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Water Heater or Boiler

giceman1337giceman1337 Member Posts: 41
edited January 9 in Radiant Heating
What method do you use for heating your hydronic radiant heat and domestic hot water. Please comment as to why you chose that method (pro/con).

Water Heater or Boiler 6 votes

Boiler for Hydronic + Water Heater for Domestic
33%
WillieJmikeg2015 2 votes
Combo Boiler for Hydronic and Domestic
50%
hot rodMark EathertonHVACguyinME 3 votes
Combo Water Heater w/ Tank for Hydronic and Domestic
16%
Rich 1 vote
Combo Tankless Water Heater for Hydronic and Domestic
0%
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Comments

  • SteveSteve Member Posts: 517
    Boiler with indirect
    But depends on the customers needs and budget
  • giceman1337giceman1337 Member Posts: 41
    I meant for the "Combo Boiler for Hydronic and Domestic" to represent that. I wasn't sure the exact wording to use. Also can't figure out how to edit the poll.
  • GordyGordy Member Posts: 7,586
    Depends on the demands, and wants of the owner. Some nice combos with greater tdrs that can manage lower heating loads better, and have the extra output for DHW.

    I’d favor indirect, and boiler. Nice to have a reserve of hot water on hand if the boiler goes down.

    A lot depends on water quality with combis on the domestic side hx. Maintenance , and longevity can be an issue.

    Tankless has same concerns.

    With indirect very high storage temps can decrease longevity. However you can leverage storage capacity with higher tank temps, and having a tempering valve for the fixtures.

    What’s your situation?
  • giceman1337giceman1337 Member Posts: 41
    I will have about 1200ft^2 in basement (likely Warmboard or Roth panels) and 1200ft^2 underfloor on main level with aluminum spreaders. I have forced air heating as well, so the radiant heat is to "take the chill out" of the floor. Rough estimate I made was <70K BTUs/hr for radiant.

    The domestic needs are 3 bathrooms with showers. 2 adults and 2 kids.

    Right now we have a crappy electric water heater that is 14 years old. Looking to replace water heater, at same time as installing radiant heating, so I'm wondering what's the best fit.
  • GordyGordy Member Posts: 7,586
    You would want to run the radiant with forced staged to supplement the radiant IF needed, not both together.

    Deffinetly do a heat loss calculation room by room before you start your project. It is the basis for creating the radiant heating design. Is this new construction? 70 k sounds high.

    There is one advantage to a stand alone gas tank style water heater. That is if boiler goes down you will still have hot water. Made a lot less efficiently however.
  • giceman1337giceman1337 Member Posts: 41
    I was wondering how to configure to the 2 thermostats. I have a thermostat on the main level for the forced air. I will have a thermostat in the basement for radiant heat. I may have an additional thermostat on the main level for the radiant heat. I also have a 2nd story which only heats with forced air. I do have a connected "smart home" hub system where I could wirelessly connect all the devices and provide some of the controls within the hub.

    The 70K estimate was high. I was calculating 20 BTU/ft^2 * 2400 ft^2 = 48K BTU. Then I added in radiant back loss for the basement slab ~10% loss (2 BTU/ft^2) = 2.4KBTU. Then I just fudged the numbers to a much higher value. What I also computed, which I believe is adequate is 15 BTU/ft^2.

    So I am probably closer to 40K - 50K BTU/hr for the 2400ft^2 of heating.
  • IronmanIronman Member Posts: 3,989
    @giceman1337
    If you're trying to use a poll to determine the best choice for your situation, you're going about it all wrong. This is a scientific trade that requires dealing with facts - facts that can be somewhat different for each job site. Those facts are NOT derived from an opinion poll.

    A heat loss calculation, actual job site conditions, viable methods of design and installation, and how much $$ is reasonably budgeted are all things that must be factored.

    As far as personal experience and opinion go, I would almost always recommend a boiler + an indirect. And so would most every knowledgeable pro - under most circumstances. But that doesn't mean that's the correct choice for your application.

    A combi unit is one that does both space and domestic heating in ONE appliance. A boiler + an indirect is NOT a combi; it's two appliances.
    Bob Boan







    You can choose to do what you want, but you cannot choose the consequences.
  • delta Tdelta T Member Posts: 481
    Where are you getting those heat loss numbers from? Not disagreeing with them, but just curious. Heat loss is not done on a per sq ft basis, but on the actual construction of the building, type of radiant system used, insulation under the slab, insulation on the edge of the slab (very important factor that many don't take into account) and air infiltration (usually your highest single source of heat loss).

