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Thread: radiant heating

  1. #16
    Master Plumber nhmaster's Avatar
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    Well I guess that makes you the current expert on the matter. So if you don't mind dancing around on a 150 degree floor then by all means go for it. The rest of us however will be content to design radiant systems that use water temperatures that are comfortable for human occupation.

  2. #17
    Master Plumber nhmaster's Avatar
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    So is the floor temperature 95 or 150 degrees?

  3. #18
    Plunger/TurdPuncher kingsotall's Avatar
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    "How's the floors¿"

    "Great, no, just great! Really!!"


  4. #19
    Computer Programmer Bill Arden's Avatar
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    Quote Originally Posted by witch View Post
    Well the way my solar hydronic systems works, the floor warms up, the heat transfers to the air space and the thermostat reaches it's set temp, and turns that zone off. The floor in my bathrooms (tile) may reach 90-95 degrees before the thermostat, set at 75, turns off that zone. Floor Temp needs to be higher than about 90 degrees before it feels warm to the touch, so no problem with 150 degree floors in my house.
    Witch
    I am going to translate that as saying "I don't have a problem with hot floors since the floor itself does not get that hot"

    -
    I'm playing around with a non UL approved "research" set up as well.

    Here's what I've got so far
    1. A bronze recirculation pump
    2. In floor PEX
    3. A plastic non-pressurized tank. (open air system)
    4. Plans for a solar trough that will still work at -40F.
    5. Two 50 gallon hot water heaters with internal 30sq heat exchangers.

    I have to use copper, PEX, or brass for corrosion reasons. (open air)

    It is legal to use a hot water heater to heat potable water and then use that to heat the floor via a heat exchanger.

    It is also legal to use the hot water to directly heat the floor, but that means there is no way to use antifreeze.

    Note: to stay legal, you would have to have some sort of sink to justify having the hot water heater there and to use some water. I would also recommend adding a check valve before such a long and possibly "stale" section of water pipes.

    To stay safe you have to have a "safety" expansion tank on the potable water side AND use non-toxic antifreeze on the heat side.

    One reason they don't like hot water heaters being used for in floor heating is that you can not use antifreeze with a hot water heater since even the fold back elements tend to scorch and burn the antifreeze.

    Electric boilers designed for heating are carefully designed to maintain fast water flow past the elements and this keeps the element surface temp below the point where the antifreeze starts to degrade.

    I could build my own boiler that would be safe, but is it really worth my time.
    Important note – I don’t know man made laws, just laws of physics
    Disclaimer: I'm a big fan of Darwin awards.

  5. #20
    Master Plumber nhmaster's Avatar
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    What?

    Are the damned floors 150 degrees or not? Not a complicated question I think.

    If you want to use an electric water heater than by all means go right ahead. You are the one paying the bill. However all you cowboys need to understand that there are mechanical codes that regulate the installation of all heating systems and to insure that your insurance will pay off when the house floods or burns down, you need to get the system inspected and signed off.

  6. #21
    Retired Defense Industry Engineer jadnashua's Avatar
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    Depends on how close the tubing is to the surface...the probe you have is probably located between the runs, or on the wall. Peak temperatures right over the tubing could be considerably higher than that midpoint between two runs. You're measuring average, not peak temperatures. It could become especially problematic if heating a cold slab verses one that has stabilized at the desired temperature...the difference between peak and average temperatures would be much greater...you have to account for these boundary conditions if you want a safe system, thus the lower input temperatures. You have to realize it will take awhile to bring a large mass up to temp.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  7. #22
    DIY Junior Member fozzy12's Avatar
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    Default Update on Radiant heating

    I see this original thread generated a lot of posts about radiant heating methods. My system is up and running here in Michigan where the weather is getting pretty cold. So far my building is uninsulated and the second floor staple up piping is getting finished. This is a garage and the inspector has already been in to look at the slab piping prior to the pour. Hot water heaters are allowed in my situation because this is not a single family residence. My choice was a Brad White 75 gallon heater. It has input capacity of 75K BTU's which is enough after efficiency to provide enough heat for what I need to do. So far the system has run three days and the slab is 75 degrees with an outsided temp of 25 degrees. I have to finish and have an inspection both electrical and mechanical before I can insulate. So far I'm pretty impressed wth the system. It uses Grundfos pumps, I have 2 zones. It's running about 23 pounds of pressure and I can monitor input and output temps. I have only one circuit running right now, hope to have the second one up soon.

    The piping is 5/8" pex. All of the fittings that came with the system appear to be very high quality. The pex fittings are the ferrule type with large nuts to secure them. Everything was air checked prior to putting water in the system and it was all tight. So far I'm very impressed with the equipment that I purchased from the supplier in Vermont. I did check the website that was recommended by someone and read the comments about the company there. The posts were over a year old. Not sure what to say about them short of mine is a closed system, not an open one, so some of the observations made about open systems would not apply to me. They have always gotten back to me with answers to my questions and to their credit and heat calcs, the system appears to be working fine.

