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Buderus indirect water heater

I bought a new Buderus S-120 32g indirect water heater to replace my old indirect. After finishing the installation I found I had reversed the inlet and outlet to the heating coil. I found the old tank was reversed too. That's how I made the mistake. It doesn't seem to matter. Does anyone know if it does?

Thanks for your input.


  • meplumber
    meplumber Member Posts: 678
    Not a huge problem.

    The tappings are labeled in and out or supply return to take advantage of stratification.  The coldest water is at the bottom of the tank and comes into contact with the hottest water.  Under normal conditions you shouldn't notice any problems.  If it were a larger tank or a high demand setting then I would say fix it.  But a 32 gal tank in a normal residential setting, it should be fine. 
  • billtwocase
    billtwocase Member Posts: 2,385
    as Meplumber said

    and also how are you pumping thru that tank? Indirects like to be pumped into, not so much pulled thru with a circ on the return. 
  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    edited January 2011
    It depends?

    "Indirects like to be pumped into, not so much pulled thru with a circ on the return"

    It must depend on the boiler and the indirect. My installation instructions say to run supply into bottom of the indirect and pull from the top through a circulator into boiler return. Indirect is tank-within-a-tank design, so probably little pressure drop.

    With this design, I believe they want the hot going into the bottom to put maximum heat at the very bottom, perhaps to kill the bugs. Or maybe so convection causes flow up. I do not believe convection can be that important with a Taco 007-IFC pumping through there.
  • meplumber
    meplumber Member Posts: 678
    It depends on tank design.

    JDB, what you have is a Triangle Tube tank.  Probably with a Weil McLain Jacket.  These tanks first came out as Phase III tanks.  The physics of water flow are different than in a traditional coil tank.
  • Jim R.
    Jim R. Member Posts: 58
    I was just about to start the same thread!

    Our Buderus ST-200 (50gal) indirect tank was professionally installed 5 years ago. Day to day operation is fine, but the water is MUCH hotter than the aquastat setpoint. We keep it set at 100F and the faucet water temp is 140-160 degrees. The pressure relief value failed once becuase of the overheating. I verified that the circulator and aquastat are both working correctly.

    Today we ran out of hot water for the first time. I went to the heater room and it hit me-- the boiler water is circulated into the bottom of the coil. The instructions say it should go into the top! In this case, the thermostat sensor is much closer to the top of the coil which probably accounts for the overheating. I can't speak to the physics of water heating, but there has to be a reason why the thermostat is where it is.

    My guess is that the backwards flow of the heating coil is why I've had these problems. If it turns out this is the problem, is it something the installer should fix even though we're out of warranty. It's a clear cut installation error if so.

    Any thoughts would be appreciated. Thanks.
  • billtwocase
    billtwocase Member Posts: 2,385
    short draws

    will also help to increase water temp above the set point. Sometimes a strap on secured to the hot water out, in series, will help that situation. Pumping away is common practice. Can't see where that would be an issue with an indirect, where ones that I install call for that. There is no disadvantage to piping it that way
  • tim smith
    tim smith Member Posts: 2,498
    If it is piped wrong, yes he should fix it.

    Most indirects with tubular coils inside are counter flow heat exchangers that i have seen. Cold fresh water enters bottom and rises/flows upward and heating water enters at mid point of tank in coil and travels downward in opposite direction.
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