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Critique my boiler/DHW plan

Fitty Member Posts: 6
I'm in the process of installing a Buderus G124X II and 40 gallon Buderus indirect water heater (with 2107 Logomatic) to replace the old boiler in a gravity feed system. The old boiler was centrally located and had a separate supply and return going to two sides of the house (east and west as labeled on the drawing). I'm using 1 1/4" copper to tie into the existing 2" cast iron and will bring that back to the boiler on both sides as shown in the schematic I've drawn. I've been reading on here and trying to learn as much as possible about correct piping flow (not bull heading, etc. (what I was originally planning to do before reading around)).

I'm interested in any feedback I can get to improve piping, efficiency or correct any mistakes I've made. Also I didn't show it, but I will be adding a hot water recirc loop off the indirect to the second floor bathroom.


  • Al Letellier_9
    Al Letellier_9 Member Posts: 929
    gravity conversion

    Not bad but it will run like any old heating system. Why not make that a primary loop, secondary in the boiler, go to constant circ which will keep the rads warm all the time the system is heating, and take off the indirect from the secondary piping. You will stop the primary pump on a call for DHW. With the 2107, you can get an add on module to do the job. Your local rep or tech support should be able to help you. This is how we do all our gravity conversions and the customers love it. Along with outdoor reset and constant circ, you would never know the system had been converted. You would still experience the comfort of warm radiators and even heating.

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  • Fitty
    Fitty Member Posts: 6
    RE: Gravity conversion

    I don't think I'm following you with the P/S circuit design. I am planning to run the radiator circulator as a constant flow with ODR through the 2107 and the DHW will be set as the priority in the 2107. Are you saying to put the radiators on the primary with constant circulation and the DHW on the secondary? I think that would take 3 circulators on the primary (one for the primary loop and 1 for each side of the house) and then another for the DHW?

  • Ted_9
    Ted_9 Member Posts: 1,718

    Well, the R2107 has boiler protection. Your design shouldn't be a problem unless there is a huge amount of cold water in the system. It may be a good idea to use the BFU room sensor too.
  • Fitty
    Fitty Member Posts: 6

    Do you think I need a boiler bypass?
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