Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

Steam Radiator Help

New to the site, so please be conservative with the technical terms.

My four second floor radiators no longer become completely hot. Generally the last two fins at the steam vent end are cold to the touch. This is a single pipe system

Prior to every heating system I blow down the boiler by turning the thermostat all the way up, bringing the boiler to steam and evacuating the air by removing all the radiator steam vents (first floor and second) until I see steam venting from the radiator.  This season, I only saw steam escaping from the radiators on the first floor, and the second radiators got moderately warm but did not steam.  Now that the weather is cooler and in order to increase the room temperature I have removed the steam vents from 3 of the 4 second floor radiators. Room temperatures have improved but radiators are still only partially warm. No problems occurring with the first floor radiators.

Does anyone have any suggestions or resources as to what the problem may be?

Thank you


  • Open vent test

    Be careful in removing the air vents on the radiators, as steam can burn skin, and remove wallpaper in a very short time.

    As it is you have already performed the open vent test, showing the radiator problem to be in the supply rather than the vents.

    Look in the basement and see if the radiators which are cold are all fed from a different steam main pipe from the hotter ones. If that is the case, then look for a sag in that main line which may be trapping water, and as a result air, preventing the steam from getting to the radiators.

    You would benefit from having some of the steam books for sale at the shop here which will enable you to understand your system better, and do some of the maintenance your self.

    Tell us what your pressure is, and post some pictures of the boiler and radiators.--NBC
  • Ilkstmht
    Ilkstmht Member Posts: 13
    Open Vent Test

    Open vent test


    Thank for your help.

    The cold radiators are located on both of the steam mains, meaning two

    of the radiators are located on the main that services radiators in the

    front of the house and two of the radiators are located on the main that

    services the rear of the house. The only commonality I see so far is the second floor location of the problem radiators.

    After my initial post, I checked the cut-in pressure and it seemed to be set at 2psi. (However, I forgot to read the dial and only looked at the control box setting. Subsequently I changed the setting to close to .5)

     I will take a look at the steam books offers as  I have read some of the on-line information. I will post some pictures soon if it helps foster a solution.

    Thanks once again.

  • Importance of a good gauge

    If the looped "pigtail" under the pressuretrol becomes plugged, then an accurate gauge will show you that something is wrong with the pressure by showing no pressure.

    What else may be in common with the cold rads-type of vent?

    Something must have changed, and caused the upstairs radiators to not fill with steam.

    Some vents stop working at elevated pressures, and therefore allow the air to block the steam.-- NBC
  • Ilkstmht
    Ilkstmht Member Posts: 13
    Radiator doesn't heat with Vent


    My upstairs radiator seems to heat only with the air vent off. With the air vent off, i hear the air "puffing" constantly but the radiator does get hot. When I put the air vent on the radiator is cool. I have tried different vents with the same results. Any suggestions.

  • Pipedope_2
    Pipedope_2 Member Posts: 14

    Do you have a working gauge? If so, at what pressure are you running?
  • Pipedope_2
    Pipedope_2 Member Posts: 14
    edited January 2014