    Eric

  8. #23
    Master Plumber nhmaster's Avatar
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    I did read your posts and they make no sense at all. If your floor temps are running 90 - 95 (which is normal) they why run 150 degree water through them? Lower the temperature to 95 and let the circulator run longer. You will pick up a signifigant amount of efficiency, boiler wise and longer cycle times on the circulator save money also. Also you shouldn't bu running a wall thermostat on a radiant slab system. It should have floor sensors.

  9. #24
    Master Plumber nhmaster's Avatar
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    Quote Originally Posted by fozzy12 View Post
    I see this original thread generated a lot of posts about radiant heating methods. My system is up and running here in Michigan where the weather is getting pretty cold. So far my building is uninsulated and the second floor staple up piping is getting finished. This is a garage and the inspector has already been in to look at the slab piping prior to the pour. Hot water heaters are allowed in my situation because this is not a single family residence. My choice was a Brad White 75 gallon heater. It has input capacity of 75K BTU's which is enough after efficiency to provide enough heat for what I need to do. So far the system has run three days and the slab is 75 degrees with an outsided temp of 25 degrees. I have to finish and have an inspection both electrical and mechanical before I can insulate. So far I'm pretty impressed wth the system. It uses Grundfos pumps, I have 2 zones. It's running about 23 pounds of pressure and I can monitor input and output temps. I have only one circuit running right now, hope to have the second one up soon.

    The piping is 5/8" pex. All of the fittings that came with the system appear to be very high quality. The pex fittings are the ferrule type with large nuts to secure them. Everything was air checked prior to putting water in the system and it was all tight. So far I'm very impressed with the equipment that I purchased from the supplier in Vermont. I did check the website that was recommended by someone and read the comments about the company there. The posts were over a year old. Not sure what to say about them short of mine is a closed system, not an open one, so some of the observations made about open systems would not apply to me. They have always gotten back to me with answers to my questions and to their credit and heat calcs, the system appears to be working fine.

    Eric

    Give us a ring a couple months form now and let us know what the electric bill looked like.

  10. #25
    Master Plumber Redwood's Avatar
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    May I suggest reading my latest book...
    It covers everything you could ever want to know about radiant heating.


  11. #26
    DIY Junior Member fozzy12's Avatar
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    Default radiant heat follow up

    To NH master,
    Mine is a gas fired system, it's not electric. I'm not sure where that thought came from. Electric powered hot water radiant heat makes no fiscal sense at all.

    Eric

  12. #27
    Master Plumber nhmaster's Avatar
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    Might be my own confusion. I have been involved with at least 3 threads on other sites, discussing the same issue and I guess I thought we were tak=lking about using an electric water heater. Gas water heater is slightly better, but not much and if it's propane fired, mighe even be worse. Problem with tank type heaters is the exchange ratio from the heat source to the water is signifigantly less than a boiler that uses multiple and narrow passages to scrub as much heat from the fire as possible.

  13. #28
    Computer Programmer Bill Arden's Avatar
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    Quote Originally Posted by fozzy12 View Post
    To NH master,
    Mine is a gas fired system, it's not electric. I'm not sure where that thought came from. Electric powered hot water radiant heat makes no fiscal sense at all.
    Eric
    I think it's my fault. I was saying that I was planing on using a hot water heater with an internal heat exchanger. but I am also planing other heat sources and the electric element will mainly be used as a backup.

    Edit:
    I also would rather see someone install PEX in the floor and use an electric boiler than install electric wires in the floor.

    The PEX system can be upgraded in the future, while the wires will fail.
    Last edited by Bill Arden; 12-06-2008 at 05:26 PM.
    Important note – I don’t know man made laws, just laws of physics
    Disclaimer: I'm a big fan of Darwin awards.

  14. #29

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    Quote Originally Posted by Bill Arden View Post
    Edit:
    I also would rather see someone install PEX in the floor and use an electric boiler than install electric wires in the floor.

    The PEX system can be upgraded in the future, while the wires will fail.

    I considered electric wires for my 250 sq' addition but I am putting pex in the floor and heating with an electric water heater (marathon).
    My reasons are simple. This will be for floor warming only to supplment existing FAG furnace. I did a heat loss calc on the addition and I only need about 10k btu's (without considering heat from the FAG furnace). A boiler, even a small one would have a initial install cost 15-20 times that of my electrical requirements per year.
    Makes no sense to me not to use electric.
    I didnt go electric wire floor because if it fails, I am screwed.

    C

  15. #30

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    Quote Originally Posted by CHRISUPNORTH View Post
    I considered electric wires for my 250 sq' addition but I am putting pex in the floor and heating with an electric water heater (marathon).
    My reasons are simple. This will be for floor warming only to supplment existing FAG furnace. I did a heat loss calc on the addition and I only need about 10k btu's (without considering heat from the FAG furnace). A boiler, even a small one would have a initial install cost 15-20 times that of my electrical requirements per year.
    Makes no sense to me not to use electric.
    I didnt go electric wire floor because if it fails, I am screwed.

    C
    Electric wires are only good to warm the floor..Not much good to heat the room in cold areas..........

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