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Steam radiator air vent size question.

Nick11 Member Posts: 11
Great forum, learn so much about my steam system here.

Got a question about upsizing my radiator air vents to improve the efficiency of the whole system.

Boiler is in the back of the house basement. Have the main vent with a #1 air vent in the pipe at front of the basement before it goes up to the radiator above on the 1st floor.

Problem is that the radiators on the 2nd floor front of the house takes a while to heat up fully. Only half of the panels heats rapidly, and the rest takes a long time. The air vent on it are #C.

First question is, will there be an issue if I upsize the air vent. Not just one size up to #D, but maybe a #1. Will having a main vent size air vent on a radiator cause problems?

Second thing is that there is a straight pipe that goes through the 1st and 2nd floor bathroom in the middle of the house. This will heat up and has an air vent near the top of the pipe on the 2nd floor. What size should this air vent be? It currently has a #C. But thinking maybe it should be a #1 too? To help get air out of the system faster.



  • KC_Jones
    KC_Jones Member Posts: 5,529
    Sometimes it isn't about speeding up rads, but slowing others down. What size vents do you have on the other radiators in the house?

    How long are the mains? In my opinion an single #1 vent is only good for the shortest mains, say 10' or less. The main should be fully hot prior to any rad starting to heat, are you seeing this? If not, more main venting is in order. Once the main venting is squared away, the rads can be balanced.

    Also, a D and #1 main vent have the same capacity, so using a #1 vent isn't adding anything over the D.
    2014 Weil Mclain EG-40
    EcoSteam ES-20 Advanced Boiler Control
    Boiler pictures updated 2/21/15
  • Nick11
    Nick11 Member Posts: 11
    Main pipe is about 45 feet. The main vent is hot before the radiators.

    From your suggestion, looks like I might need to add more main air vent on the main pipe to increase efficency. I think I saw a post here about adding elbows and extentions on the current main pipe opening and just stacking a few #1 vents on it.

    2 radiators on the 1st floor back of the house are #5. 1 radiator in the middle of the 1st floor where thermosat is located is #4. This takes longest to heat up the whole radiator, I think thats how it suppose to be. The 2nd floor front of the house takes about the same time to heat fully as this #4 one. 5 radatiors on 2nd floor all with #C.
  • dopey27177
    dopey27177 Member Posts: 887
    First thing to consider is

    1. are the rooms cold when heat is supplied?
    2. Can you hang a thermometer in each room to see if the temps in all rooms are nearly the same?
    If one room is much hotter than the other rooms install a smaller vent valve in that radiator. see if that made a difference in the heat in the other rooms.

    Keep doing this until all the rooms are within 2 degrees of each other.
    The most important vent valve for the rads is the one in the room where the T stat is located, that vent should be the smallest vent valve in the house

  • Steamhead
    Steamhead Member Posts: 16,455
    @Nick11 , first thing I'd do is replace the Gorton #1 with a Gorton #2. This will get the steam TO the connections feeding the front radiators faster, which should solve your problem.
    All Steamed Up, Inc.
    Towson, MD, USA
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