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Restaurant options for domestic.

Snowmelt Member Posts: 1,295
I service this one owner who has 3 steakhouses, he just recently inquired another restaurant.

He has an existing boiler with 6 zones valve. ( has 2 pumps in parallel, if one stops working he can isolate that pump and continue)
Piping and wiring looks like something from a taco training ( Webinar).

He also has a pretty decent flat plate HEX off the boiler for domestic water.
Also has a tm 50 from Takagi. To make the long story shorter the takagi and the HEX are by passing the storage tank and there using the storage tank water to mix the water down. ( it took me 1 1/2 hours to trace it in my head)
He wants to simplify everything. The Tankless is on its way out. I put a heat exchanger in for him to buy him time to think.
What do you think will get him more how water for money spent?

Option 1. Install two naviens and connect it properly to the storage tank. ( somehow use this flat plate hex exchanger in the equation since it exists.
Or maybe a navien boiler with an indirect feeding the storage tank at 150 degrees and mixing valve to 130 degree.
The other restaurant I put the navien in and he likes them .


  • Larry Weingarten
    Larry Weingarten Member Posts: 2,294
    Hi, If the boiler stays on year round, might that be a good heat source for the DHW?

    Yours, Larry
    HVACNUT Member Posts: 4,209
    Reverse indirect(s) off a separate boiler.
  • Snowmelt
    Snowmelt Member Posts: 1,295
    Hvac nut that’s what I was thinking, but what do you mean by reverse indirect? Also since they have a flat plate hex, can I maybe use that some how.

    Maybe use that with the existing boiler and storage tank , and boiler, then but a navien boiler only with an indirect?
  • Zman
    Zman Member Posts: 7,005
    edited February 2020
    Stop the madness! Start with the required storage and/or Btu's and do the math from there. Restaurant water requirements are often mandated by the health department. I would inquire there first. If you decide to use the existing boiler and a heat exchanger, you would have to consider the heating requirements of the building as well.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • mikeg2015
    mikeg2015 Member Posts: 1,183
    Tankless aren’t ideal Because the water temp requirements are so high and flow rates change constantly. But leak demands are manageable with storage. That’s my opinion at least. A boiler with indirects or reverse indirect (more flow, less pressure drop) is the way to go. Reverse indirect stores more total energy, which is the goal so you don’t need as big of a boiler or water temps as high, not storing lots of domestic water.

    Still need to Calculate peak Flow and the sustained flow. Normally bathrooms, and the wash sink and prep sinks are the bad load and you add the dishwasher Machine for peak loading.