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hot water loop off steam boiler

hello to all

i have been in the trade for almost a decade but have only recently become exposed to the beauty of 'the lost art of steam heat'. why does the hot water loop need flow controls on supply and return? even when producing steam wont they both be at the same pressure and therefore have no flow. also, on one such loop there was a 3/4 inch pipe connecting the two flow controls, whats that for?

thanks for the help, michael
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Comments

  • Dan HolohanDan Holohan Posts: 11,944Moderator mod
    Flo-valves

    Are there to stop gravity circulation into the hot-water zone when it's not calling. It can migrate from either end, and that's why there are two.



    The line between the two is probably a bypass for blending, but I'm not sure which pic you're looking at.



    Thanks for reading me.
    Site Administrator

    dan@heatinghelp.com



























    Hug your kids.
    · ·
  • charliechicagocharliechicago Posts: 56Member
    its a nice suprise

    to get a response directly from you dan. but whats "gravity circulation"? and whats blending. like i said i have read the book but am new to much of the concepts.

    thanks, michael.
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  • Dan HolohanDan Holohan Posts: 11,944Moderator mod
    Here's a link

    that will give you a lot more info: http://bit.ly/WROR3q



    Gravity circulation is convection. The water in the steam boiler is very hot and it will rise from the boiler into the hot water zone by convection unless there's something in its way to stop it. The flow-control valves do just that.



    The blending is about the temperature of the water as well. When you're making steam, the temperature of the water in the boiler is about 215 degrees. If you were to pump that up into a hot water zone there's a good chance that the water will flash back into steam when the circulator shuts off. This isn't a pressurized system and that's why that can happen. By blending some of the water returning from the zone into the super-hot boiler water you can lower the supply temperature to the zone to 180 degrees, removing the possibility of steam flash when the circulator stops.



    That link will explain further. Good questions! Thanks.
    Site Administrator

    dan@heatinghelp.com



























    Hug your kids.
    · ·
  • charliechicagocharliechicago Posts: 56Member
    thanks

    thanks again dan, much appreciated.
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  • Dan HolohanDan Holohan Posts: 11,944Moderator mod
    Happy to help!

    Thanks for reading me. 
    Site Administrator

    dan@heatinghelp.com



























    Hug your kids.
    · ·
  • jonny88jonny88 Posts: 738Member ✭✭✭
    it works to..

    a contractor i work for needed a hot water coil piped in which was in the attic but customer had a steam boiler.if you follow the diagram as it is in the book it will work perfectly.i think it is in the how come book.you should read the theory behind it and how it works.i did an experiment when piping it in and put a heel tee with a bleeder valve on it.the second i opened it the boiler flooded.it was a great oppurtunity to get a grasp of how it works in real life,i then removed heel tee and replaced with an elbow.that pipe that joins the feed and return enables you to mix cooler return water with the hot supply water.with your gauges you can adjust the valve to where you need it.good luck
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  • charliechicagocharliechicago Posts: 56Member
    jonny 88

    Thanks for the response, much appreciated.

    You got me thinking with the example you gave, what does keep the water in the loop from pushing back into the boiler? What is a heel tee and why did that allow the water to flood the boiler?When you say gauge, you mean a temperature gauge?

    Thanks for your time and advice, Michael.
    · ·
  • charliechicagocharliechicago Posts: 56Member
    I lust finished

    reading link that dan included with his response, that answered my question about why the water stays up. But i still dont know what a heel tee is and why that caused boiler flooding.

    Thanks again, Michael
    · ·
  • jonny88jonny88 Posts: 738Member ✭✭✭
    heel tee

    in my supply house they actually call them baseboard tees.the middle port of the tee is called the bull and the other two ends are called the run.so on the run of the tee one end is 3/4 and the other end is 1/8 threaded or female.the bull of the tee is 3/4.you would screw a 1/8 air bleeder valve into the heel or run of the tee.in the system you are referring to if that tee was at the top of the system and you opened the air vent you would let atmospheric pressure into the system.that pressure would in turn push the water back into the boiler and the water level in the boiler would rise.the vent would work the opposite way in which you wanted it to.explanation in the book explains it properly
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  • charliechicagocharliechicago Posts: 56Member
    heel tee

    gotcha thanks again
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