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replacing BOILERS for domestic water

just ran into a 5 story apartment building that has 2 Raypak BOILERS for domestic water. no storage tanks. the returns are 2 inch and i guess the storage is in the larger piping.  They have been this way since 1986. the question is what is the best way to replace? They currently want to replace One unit. Raypak called it instant hot or something like that. They no longer offer the boiler models. Should the owner go with standard HW heaters and Storage tanks? or maybe a high effeciency condensing  HW heater like the Lochinvar SHIELD ? or start over and get a unit/ fixture count on the building and see if we need to do either of the above with a smaller HW heater. The current ones are 500,000 btu output nat gas boilers. They have another boiler in the mech room for heating.  


  • mempho
    mempho Member Posts: 4

    FYI - the boilers are pump mounted 1/4 hp BG's . there is a small BG pl pump on the return. The pumps mounted on the boilers supply the building with the domestic water. so new pump package will be needed.
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,853
    Do this...

    I've always found that RayPak's Sizing Guide is the best on the market. Using their guidelines for a storage tank/boiler combination, then use Turbomax reverse indirect(s) and the modcon boiler of your choice.

    The two pumps that were header mounted on the boiler were strictly for movement of water through the boilers, and not intended for circulation through the building, although I have seen them do that.

    Mount a small circulator on the circulation return to keep the hot water available on the far ends of the system.

    You will probably reduce their energy consumption by at least 25% for DHW in doing the conversion.


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  • Larry Weingarten
    Larry Weingarten Member Posts: 3,323

    Hello:  It would be good to get inside a handful of units to see what sort of fixtures and flow rates they have.  Getting rid of high flow fixtures first might allow you to downsize equipment.  Look for insulation on lines.  Check for an aquastat on the return and set it hot enough for a shower, (about 105 degrees).  Another way to get a good feel for it is to put a water meter on the cold supply to the heater/s and find out what the peak load is.

    Yours,  Larry
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