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Strange happenings

which is another reason to move that circ to after the air separator/expansion tank conection, pumping away from this point. It helps flush air back to the separator.

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  • Bob Forand
    Bob Forand Member Posts: 305
    Strange happenings.

    One of my friends, who is a contractor, replaced a boiler. He swapped an old WM pin style for a Viessmann VR133. There happens to be one loop which is a cottage that has 1/2" pex run underground to it. It is approx 20K heatloss and is a ZV application. The problem is that the cottage heated up okay with the WM, and now it is not heating as well. He made one change in regards to the location of the circ. It was located at the return tapping of the boiler, and he moved it to the supply tapping of the boiler, before the expansion tank. Well we are having one of those friendly disagreements. I say that he really did not change the location of the pump and that the output should not have been effected. He says, he believes it has something to do with the movement of the pump. Could it be that he is now pushing through the ZV now instead of pulling through it ? Any ideas ??
  • bruce_21
    bruce_21 Member Posts: 241

    Is the new boiler operating at the same temperature as the old one? Did he add anything else to the piping run, elbows, valves? 20K btu is a lot for 1/2 inch pipe. What sort of emitter is in the cottage?
  • Paul Pollets
    Paul Pollets Member Posts: 3,656

    Good point...only 12K Btu's can transfer from 1/2" piping. Add for friction loss if the zone is 50ft+ from the boiler. That doesn't leave much left.

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  • Brad White
    Brad White Member Posts: 2,398
    What is the delta-T?

    Granted, 1/2-inch anything is not too impressive, but the capacity limitation is one of flow. If this were a microtube system, this could be delivering hotter water with a 30, 40, 50 or 60 degree delta-T, not just 20.

    It may be say 1.2 GPM but that can translated into 36,000 BTUH with the right persuasion.

    Mind you, I have no idea what the system distribution is, but it is still worth keeping delta-T in mind.

    One has to wonder though, for the expense of burying 50 feet of piping, was even the 5/8" size a little much for the budget?

    "If you do not know the answer, say, "I do not know the answer", and you will be correct!"

    -Ernie White, my Dad
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