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Boiler Feed Question

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RayWohlfarth
RayWohlfarth Member Posts: 1,552
Greetings
I was reviewing the piping for a boiler feed unit and saw that the manufacturer suggests an overflow loop if the condensate is hotter than 200 Degrees F. I have been staring at it and trying to figure out why they need it. Any ideas on why that is required would be appreciated. I was thinking it was to keep the condensate from flashing but they also show a full size vent. Thanks
Ray Wohlfarth
Boiler Lessons

Comments

  • GBart
    GBart Member Posts: 746
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    I think it's to protect the pump and to protect against flash and as a secondary vent.
  • RayWohlfarth
    RayWohlfarth Member Posts: 1,552
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    Thanks @GBart
    Ray Wohlfarth
    Boiler Lessons
  • GBart
    GBart Member Posts: 746
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    Like I said ..."I think.." :D
  • Steamhead
    Steamhead Member Posts: 17,000
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    Cooling leg?
    All Steamed Up, Inc.
    Towson, MD, USA
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  • Mike_Sheppard
    Mike_Sheppard Member Posts: 696
    edited September 2018
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    I was thinking it was to stop vapor from escaping, because at that temp you might have some vapor left over that would go out of the vent. A loop seal like that would hold it back to a certain point rather than letting it be wasted out the vent, but at the same time wouldn’t allow the tank to over-pressurize to more than the weight of the water in the loop. But the drawing in the picture shows the loop in addition to the vent.

    Maybe it’s just to stop vapor from escaping into the space in which the tank is installed.


    EDIT: Now that I look at it again, I’m pretty sure that’s what it’s for. To stop vapor from the high temp water from escaping into the room. The loop would stop that but still allow the overflow to function as designed.
    Never stop learning.
  • RayWohlfarth
    RayWohlfarth Member Posts: 1,552
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    @Steamhead I was thinking that as well.
    @Mike_Sheppard I thought that but am not sure because there is another vent on the tank which is full size and it does not say to vent it to the outside. I am leaning to a cooling leg but still not sure. Blowdown coolers on boilers are designed to reduce the discharge temp down to 140 to go down the drain. Don't know if the cooling leg can lower it that far.
    Thanks
    Ray Wohlfarth
    Boiler Lessons
  • DanHolohan
    DanHolohan Member, Moderator, Administrator Posts: 16,565
    edited September 2018
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    Thinking back to my Hoffman/Domestic days, they used to put a rubber plug in that hole where the overflow loop is now. It's there to relieve pressure should someone plug the air vent. That usually happens when the condensate gets too close to the flash point because of bad traps or high system pressure. The receiver isn't rated to withstand pressure. They can and will explode. We used to get those reports. The loop is safer than a rubber plug. I hope that helps. Great question, Ray. Thanks for asking it.
    Retired and loving it.
  • RayWohlfarth
    RayWohlfarth Member Posts: 1,552
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    Thanks @DanHolohan I appreciate it
    Ray Wohlfarth
    Boiler Lessons
  • DanHolohan
    DanHolohan Member, Moderator, Administrator Posts: 16,565
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    And I appreciate you.
    Retired and loving it.
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,829
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    so the water make up float come off and causes the mu water to overfill the tank and the loose float blocks the overflow you still have a vent to relieve pressure
  • Mike_Sheppard
    Mike_Sheppard Member Posts: 696
    edited September 2018
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    I did some digging. Apparently some manufacturers refer to it as “Devon’s Loop”. It is used to prevent flash steam/vapor from discharging into the boiler room for safety reasons, which could happen at higher temperatures like that.

    Now you’ve got me curious. I will call B&G tomorrow to find out! I’ve come across some higher temperature tanks that could benefit from this.
    Never stop learning.
  • DanHolohan
    DanHolohan Member, Moderator, Administrator Posts: 16,565
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    At the time, the guys there talked to me about explosion protection.
    Retired and loving it.
  • JUGHNE
    JUGHNE Member Posts: 11,102
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    Being how we are all on board about feeder pump piping, I will somewhat hijack this with an install I have coming up.
    Existing Sterlco feeder pump to be replace by new same model.
    This new 4128-GMX, 30 gal, 1/3 hp, has 2 1/2" inlet with 2" overflow inlet on the side near the top. The center of each seem to be about the same height off the floor. There is a 2" vent on the top of tank.

