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Feeder/cutoff combination for large boilers

JoeyQ
JoeyQ Member Posts: 17
Hello all. I have a question about the installation of feeder/cutoff on steam boilers 5000 sq EDR and higher. I read that if the wrong location or piping is done on the installation of the feeder/cutoff, the water line will do strange unpredictable things. I have sourced photos for from "the lost art of steam heat" pg 206. My question is not with the entire concept of the cutoff/feeder but a single spot of confusion with the piping. The correct way of installing the feeder/cutoff is placing on its own equilizer column. The book says you pipe to a top portion of the boiler, but not a steam line. My only knowledge is through this book, and I'm aware that this piping is for larger applications. However isn't every tapping on the top of the boiler a steam carrying pipe. I'm aware that the header must be piped very carefully to dry the steam before it hits the main. The equilizer as I understand it is the (steam system ) pressure acting on the Hartford loop water seal, so water stays in the boiler. ( rather than run back up the end of the main) . Is the steam holding the water level a bit more stable inside of the feeder/cutoff device? I know the spot marked A is a low turbulent spot below the water line. This way the feeder doesn't come on unnecessary. I appreciate any insight thank you

Comments

  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,344
    Equalizer piping

    the water column that the controls are mounted on consists of a steam tapping on top of the boiler . It is connected to a steam space but not a steam flow line. You don't want any flow in that piping, just steam pressure. Flow could give the controls a false reading.

    Same with the lower water tapping. Tapped into the boiler. You couldn't for instance tap into a condensate return line, boiler feed pipe, etc and use it for the lower tapping.. You also couldn't pipe an indirect water heater using the water column as a return header (although I saw it done)
  • JoeyQ
    JoeyQ Member Posts: 17
    Steam flow line

    Ok the top of the boiler is steam space, that is what I need for the control to work. Is this static pressure alone to keep the water in that feeder in there ? When you say steam flow does that mean the feed for the main. After it is considered dry
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,344
    steam

    Wet or dry is not the issue here. A steam boiler has a normal water level  of about 1/2 a gage glass. The level varies within a safe range while the boiler is operating. Basically the boiler is considered safe to run if you can see the water level in the gage glass. If water is not visible it's not safe to run.etc..



    The water level will vary within the safe range while the boiler is operating depending on the load, condensate return rate etc.

    It's the job of the controls mounted on the boiler to keep the boiler operating within this safe range. To do that the water level controls need to be able to determine the present water level. The low water cut off(s), feed pump controls, and water feeder are sometimes mounted directly on the boiler itself or mounted on a water column. The water column is connected to the boiler steam space (top) and water space (bottom). So that the water level controls can work properly the water level in the water column must mimic the water level in the boiler.

    In order for this to happen they must be connected to the boiler directly and not to any piping with flow in it.

    Hope this helps



     
  • JoeyQ
    JoeyQ Member Posts: 17
    Thanks

    Ok that clears up piping mysteries. I know the root of my confusion is the automatic water feeder and the low water cut off. The device and how it operates internally are a bit foreign in concept to me. At the end of the day I understand why they were invented. I have never seen detailed photos or internal function explanation pictures. I appreciate all the insight that has been shared.
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,344
    LWCO / Feeder

    The important thing is that the piping for the control to sense the water level (1) tapping in the steam space and (1) tapping in the water space of the boiler is completely separated from the water feeder portion of the control.

    With the control mounted correctly to the boiler and at the right height to control the water level the city water connection  should be made to the inlet side of the water feed control.

    The city water should have a tee then a ball valve in  the  run of the tee as well as  a ball valve on the branch of the tee. One of these valves is connected to the water feeder. It should have a union in it so the feed valve can be changed while the boiler is running also a strainer to protect the feed valve from scale in the water line. The outlet from the feeder should connect into the condensate return to the boiler and not directly into the boiler itself if possible. This is so the condensate will help preheat the city water before it goes in the boiler. The feeder outlet should have a union, ball valve and a tee in that order. One of the tee connections is the feed to the boiler. I like to put a swing check valve in that line. The other tee connection connects to  the other ball valve previously installed for the bypass. This is to feed the boiler manually and this valve is normally closed.

    When the boiler is steaming and if their is not enough condensate returning to the boiler the water level drops and the float in the water feeder drops and mechanically starts to feed city water into the boiler to maintain the water line. If the feeder cannot supply enough water due to leaks in the boiler or system and the water level continues to drop the float will trip the electric switch mounted on the water feeder and shut down the burner.

    The feeder will continue to feed until the water level returns to normal raising the float and shutting off the city water. Weather the burner will restart depends on the type of switch mounted on the water feeder. Some are auto reset and some are manual reset depending on code requirements.