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  1. #1

    outdoor fireplace with radiant/ventilation system

    I am working on designing a outdoor fire place with a knee wall surround as a wind break.
    I would like to implement some type hydronic/radiant heat flooring system as I would be laying a concrete patio/base with architectural stone surface.
    My thinking is some type of tank next to the chimney to absorb the heat from the fire place.
    However I need to work out some kinks as I am not very skilled with this type of system. ie: controls/vavles
    Would like to keep as much of this system mechanical (controls) as possible.

    Some issues I have are :
    1. Could I use a typical automotive type anti-freeze solution either straight or mixed ? My concern here is possible damage to the system & or concrete during winter or non-use.
    2. What type of controls/valves would I need/could use.

    3. How would I figure load calcs. for a system of this nature. ie: tubing weave and size of tubing.
    I would also need to make sure I have tank/radiator large enough to handle the load requirements.


    I will also be using dead spaces behind the actual firebrick/fire place to install a squirrel cage ventilation system as a supplemental heat, venting out the front of the fireplace if needed.

    Any help or input in regards to any of these thoughts would be greatly appreciated.

    It will probably be next spring/summer before actually starting this job as I am still working out some issues and its pretty cold here now but will post some pic after completion.

  2. #2
    Join Date
    Aug 2004
    Location
    S.E. Pa
    Posts
    6,304

    Thumbs down Yikes!

    Make sure your life insurance is paid up.

    This is bad from so many angles I don't even know where to start. No, no, and no.

  3. #3
    Join Date
    May 2002
    Posts
    9,564
    There are rules on using radiant in an outdoor setting. Check with the local municipality. You cannot use a damaging glycol and you will need to use a eco-friendly glycol.

    Your biggest issue will be the design with appropriate pressure relief and design so you don't flash off steam and blow something up. You need an engineer for that I'm thinking because you have to be careful about sizing. This is important because when water turns to steam it suddenly occupies 1728 times the space. That can make for a very explosive situation.

    I think putting in a little solar with a tank would be easier and less expensive in the long run.

    However, to counter the previous post engineers have been designing and manufacturing wood boilers for many, many years so it's not out of the realm of possibility as it is cost.

  4. #4
    please explain, what exactly it is you have issues with as I may not have explained it in great detail.

  5. #5
    sysint,
    my bad about the non eco-friendly glycol,however they do have eco-friendly which they use in closed loop geothermal systems,just not not real familiar what kind that is or where to purchase.
    as for the expansion of the liquid you have a very valid point.

    hearthman,
    please,please do explain you make it sound like I am trying to suspend a 30 story high-rise by a balloon, as sysint said they have done similar type systems before its just not widely used.
    As for the venting system it is not going to blow directly on the fire.
    The tank would not be right over the fire.

    As I said I am in the design phase and there are some issue to be worked out yet, I was looking for some input from some one more skilled in these areas, may be this is to elaborate for you to grasp!!!

    "FIRE SO EASY A CAVEMAN COULD DO IT"

  6. #6
    Join Date
    Aug 2004
    Location
    S.E. Pa
    Posts
    6,304

    Thumbs down homemade systems

    My point is, homemade boilers tend to blow up and cause damage. You really should limit yourself to a tested, listed system. The building code specifiies how to build a masonry fireplace and nowhere in it does it include incorporating a boiler. The code further requires boilers and pressure vessels be tested and listed. Your AHJ would have to approve of the boiler even if tested and listed, much less homemade.

    In order to make an effective heat exchanger in a fireplace, you would have to violate the code requirements for wall thicknesses and materials. If you build the fireplace to code then try to incorporate a boiler, it will be so far from the heat, it won't be worth it. Now, add to that the sporadic use of a fireplace, the sporadic firing rates, the pollution, low energy efficiency and it just does not add up. What if a valve freezed up? What if this thing blows up? Will it take out neighbors? House guests?

    You would have to get all this approved by your fire marshal, building dept. and possible the State and your insurance carrier, who I'm sure will run like heck from this and cancel your insurance if they find out you did it.

    Hey, heat your patio however you like, as long as it meets code and was inspected. Of course, outdoor radiant heat is a huge waste of energy but I guess that's not a concern of yours here much less the pollution.

    The hearth industry went through a learning curve back in the '70s and '80s. When enough people had bad outcomes, changes were made to the codes and stds. to weed out the bulk of the problems and homemade heating appliances remains near the top of that list next to DIY installations.

    The negatives of this setup grossly outweigh any possible positives I can see. Just my tuppence worth....

  7. #7
    Join Date
    Apr 2002
    Posts
    1,383
    You are proposing to design a system which will collect significant amounts of heat from the fire and then distribute it through a relatively distribution system.

    Your description of putting a tank next to the chimney to absorb heat suggests that your understanding of how to design a boiler system is negligible. That's not surprising -- it's a complex subject.

    Other have suggested the hazards of a poorly designed system. Their concerns are well founded.

    Reading your post suggests that it's very unlikely that you have the knowledge to design a safe and effective system to do what you want. Were you to try to get a building permit to do that, I'm guessing your local authorities would refuse to issue one.

    Unfortunately, I think Hearthman's assessment of the risks of this project are entirely accurate.

  8. #8

    post #6 & #7

    First & foremost I never proclaimed Boilers or fireplaces to be my area of expertise, with that said you both have valid points. Some county's around here don't even have building dept./inspections to consult with.

  9. #9
    Join Date
    May 2002
    Posts
    9,564
    I don't think he is looking to make a boiler. He is looking to make a heat exchanger. Anyway, there are many manufacturers out there today that make add-on exhaust stack heat exchangers for boilers. I'd contact one of them. I can think of Cain Industries for one.

  10. #10
    Join Date
    Apr 2002
    Posts
    1,383
    My intuition tells me that it would tend to take a lot of BTUs to heat up an outdoor patio or recreation area with an in ground heating method.

    It also tells me that improvised methods of scavaging heat froma fireplace are not going to produce many BTUs.

    Therefore, I conclude that this idea is not going to pan out.


    In addition to that, you have the risks of a pressure vessel explosion if hot water isn't properly managed.

    Aside from those issues, no problem!



    Seattle Pioneer

  11. #11
    Join Date
    Apr 2002
    Posts
    1,383
    Hey Coool J----

    Have you considered one of those radiant propane heaters on a tall stand as a means of heating your patio area? That's liable to be a lot simpler and less costly, and provide predictable results.

  12. #12
    Quote Originally Posted by SeattlePioneer View Post
    Hey Coool J----

    Have you considered one of those radiant propane heaters on a tall stand as a means of heating your patio area? That's liable to be a lot simpler and less costly, and provide predictable results.
    Have seen them around, Just not in use. The one concern with them is how effective it would be chillin in a chair. We all know heat rises.

  13. #13
    Join Date
    Apr 2002
    Posts
    1,383
    Quote Originally Posted by COOL J View Post
    Have seen them around, Just not in use. The one concern with them is how effective it would be chillin in a chair. We all know heat rises.


    Radiant heat doesn't rise. It moves out in a fairly straight line and is typically reflected fairly efficiently by these deck heaters.\

    As soon as the radiant energy is absorbed by some object it becomes heat that will rise.


    I've seen these heaters sold for less than $200. You might want to experiment with one --- my guess is it would be a far better investment than the engineering and construction project you are considering.

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