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adding a radiant ( low temp ) on a cast iron boiler

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Snowmelt
Snowmelt Member Posts: 1,416
Have a job coming up, adding a small zone ( kitchen 6,000 BTU ) can i just run a zone off a small indirect. or should i use a boiler protector from Caleffi. I am not to concerned about short cycling as much as I should be . but i am thinking the indirect water heater would be an easy way to go.

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  • hot_rod
    hot_rod Member Posts: 22,270
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    Using the domestic water? What type of heat emitter?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Snowmelt
    Snowmelt Member Posts: 1,416
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    No just want to throw one of them small 30 gallon peerless just for the radiant floor. I’m using viega tub with plates and have a separate water heater for the domestic.
  • Zman
    Zman Member Posts: 7,579
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    Why not a Taco I series valve and a mixing loop.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • hot_rod
    hot_rod Member Posts: 22,270
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    Use the indirect as a buffer and HX? Set the indirect temperature at the desired SWT for the plate radiant? Not a bad idea.

    If the 6K load is a small % of the boiler output and the rest of the system is high temperature low mass, like fin tube, you may not need return protection.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Dave H_2
    Dave H_2 Member Posts: 556
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    Wait, I'm confused.

    Is there a boiler already there for heat to the rest of the house?

    If so, everyone is way over thinking it. Drop in a mix valve and a new circ and you should be all set.
    Dave H
    Zmannewagedawn
  • clammy
    clammy Member Posts: 3,113
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    Using a indirect for small radiant load is a excellent plan .I have used this set up in the past for small kitchen and baths and it works great and in my opinion 100 times better then just a mixing valve weather fixed or electronic .Having seen loads of systems just using a mixing valve all you had to was turn it on and even on design day watch your boiler short cycle .Another way which i have done where money is tight using a ranco etc ,mount probe on main loop and when ever any zone calls and comes up to temp the etc closes it contact and powers your radiant circ and away you go in which case a taco i series valve is a excellent choice you can still use a t stat but it will only be indoor hi temp limit to prevent over heating .I ve used this method on systems that are usually hi or mid temp systems w mod cons that lowest modulation is still over the radiant load and the boiler short cycles theres nothing more wastefull then a short cycling mod con .It really shines on mod cons that are properly sized and are used w outdoor reset .Makes those micro radiant load short cycling a thing of the past . For larger radiant system which are micro zone the use of a indirect is a very useful tool to use and have in your arsenal if your concerned about shortcycling .Kudos to snowmelt for looking out for his customer and forward thinking instead of saying that the short cycling is normal .Peace and good luck clammy
    R.A. Calmbacher L.L.C. HVAC
    NJ Master HVAC Lic.
    Mahwah, NJ
    Specializing in steam and hydronic heating
  • hot_rod
    hot_rod Member Posts: 22,270
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    Good advice Clammy, that 6K load on a design day, is a fraction of that most of the heating season, needs to be designed around.

    His approach is a "zoned" buffer tank, so to speak.

    To tie in just a mix valve to an existing baseboard loop would require that zone to be calling for the kitchen zone to work, unless you add a P/S loop or separator.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Snowmelt
    Snowmelt Member Posts: 1,416
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    Thanks guys, Dave it would short cycle and give to low of temp to boiler which I was trying to avoid.
  • Zman
    Zman Member Posts: 7,579
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    Snowmelt said:

    Thanks guys, Dave it would short cycle and give to low of temp to boiler which I was trying to avoid.

    With an I series valve, you can do outdoor reset and boiler condensate protection electronically.

    It is a good idea to look at short cycling. You do have a cast iron boiler which helps quite a bit. Why do you want to create 2 closed systems with an indirect? If you need buffer, just add a buffer tank.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • hot_rod
    hot_rod Member Posts: 22,270
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    Zman said:

    Snowmelt said:

    Thanks guys, Dave it would short cycle and give to low of temp to boiler which I was trying to avoid.

    With an I series valve, you can do outdoor reset and boiler condensate protection electronically.

    It is a good idea to look at short cycling. You do have a cast iron boiler which helps quite a bit. Why do you want to create 2 closed systems with an indirect? If you need buffer, just add a buffer tank.
    With the small indirect he can have it two temperatures, boiler temp and mixed down temperature. With a 15° differential on the aquastat it would provide a nice SWT to the radiant.

    Add reset to the boiler and both temperatures get reset.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Snowmelt
    Snowmelt Member Posts: 1,416
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    cost factor of a buffer tank and all the piping, I wanted to make it simple, I was going to cheat also, instead of 2 separate zone. ( bathroom and kitchen) I might just have one pump and if the kitchen or bathroom call for heat they both get heated, there close enough together, both tile floor and door to the bathroom is open ( unless doing a #2). I am thinking of a 30 gallon low boy from peerless, any suggestions on small indirect, I also have a taco fuel mizer but this boiler is older where i don't want to touch anything electronic, also customer doesn't trust any wall hung unit, he wants old school
  • hot_rod
    hot_rod Member Posts: 22,270
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    The smallest, least expensive tank. 30 gallon seems to be the smallest indirect, unless you go with an Everett or a marine style tank..
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Snowmelt
    Snowmelt Member Posts: 1,416
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    ill look at it later , who carries them I think my sales rep for that product is john serlerno
  • hot_rod
    hot_rod Member Posts: 22,270
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    not a lot of info on the TFI Everhot website as far as reps. Rathe does rep Turbo max and they have a 23 gallon reverse indirect that would work. I’d guess even a small indirect will run 800 bucks or more. Probably not the cheapest route.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Snowmelt
    Snowmelt Member Posts: 1,416
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    I am confortable with a Utica 30 gallon indirect, but the 22 gallon buffer tank isn’t out yet. Let me call a supply house next week.