    What I want to do is by-pass part of the discharge back into the tank. I was thinking of putting a 3/4" line into the 2" vent that would have the 1" vent line going up to the ceiling.
    This single pump supplies 2 Burnham IN 8's. There is an electric solenoid on each boiler.
    Even if both boilers are calling the inlet flow is so much that the 1-1.5 PSI steam pressure is wiped out and has to recover.
    (this is a rare case of undersized boilers installed)
    The inlets are now throttled down by 2 3/4"ball valves but that is not enough.

    By piping the bypass into the top 2" vent fitting I hope to not return too much water that it will back up into the inlet or go out the overflow next to it.

    The piping diagram for this shows a tee cut into the vent pipe as an overflow. No trap shown.
  • RayWohlfarth
    RayWohlfarth Member Posts: 1,552
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    @Mike_Sheppard and @DanHolohan @EBEBRATT-Ed So that is there to be sure there is always an air pocket on the top of the tank so the system can vent air? Hmm makes sense.I was in a boiler room where they had steam pouring out of the vent and went into the electrical panel and shorted a bunch of stuff. Wasnt pretty
    @JUGHNE If it were mine, I would probably send it back to the pipe where condensate returns. Most manufacturers are pretty tough about the vent being full size.
    Ray Wohlfarth
    Boiler Lessons
  • DanHolohan
    DanHolohan Member, Moderator, Administrator Posts: 16,565
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    I agree with Ray.
    Retired and loving it.
  • Mike_Sheppard
    Mike_Sheppard Member Posts: 696
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    It’s amazing how something that seems simple can serve many different purposes. Having the second overflow can make sure there’s always an air pocket, stop steam from escaping into the room, serve as main vent in the even the float falls off and plugs up the top vent, etc.

    Hard not to admire some of the thought that has been put into things. Or the failures in products that have lead to these features today.
    Never stop learning.
  • RayWohlfarth
    RayWohlfarth Member Posts: 1,552
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    @Mike_Sheppard Good point. I think the steam can still get out the main vent also unless of course we put labels on the pipe telling the steam where to go. LOL
    Ray Wohlfarth
    Boiler Lessons
  • Mike_Sheppard
    Mike_Sheppard Member Posts: 696
    edited September 2018
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    I was thinking some more, the vent pipe doesn’t have to be vented outside does it? So you’re right, that steam would still vent into the room. I was picturing it vented outside in my head. So if that were the case then yeah that blows my theory out the window about the seal stopping steam from entering the room. Would make sense if the vent went to outside.

    What I meant was, if the vent was vented outside the steam would go out the vent, and the seal on the overflow would stop it from entering the room.

    I do know the plumbing code says no steam shall discharge to the drainage system, and the manual instructs the overflow to run to the drain. Maybe that has something to did with it.

    Didn’t have time to call B&G
    Never stop learning.
  • GBart
    GBart Member Posts: 746
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  • RayWohlfarth
    RayWohlfarth Member Posts: 1,552
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    @Mike_Sheppard It will be something I will be looking into
    Thanks
    @GBart That is scary
    Ray Wohlfarth
    Boiler Lessons
  • JohnNY
    JohnNY Member Posts: 3,244
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    Hey @RayWohlfarth, look at what I ran into on Friday:


    Contact John "JohnNY" Cataneo, NYC Master Plumber, Lic 1784
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  • RayWohlfarth
    RayWohlfarth Member Posts: 1,552
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    @JohnNY Thanks my friend. Thinking it may be piped incorrectly The vent is plugged I appreciate it
    Ray Wohlfarth
    Boiler Lessons