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Radiant Heating question

hemertwv
hemertwv Member Posts: 4
Hello;

Currently have a 5000 sqft home that has radiant installed 16 zones, with a boiler that provides domestic a radiant heat. The system is about 4 or 5 years old with heat transfer plate drawing heat from the boiler separating the two environments

The current boiler is a HTP phoenix 135K boiler and has no problem providing all heat required even in -40c weather, currently in the winter the boiler is set to 160 degrees

So here is the situation, last year the flame sensor went on the boiler and we were without heat for several days until I could get a new flame sensor. I have a spare now of both flame sensor and overheat, etc. but the problem still exists if something else goes wrong I have no secondary water heat source for both domestic and radiant.

And the question, I was contemplating after discussion with a local plumber to place an on demand condensing heater in line with the radiant heat transfer circuit directly following the phoenix boiler and set the on demand to 130 to 140, some tuning would be required. That would essentially mean assuming the radiant recirc is running and if the boiler is operating correctly the ON demand would not fire up, however if the boiler shuts down and as the boiler cools the water would run through the on demand and be heated as an interim measure.

Thoughts, tell me I'm crazy, I would even be open to bypassing the on demand until required but would prefer it to be automatic as much as possible.

Some of my concerns
1. I hear that using an on demand for radiant is not really recommended
2. Would having it run in this model impact the on demand if it was never fired up or not fired regularly


As a side note, I already have multiple pumps on each side of the radiant setup in an active/passive model, so I am trying to configure the house to be very reliable..

Thanks in advance.
Walter

Comments

  • Rich_49
    Rich_49 Member Posts: 2,589
    Could you post a few pictures so we could see how the Phoenix is configured now ?
    You didn't get what you didn't pay for and it will never be what you thought it would .
    Langans Plumbing & Heating LLC
    732-751-1560
    Serving most of New Jersey, Eastern Pa .
    Consultation, Design & Installation anywhere
    Rich McGrath 732-581-3833
  • STEVEusaPA
    STEVEusaPA Member Posts: 5,176
    If you're that paranoid about back up, just put another boiler in and use a control that cycles them.
    steve
    Ironman
  • hot_rod
    hot_rod Member Posts: 14,865
    If you want absolute redundancy, add an additional boiler, piped parallel so either could be enabled. Or buy a complete spare parts package for the Phoenix.

    I would definitely not try to use a tankless water heater, if that was the suggestion.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    Rich_49Steve MinnichIronman
  • Crissie
    Crissie Member Posts: 84
    hot_rod said:

    If you want absolute redundancy, add an additional boiler, piped parallel so either could be enabled. Or buy a complete spare parts package for the Phoenix.

    I would definitely not try to use a tankless water heater, if that was the suggestion.

    @Steve Minnich
  • Steve Minnich
    Steve Minnich Member Posts: 2,659
    Smart minds…
    Steve Minnich
    Minnich Hydronic Consulting & Design, LLC
    [email protected]
  • hemertwv
    hemertwv Member Posts: 4
    OK thanks kind of what I figured the response was going to be, thanks for the input, I will look for a secondary boiler as an option.
  • Ironman
    Ironman Member Posts: 6,437
    There are mod/cons that aren’t much more expensive than tankless and that would be the right tool for the job.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.