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Indirect water heater

Dana Member Posts: 126
You don't.


  • chuck shaw
    chuck shaw Member Posts: 584
    Heat exchange

    When a cold start boiler gets a call from the indirect for heat, how do you keep the heat from going from the indirect back to the boiler, and therefore running out of hot water? I was helping a friend of mine today, and I asked him what he planed on doing. He didnt have an answer. He understood what I was saying, but didnt know how to stop it from happening.

    Normally I install a Buderus, with the Logomatic control, or a Munchkin, so I have not run into this issue.

    Any ideas would be helpful.

    Thanks in advance,


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  • chuck shaw
    chuck shaw Member Posts: 584

    there isnt a timer or a delay, that would allow the boiler to run for a couple of minutes before starting the circulator feeding the indirect?


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  • Big Ed
    Big Ed Member Posts: 1,117
    Reverse Aquastat

    You can hook up a reverse aquastat "B" to prevent the problem .I believe the 2107 has a setting to prevent the circulators from kicking on below a desired temperature for condensation .
  • Never really

    thought about it, but you're right; the warm water coming back from the indirect would pre-heat the boiler.

    The Viessmann Vitogas boilers have a thermostat that disables the pump until the boiler gets to 130° to prevent condensation. That feature could be used for more than one purpose.

    But come to think of it, it really doesn't take very long to heat the boiler water; there's only a few gallons in the indirect system.

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  • Steve Eayrs
    Steve Eayrs Member Posts: 424

    Chuck, Most cold start boiler I know of have their own recommended control statigy. Some supply and include whats needed, others just recommend something.
    EK is a good example of a non-condensing oil fired colds start boiler, and their controls don't open the dhw zone, or any others unless the boiler return temp. is warm enough.

    A triple aquastat (double acting aquastat) would work, as they canbe set up so the pump/zone doesn't kick on unless the temp. is above the low setting.

    Or as other recommended a normally closed aquastat that opens on temp. rise would work. I'm sure you could also give the dhw priority this way too.

    If this is a non-condensating type boiler, it gives you another reason for wanting to do this.


  • jerrygb46_4
    jerrygb46_4 Member Posts: 6
    reverse acting aquastat

    Seem like everybody hooked up too all this HI-TECH boola-boola and forget about the OLD L4006B (B)as in boiler).Just set it at 130 deg and Walla.
  • Tom M.
    Tom M. Member Posts: 237

    Amtrol's latest version of the smart control (the one with three buttons instead of just one) has a prepurge setting. the options are 0, 4, and 8 minutes. I believe the manual says that it is useful for cold starts and for larger boilers.

    Tom M.
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