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Kool Rod
Kool Rod Member Posts: 175
Hi- Thanks for the info. Since you didn't answer my questions as to what type of steam system you have and about the main vents I'm assuming that you might have some confusion on this so I'll go over it. Basically there are two types (with many variations) of steam systems: "One Pipe" and "Two Pipe". "One Pipe" means that the radiators have just a single pipe connected to them and "Two Pipe" means the radiators have two pipes connected to them. While these systems can have a lot of common problems there are also problems that are unique to each system type so it is important to know the type of system we are dealing with.

Main vents - The path of steam from the boiler to the radiators starts from the boiler and goes through the mains (large pipes) and then branches off on riser pipes to each individual radiator, where the steam enters the radiator and condenses back to water giving up the heat it has brought with it. This heats the radiator which in turn heats the room. The mains are filled with air so for the steam to be able to get into the mains, there must be vents that allow the air to escape from the pipe. If the air can't escape, the steam can't get into the mains. When you trace out the path from the boiler along each main, the main vent are usually found after the tee where the last radiator on that main branches off. A main vent is usually attached to the main by a short length of pipe and looks like either a can of cat food on its side or a large silver bullet pointing upward. Main vents will allow the air to escape but shut when steam reaches them. One of the first things you need to do is locate the main vent on each individual main and determine if they are working. If they are working the pipe at where they are attached will be hot. (Be careful - they can be very hot!) If just warm or cold they maybe just partially working or not working at all and need to be replaced. Once we are sure that steam is getting to the branches of each radiator we can then deal with how to get it into each individual radiator.

You need to trace out and diagram each main as to it route and where each radiator branches off and the location of the main vent. After the main vent, the pipe continues back to the boiler on what is called the "return" so trace this also.

While you need to trace the whole system. Let's just start with the problem mains and find the vent(s). There maybe just one vent or there maybe a vent at the end of each branch. On a two story look for any steam pipes leading up to the attic as there maybe a vent up there at the end of the steam line.

All that I have mentioned is explained far better in Dan's books which include diagrams and different variations of systems that maybe found. Again I highly recommend that you buy them. They very quickly pay for themselves many times over. I'd also consider finding a real "steam pro" and having them look at your system. There are lots of excellent ones on this board. Steam is a very simple system though not many people both homeowners and heating professionals understand it.

Let us know what you find out about the vents and we can go from there.

- Rod


  • Therold Jules
    Therold Jules Member Posts: 3

    4 apartment building sharing one steam oil boiler. Every radiator works fine except 3 in apartments 1 and 3. The furthermost bedroom on apartment 1 is not working to full capacity and the equivalent bedroom on the third does not recieve steam at all. While apartment 1 kitchen is working full blast, it's equivalent kitchen on the third floor does not recieve any steam. I have disconnect the radiators and drained any accumulated water but even with the radiator off there is no steam coming out. Any idea what I have to do ? Thanks.

  • mark ransley
    mark ransley Member Posts: 155

    Im no pro but had issues that floors were redone and radiators were put back in level, you should not have water in radiators they should be angled to drain back. In one apt I actualy lifted the pipe in the floor as it settled and was holding water. Id say check pipe-radiator angle and check-replace return air vents. I had one room 55f it could not heat, now I can vent it to 84 if I want. It could be also balancing the radiators that you just loose to much to other apts that have leaking vents. Gorton 4-D I use to balance everything. Its a lot of work.
  • Kool Rod
    Kool Rod Member Posts: 175

    Hi - Need to ask you a few questions to clarify your situation/system.

    From what I can gather this is a 4 unit apartment building, four stories high? One apartment per floor? Is it a one pipe steam system? How many mains are coming out of the boiler and which mains have the "problem" radiators? Have you located the main vent on each main? Give us a bit more information and then we can go from there. If you give your location you might be able to find a steam pro on this board who is near you and could help you out.

    If you don't have them already I'd highly recommend Dan's steam books. (See "A Steamy Deal" at the bottom of this page) They're easy reading and crammed full of facts steam and how to trouble shoot steam systems and are written so the average homeowner or professional can understand them.
    There a "must" for anyone with a steam heat system and will save you a lot of money and hassle.

    - Rod
  • Therold Jules
    Therold Jules Member Posts: 3

    Thanks Rod.It is a 2 stories four apartment building, 2 on each side. There are 2 mains leaving the boiler that are branched into 4 for the four apartments.The problem radiators are the ones in the apartments on the left side of the building and the innermost bedrooms on both the first and second floors.
  • Supply House Rick
    Supply House Rick Member Posts: 1,404

    if you remove a radiator, and no steam comes out, then there must be a blockage either in the supply, in the case of 1-pipe steam; or in the return in a 2-pipe system. in some cases where there are traps for 2-pipe steam, they will not operate at overly high pressures, but that would not explain the absence of steam from the supply. could you have a horizontal which feeds that rad which has subsided, and become waterbound. if there is such a pipe below check it with a good level to make sure it slopes towards the boiler. your eye may be fooled whereas the level knows all sees all. a copy of "the lost art of steam heating" will give you more information on this subject.--nbc
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