since it's happening to all your radiators it sounds like you have wet steam issues and condensation is building up in your radiator valves. This could be due to dirty water, improper piping or maybe to much pressure pushing condensation into your vent.

You could be having this issue now that you installed insulation because the steam is not condensing as much in the pipes before getting to the radiators.

I also noticed that having the correct radiator shutoff valve (for steam) makes a world of difference. I had a valve that said it was for steam and hot water on one of my radiators; it was the only radiator in the house that wooshed and flooded the vent. Once I changes the shutoff to a steam valve, the radiator worked perfectly.

Posting some pictures of your boiler and near boiler piping should spur some comments for the walls resident experts.

My 0.02

mel rowe

Winter pastime

Homeowner here also.  I used to have the same problem with vents clogging with condensate.  Even though I had revised my near-boiler piping, going from one riser  to two, I still had excessive steam velocity and wet steam because the boiler was way over sized.  I used to spend my winters going around removing rad vents and dumping water out, in order to get heat.  In desperation I decided to down fire my gas boiler by reducing the burners from 16 to 12 and adjustments were also made to maintain the right manifold pressure.  This got the steam velocity down to close to that recommended in Dan's book.  Since that change, I now have to find something to do with all the time I used to spend dumping water out of vents.  So, steam velocity could be part of your problem.  This would tie in with the suggestion that wet steam was previously being condensed in the mains, before you insulated.