Could this be a Vacuum issue?

itzasean

SO I have a couple radiators that after running for a long time they stop heating up (on these cold days). I think I just realized that if I remove the vent on the rads it may have broke a vacuum and allowed the condensation (water) to get back to the boiler. Im thinking that since its been running so hard with this cold weather it got water logged. There was no spitting or water hammer. I have tried new vents through the years an nothing. Do you think thats possible that so much condensation piled up and there was a suction preventing the water to make its way back to the boiler but when I removed the vents it became free? (kind of like when you hold your finger on a straw it holds the drink until you let it go and it releases? Any info would be great. Thank You

Jamie Hall

Do they stop heating in the middle of a run of the boiler? That is, does the boiler keep running but the radiators cool off? If so, while it is highly unlikely, it is just possible that there is enough of a bad pitch on a runout or the inlet valve being partly closed that condensate could block the steam flow. Usually one would expect a water hammer problem -- or at least some gurgling noise. Otherwise, even if the vent is closed the radiator will keep heating so long as the boiler is running.

However, if this is a situation where the radiator simply does not start to heat or heats very poorly when the cycle starts -- the boiler starts -- again there may be condensate trapped somewhere, but it is also possible that the vent on the radiator is not reopening when the previous cycle stopped. That would usually be a damaged or otherwise failed vent. Try swapping vents with a known good radiator.

I might add that if the vent does close during a cycle, it won't reopen until the cycle ends.

I might add further that if the pressure is too high, that can damage a vent and cause it to fail closed.

Long Beach Ed

As Jamie says, watch your pressuretrol setting. Too much pressure on a long boiler cycle may exceed the "drop off" pressure of the vent, permitting it to remain closed even with the steam condensing.

More likely, as he says, the condensate's accumulating somewhere and stem flow isn't letting it return out of the radiator or runout.

itzasean

Well like last night the boiler was running non stop but at some point the heat just stopped and the rads cooled down. Not until I removed the vents did it start to heat up. Another question is how long should the steam take to heat all sections of the radiator. I am noticing that it takes a long time for the steam to reach the other side on a 7 section radiator. Boiler is set around 2lbs.
I have a feeling its some kind of water backup as its only on days like this and they all share the same run.

Jamie Hall

If it started to heat up when you removed the vent.. the vent was closed, no? However, if the boiler was running continuously during that time -- not cycling on and off -- boiler pressure (2 psi cutint? That's too high, by the way) should have been able to overcome any reasonable amount of pooled condensate. On the other hand, if the boiler cycled off on pressure -- which it probably did -- and the vent failed to reopen, the radiator would no longer heat. That's my first thought.

As to how long should it take for all sections of a radiator to heat? That would depend on how big the radiator is and how fast the vent is -- anywhere from a few minutes to easily 15 to 20 minutes from when the first section gets hot to when the last section does -- if in fact it ever does (it may not, on a shorter cycle).

Long Beach Ed

If you send a photo of the piping atop your boiler, we may be able to determine if a velocity issue is causing water to accumulate.

itzasean

Ill try and get a short video of my piping. Here is the Pressuretrol. Do these settings this good? The Steam Radiators are on the 2nd and 3rd floor of a 3 story 2 family home.

Jamie Hall

Pressuretrol settings look fine.

itzasean

https://www.youtube.com/watch?v=5eFXWd5MTNE

Here is a video of my piping the best i could do.