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Thoughts on cascading boilers

tmachad2 Member Posts: 3
edited February 2022 in THE MAIN WALL
Just wondering if you think 2 cascading boilers would be worth an extra $ as opposed to just a single boiler, both connected to an indirect water tank.

It would be heating an indoor pool approx 350 sq ft and radiant floor approx 1600 sq ft and then also our hot water.

Is cascading 2 overkill or would there be benefits? Both are IBC VX150s 


  • Jamie Hall
    Jamie Hall Member Posts: 23,567
    Probably not. If one can handle the load. Those things claim a 6.5 to 1 turndown as is...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Zman
    Zman Member Posts: 7,589
    The 2 reasons to cascade are redundancy and better turndown ratios. Your radiant heat would probably benefit from the turndown ratio, the DHW and Pool are huge loads and should not shortcycle. The redundancy is up to you. A buffer tank on the radiant loop would take care of the cycling as well.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Matt_67
    Matt_67 Member Posts: 295
    Is it two 150’s vs a single 199? I guess if that’s the case you are mainly buying redundancy though it’s possible that the added turndown could be important depending on the size of each load. So then it’s a question of how well you can deal with the boiler being out. I can tell you we’ve had a few parts availability issues that have made me rethink redundancy.
  • hot_rod
    hot_rod Member Posts: 22,396
    So what is the total load? I'm guessing the radiant is under 40,000? The pool load? Indoor or outdoor?
    Seems 2- 150 are a lot of boiler?

    The unknown is how you heat the pool. If you want a fast warm up, it could easily suck all the btus from both.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • tmachad2
    tmachad2 Member Posts: 3
    The pool is indoor and we keep a cover on when not in use, so it should maintain its temperature fairly well. 
    I believe they calculated the total load to be around 200,000