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Hydronic loop length

Kyle_5 Member Posts: 6
I have a 40k btu bioler what is the max distance I can make a single loop?

also what is better direct vent or chimmey vent?


  • Weezbo
    Weezbo Member Posts: 6,232
    What size tubing?

    what size tapping's ? you could hook the 40000 heat source to some stout pex tubing and have a significantly zippier flow rate on that loop it really depends.

    then too, if my mind reading hats on crooked (i think it probably is...) you are probably referring to 1/2" loop length?

    then once again that too depends on what you can live with and for how long in the way of room temp. loop lengths of specific size pipe, heat loss, flow rates,emitters , resistance to head,on and on ...... about the easiest way to roll the idea of what i am saying is,if you look at the top of this page ,go to the library and look up I-pex. read a bit ...maybe you get an idea of the answer you are seeking if not , then maybe you could dial the question into one channel a bit closer and someone will help you sort this question that you have out.... just a bit closer ...
  • Brad White
    Brad White Member Posts: 2,398

    As Weezbo was suggesting, are we talking radiant? Baseboard? Piping in general? Flow rate and Delta-T?

    Any of those things is more dependent on the circulator you are using than on the boiler by far.

    PEX (if radiant) has general limitations of about 300 LF for 1/2" and 200 LF for 3/8". I would personally keep them shorter by another 33% but that is just me.

    If copper baseboard, I typically do not want more than 30 feet of element (15 MBH at 500 BTUH per LF) on a circuit. You can do more but it has to be compensated for by longer element at the ends. On the other hand, pipe the rooms in parallel and have the best of individual control.

    So many directions...

    As for direct versus chimney, I think most would agree that direct vent is more efficient. Firstly, it is a featured hallmark of a more efficient appliance to begin with. Secondly, it can take in it's own combustion air, often preheating it from the exhaust gasses if a coaxial system.

    With a chimney vent, even with a damper, you have a fairly large hole in your roof. Combustion air for the most part comes from the space which eventually has to come in from the outside in an uncontrolled fashion.
    "If you do not know the answer, say, "I do not know the answer", and you will be correct!"

    -Ernie White, my Dad
  • Weezbo
    Weezbo Member Posts: 6,232
    Thanks. Brad *~/:)

    my hats been a little disheveled recently, it comes from not having every answer politically correct, for the most part. :)
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