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Boiler Bypass

World Plumber
World Plumber Member Posts: 389
in THE MAIN WALL
Bypass location on hot water boiler. Is it best before or after the pump? I've seen drawings both ways. My thought is you can get better mix control after the pump. Do you agree?

Comments

  • Mark Eatherton
    Mark Eatherton Member Posts: 5,853
    It depends....

    are you trying to protect the boiler, or the loads?



    If the boiler, use an ESBE Thermic bypass valve (Danfoss owned) and eliminate guessing and having to adjust at "Design" conditions. Locate it on the return back to the boiler, and as long as that point is above the flue gas condensation point, good system flow will occur. If below, most of the flow is shunted from the system to the boiler until the boiler is warm enough to release BTU's.



    If for the system, a 3 way down stream of the boiler, with the pump pumping away from the 3 way offers best protection.



    If you use a condensing boiler, you don't have to worry about ANY of that stuff, but I suspect you knew that, and the decision is budget driven, not efficiency driven.



    ME
    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • Greg Maxwell
    Greg Maxwell Member Posts: 212
    Thermic valve

    I agree, that a thermic valve is a great choice, but it is very cost prohibitive. This is a great question. Where would you locate the old fashioned ball valve style bypass Mark?
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,853
    edited August 2011
    As follows...

    If you are protecting the boiler, the pump should be pumping away from the boiler, and the bypass branch would be down stream of the pump, connected back to the return. Siggy has calculations in his book about adjusting it, but I've never seen one work as designed. A half hearted effort at best that causes a feeling of an uncontrollable slipping clutch. When you put the petal to the metal, it just seems to sit there and spin.



    If protecting the system, my previous statement about a 3 way configuration applies.



    How expensive do you think the ESBE Thermic is? I'm thinking it is less that a couple a hun bucks installed, and is cheap insurance if constant condensing is a possibility. The alternatives are to employ a variable speed injection system, and that REALLY gets expensive (pumpS, controls, etc)



    Having seen the insides of boiler WITH an ESBE versus WITHOUT an ESBE, I can tell you that they DO work. The insides of the boiler were virtually spotless.



    ME
    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
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