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Air venting problems

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I recently purchased a home with a two pipe steam heating system and have been having some issues with it. Many of the radiators were not heating properly and upon inspection I realized that only one main vent was working. I could find only two air vents in the basement. One was faulty and releasing steam, that one being on the main steam line and the other had been removed and capped which was on the dry return just before the boiler. I got two Hoffman 75 vents and went to work installing them. The main line vent went in with no issues but the one on the dry return began spitting water out of it as soon as the system reached 2 psi. I removed the vent and fired up the boiler to see if steam was coming through on the dry return and it began blowing water and steam everywhere covering my basement in rusty water. Does this mean that I have one or more steam traps that are faulty and allowing steam through on the dry return? My second question is why would only about half of my radiators have steam traps? I did find 3 traps piped into the dry return in the basement. Is it normal for some radiators to be piped to a main trap in the basement while others have their own individual traps?

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  • Jamie Hall
    Jamie Hall Member Posts: 23,454
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    First off -- 2 psi is too much. It is entirely possible that at that pressure you are backing boiler water out into that dry return, hence the lovely fountain. Your system should be set to cutout no higher than1.5 psi, and cut back in at 0.5psi. With a pressuretrol, that's about as low as you can go.

    Second, unless this is a vapour system (in which case even 1.5 psi is too high, but that's for the next go around here), every radiator has to have its own trap and discharge to the dry return -- with one exception: rarely you may see a radiator which discharges to a wet return only, in which there has to be a vent on the return line. But that's rare.

    You may well have failed traps. That's not that uncommon.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • cybersid
    cybersid Member Posts: 3
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    Thank you for your advice Jamie. I understand that 2 psi is to much and my plan is to install a vaporstat and low pressure gauge. I was trying to fix the air venting problem first because I thought the lack of venting was causing the higher pressure. That and i think my pressuretrol is shot because it is set to .5 and 1.5. For the few minutes the new vent was on the dry return the pressure dropped down to almost the correct level but then I got the "lovely fountain" effect. Is 1/2 psi over really enough to blow water back out of the boiler through the return line? The boiler did lose about half of its water when I got the fountain. I just assumed it was a siphon effect from there being steam pressure in the dry return and then bursting out of the vent. If it is just a pressure issue thatll make my life much easier. If I fix the pressure and reinstall the vent and the dry return lines still get really hot does that mean it is the traps too? My previous post about some radiators not having traps was incorrect. Some of them were just put in below the floor and in the basement.
  • Jamie Hall
    Jamie Hall Member Posts: 23,454
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    Half a psi probably shouldn't cause the fountain. Each pound will raise the water level in the line going to the dry return about 28 inches. There may be another problem I'm not seeing just at the moment.

    However, that said, if you fis the pressure and reinstall the vent and the dry return still gets hot -- indeed you may have one or more failed traps. Not that uncommon...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    cybersid
  • cybersid
    cybersid Member Posts: 3
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    Thanks Jamie and thank you for your prompt responses. I will start with the vaporstat and go from there. Hopefully more questions won't follow.