    As per your question, I always prefer a boiler with an indirect water heater. Least amount of maintenance, best efficiency (usually), and longest life (assuming a stainless steel indirect such as an HTP Superstor or a Lochinvar Squire.)
  • giceman1337giceman1337 Member Posts: 41
    I got the heat loss numbers from a supplier. I realized I misinterpreted the numbers and extracted meaning from them that was incorrect. I'm a noob.

    The specific numbers were
    21000 BTU Heating - 15 BTU/ft^2 * 1400 (included unfinished areas in this math)
    9087 BTU Radiant Back Loss - uninsulated 4" slab, 6" exterior wall R19 (1) and poured foundation below grade with foam insulation (3), finished ceiling.

    I then just doubled this estimate for the main level.
  • IronmanIronman Member Posts: 3,989
    You need to do an ACTUAL SCIENTIFIC heat loss calc. It's the foundation for sizing and designing everything in the system. Guessing, assuming and quick square footage calculators are worthless and grossly inaccurate.

    SlantFin has a free app that you can download and it will get you close enough - if you input the correct info and choose the correct construction data.
    Bob Boan







    You can choose to do what you want, but you cannot choose the consequences.
  • giceman1337giceman1337 Member Posts: 41
    edited January 11
    I have looked at a couple of the apps and I don't even understand the information they are asking for. Any help in input parameters would be greatly appreciated.
  • giceman1337giceman1337 Member Posts: 41
    I think I figured out SlantFin. My data is pretty close to what I had before. I came out with 29698 BTU for my 1400 ft^2 basement. I need to work the main level.
  • BrewbeerBrewbeer Member Posts: 397
    edited January 11
    Are you heating with natural gas? If so, you can get a good heat loss estimate using your gas consumption.
    A scientific room-by-room heat loss calculation in a spread sheet looks like the attached file. If you are handy with a tape measure and a spreadsheet, it's worth looking at.
    Hydronics inspired homeowner with self-designed high efficiency low temperature baseboard system and professionally installed mod-con boiler w/ indirect DHW.
    My system design thread: http://forum.heatinghelp.com/discussion/154385
    System Photo: https://us.v-cdn.net/5021738/uploads/FileUpload/79/451e1f19a1e5b345e0951fbe1ff6ca.jpg
  • giceman1337giceman1337 Member Posts: 41
    My primary heat is forced air. The floor heating is supplemental to just have a warm floor under your feet.

    The boiler and/or water heater will be natural gas.
  • GordyGordy Member Posts: 7,586
    You should do radiant primary, and stage the forced air as supplemental IF the radiant can't cover the load. However you will not know this with out a heat loss for proper design.

    You will not feel any benefit from the radiant using them together.
    Saved the f/a for cooling......
  • GordyGordy Member Posts: 7,586
    edited January 11
    Over 29k for a basement seems high. Is this a walk out. Daylight? Especially if your previous construction detail is correct.
  • Mark EathertonMark Eatherton Member Posts: 5,671
    Combo Boiler for Hydronic and Domestic
    My actual preference would be a boiler (modcon) with a reverse indirect DHW heater. It keeps the boiler in the condensing mode, even when its doing DHW production.

    ME
    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • giceman1337giceman1337 Member Posts: 41
    I have a walk-out basement. 6" framed walls with R19 on exposed wall. The other 3 walls are below grade poured concrete with rigid foam insulation and thermal reflective coating. The floor is 4" poured concrete slab with no insulation.
  • Jamie HallJamie Hall Member Posts: 7,513

    ... The floor is 4" poured concrete slab with no insulation.

    Oh dear. That's too bad. You will be trying to heat an awful lot of dirt -- and possibly ground water -- that way...

    Jamie



    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.



    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • giceman1337giceman1337 Member Posts: 41
    edited January 14
    A friend I know with a radiant system and a domestic hot water uses this system from Westinghouse. Anybody know anything about using these?

    Otherwise I was looking at the Navien systems. Are these Combi systems different from a boiler and indirect?
  • Jamie HallJamie Hall Member Posts: 7,513
    Well... it seems to be a nice fancy high efficiency water heater anyway...

    If it were mine to do, I'd use a nice mod/con for the radiant heat, and whatever I wanted for the domestic hot water. That way you are using the equipment for what it's intended.
    Jamie



    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.



    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • giceman1337giceman1337 Member Posts: 41
    (Sorry, I accidentally edited my previous post instead of posting new).

    I need a good recommendation. My current water heater just died. What is a good boiler with indirect system to use? Very ironic since I was looking to replace it.
  • GordyGordy Member Posts: 7,586
    Mod/con boiler, and indirect. Far better control than that....
  • GordyGordy Member Posts: 7,586
    Look no farther than HTP, Lochinvar,many others well versed in hydronics, and DHW.

    Search the board for Navien, combi, and water heater radiant woes.
  • giceman1337giceman1337 Member Posts: 41
    Thanks guys.

