radiant heating

Discussion in 'Boiler Forum' started by fozzy12, Oct 31, 2008.

  1. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,126
    Location:
    New England
    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.
  2. fozzy12

    fozzy12 New Member

    Messages:
    27
    Location:
    North of Detroit, MI
    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
  3. nhmaster

    nhmaster Master Plumber

    Messages:
    3,189
    Location:
    S. Maine
    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.
  4. nhmaster

    nhmaster Master Plumber

    Messages:
    3,189
    Location:
    S. Maine

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

    Redwood Master Plumber

    Messages:
    7,450
    Location:
    Connecticut
    May I suggest reading my latest book...
    It covers everything you could ever want to know about radiant heating.

    [​IMG]
  6. fozzy12

    fozzy12 New Member

    Messages:
    27
    Location:
    North of Detroit, MI
    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
  7. nhmaster

    nhmaster Master Plumber

    Messages:
    3,189
    Location:
    S. Maine
    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.
  8. Bill Arden

    Bill Arden Computer Programmer

    Messages:
    584
    Location:
    MN, USA
    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: Dec 6, 2008
  9. CHRISUPNORTH

    CHRISUPNORTH New Member

    Messages:
    11

    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
  10. smokinjoe

    smokinjoe New Member

    Messages:
    12
    Electric wires are only good to warm the floor..Not much good to heat the room in cold areas..........
  11. nhmaster

    nhmaster Master Plumber

    Messages:
    3,189
    Location:
    S. Maine
    Look you arrogent Prick. I already said that I mis-read the post. You however, are free to do any damned thing you want with your solar heat. There's absolutly no point in arguing with you because, even though 99% of us that design and install radiant systems would never run 150 degree water through the floor, explaining it to you is a total waste of time. Go crawl back under the rock you came out of. Be sure to tell all your idiot friends how you one upped an expert. Should make for a good drinking story.
  12. CHRISUPNORTH

    CHRISUPNORTH New Member

    Messages:
    11

    I dont know either of you guys so I am not taking sides but Id like to make an observation.....

    I have been reading this forum for a month now. People like me come to sites like this to learn from more experience and knowledgable people. I believe that nhmaster is likely a wealth of knowledge and everything he claims to be. I have also read many of his posts and he for some reason prefers not to share what he knows. Many of your posts (nhmaster) are one line, or even one word responses. If a guy asks if he should use a monoflow system (whatever the hell that is) You should say no and then explain why. Then the guy asks you what you recommend and you reply "LOOP". The way you are answering peoples questions are in my opinion a big waste of time and useless. I get the impression that you are more concerned about making everyone think you are the "Master" rather than helping people with their problems.

    It can be very frustrating when people reply with non-answers. Personally I believe that if you want to help others you should put every effort into it or just dont bother.
  13. nhmaster

    nhmaster Master Plumber

    Messages:
    3,189
    Location:
    S. Maine
    Well, you may have a point but experiance tell me that a long, convoluted answer is usually followed by other endless questions leading to the land of no where. Unfortunatly, without actualy being there, giving a detailed answer is often a waste of time. I do however answer an awfull lot of PM's, one on one. Let's take the guy with the mono-flow. If I spend a paragraph or two explaining restriction and flow curves, the very next post will be someone that has done it and it works fine. I post accepted engineering and installation practices. That there are bazillions of home designed, hair brained set up's that work is another matter altogether.

    I will however post here the most usefull solar link that I know of. www.caleffi.com Then download pdf file Idronics
    3
  14. Bill Arden

    Bill Arden Computer Programmer

    Messages:
    584
    Location:
    MN, USA
    Just remember to add foam insulation under the slab.

    With under-slab insulation it could be used to heat the room even in cold areas.
  15. redwoodvotesoften1

    redwoodvotesoften1 New Member

    Messages:
    78
    This thread gives me an interestin idea...
    Whachawl think about a solar heated still for making up my moonshine...
    Thats funny right there ya awl I don't care where yur from...
    Solar powered, Moonshine!

    Maybe NH Master needs a sip o my shine...
    Prolly keep his head from explodin.
  16. nhmaster

    nhmaster Master Plumber

    Messages:
    3,189
    Location:
    S. Maine
    Though possible, solar power would limit shin'in to sunny days which might be a problem, then again, maybe not. Anyhoooooooo. Will need to see the performance curves and gpm flow rates for the evaporator as well as a sample ( a gallon should do ) of the finished product for evaluation. In the meantime a good old wood fire should keep her up and running.

    If you am too durned drunk to notice over the next day or so Merry Freekin Christmas and to all a good night. :)
  17. redwoodvotesoften1

    redwoodvotesoften1 New Member

    Messages:
    78
    Merry Freaking Christmas to you too NH Master!
    I'll be sending a special jug your way. It wrung out at 150 Proof and we're going to call it Northern Comfort in your honor.
    The extra zing should do well to keep you warm this winter.

    I jes wanted ta let yawl know that Southern Man is doing okay now.
    He kinda wen offfa the deep end when yawl started pickin on im.
    He stayed down by my still fer quite a few weeks jes sippin on the hose whenever he woke up then passin out again.

    Anywho he finally stopped drinkin and sobered up... took a few days but I got him helpin me on converting the Whirlpoof gas water heater to a still down in my basement. He's been puttin all sorts of fancy temperature controls together and he says this is gonna be is finest work ever. He says that this thing is gonna be completely automatic... Some sort fo fancy computer thing called a PLC is gonna control the whole process.

    I tell ya wen he ain't drinkin he's a genius!:D

    After we git r runnin on gas we'll be workin on the solar portion of the project!
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