    Mod/con boiler
    That looks like overkill for my needs. That seems like a commercial boiler.

    I think I received a quote on an HTP EFT combi-boiler. Are Combi systems different than boiler w/ indirect?
  • giceman1337giceman1337 Member Posts: 41
    One question I have always had on boilers and usage in the radiant flooring. The boiler produces water that is typically very hot (>150F), but the flooring will require relatively cool temps (100F). Does this harm the boiler to "over-supply" that much heat?
  • GordyGordy Member Posts: 7,586
    edited January 14
    A modulating condensing boiler can produce what your radiant floor needs easily. Actually the lower the supply water the better, it makes the boiler more efficient. A cast iron boiler would require a mixing valve to reduce the supply water temp to the radiant. It mixes some of the cooler return water with the supplied hotter water.
  • GordyGordy Member Posts: 7,586
    If you really want to up scale DHW production efficiency. Go with a reverse indirect.
  • giceman1337giceman1337 Member Posts: 41
    I feel like an idiot. I thought "mod/con" was a brand name. The first thing that showed up on Google was HTPs 6.5M BTU system.

    Mod/con = Modulating condensing boiler
  • GordyGordy Member Posts: 7,586
    Correct. Many different sizing slots. This is one of the reasons a heat load calc is very important.
  • giceman1337giceman1337 Member Posts: 41
    What about the pro/con of Combi vs Indirect Water Heater?
  • GordyGordy Member Posts: 7,586
    Pro takes up less space one unit does both.
    For some with limited space, and lower DHW needs its the right choice.

    Cons unless you get a high TDR ( turn down ratio) 10:1, 15:1 combi the unit has a very high btu input to make enough hot water instantaneously. Which translates to way more than necessary for CH (central heating).

    Of your water supply is high in chlorides, and or hardness the domestic HX will require higher intervals of maintenance.

    You will need to carefully analyze your DHW needs, expectations, and incoming water temps to decide if a combi is right for you. Don't expect to run dishwasher, clothes washer, and shower with a combi.
  • giceman1337giceman1337 Member Posts: 41
    edited January 14
    I completed my Heat Load using Slant/Fin App. Assuming I entered everything correctly, here's what I computed.

    Heating needs:
    Basement - 29698 BTU
    Main Level - 28681 BTU

    My DHW needs is 2 adults and 2 growing boys (8 & 6). I expect times of multiple showers occurring at the same time. I don't know about multiples showers + clothes + dishwasher (seems overkill).

    My incoming water in Minnesota is quite cold. I think it listed average of 45F.
  • GordyGordy Member Posts: 7,586
    I'm really not sure what you want to hear, or read on this.
  • giceman1337giceman1337 Member Posts: 41
    I am just looking to gather as much information I can. I figured if I shared some of my information it may help guide the responses.
  • giceman1337giceman1337 Member Posts: 41
    I don't know how to compute my DHW needs and size the boiler and/or Water Heater.
  • GordyGordy Member Posts: 7,586
    The boiler would be sized for your heating needs as close as possible. Just under 60k (output) so an input of 80 k. probably a uft 80, Lochinvar wh 80, Lochinvar KHN 80, Weil McClain etc. this size will be sufficient for producing DHW for an indirect of 40 gal.

    Many other choices. The ones I listed are 10:1 and 5:1 tdrs.
  • giceman1337giceman1337 Member Posts: 41
    Thanks Gordy. So if I am understanding the indirect tank doesn't need to be as big as normal domestic water heater because the boiler will be able to continuously reheat the water within the indirect water heater?

    Is 10:1 and 5:1 TDR the modulation efficiency of the mod/con? I assume higher is better.
  • hot rodhot rod Member Posts: 7,528
    Combo Boiler for Hydronic and Domestic
    The main attractions to Combi units are the small footprint, and instantaneous DHW production.

    The downside is they are often oversized to the heating load.

    Some brands have the ability to limit fire rate on the heating mode and ramp delay to help reduce that cycling.

    The Lochinvar Nobel, 110 which I have in my house can deliver 3 gpm or so on the DHW function and can be derated on the heating to 11,000. That would be a fairly good match up for your home.

    I'd guess Minnesota water drops lower than 45. Milwaukee water temperatures can drop to about 37F in winter months where it is stored above ground.

    We had a webinar back in December presented by Paul Rohrs from Lochinvar. It compared tank, tankless and comb pro and cons.

    This slide shows the range of sizes, DHW production and min firing rate for SH mode.

    Yes, if you have hard water you may be deliming yearly. It's a fairly simple task if you install service valves and buy a delime kit. Most homeowners can do the service. Plenty of You Tube videos on servicing tankless or combis.

    Here is the link to the 1 hour webinar.




    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
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