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I need a path forward. Any suggestions?

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by Jeff Childers, Apr 13, 2012.

  1. Jeff Childers

    Jeff Childers Member

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    I have a radiant floor installed which uses a propane fired tankless water heater to heat the water. It is too expensive for us to operate and I want to change the way I heat the water. Can I simply install a small boiler in the basement and change the hot water supply line for the radiant floor from the old tankless heater to the new boiler output? It seems like it should work. I can get all the free wood I can use so a small boiler would costs almost nothing to operate. Are there smaller, less expensive, boilers made just for this application? Thanks for any ideas.

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  2. jpgarnva

    jpgarnva New Member

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    That was exactly the same problem we had. The propane gods were bleeding us dry. We did put in the wood boiler and ended up making a primary loop with it via heat exchanger that also allowed us to keep the propane as a back-up. Hope it is just a trophy of where we don't want to be.
  3. Hunderliggur

    Hunderliggur Minister of Fire

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    We have a tankless as a backup and a wood gassifier as the primary to 1000 gal of storage. It costs me $1 or more an HOUR to heat the entire house with propane in the deep of winter. That is my tradeoff with wood - every hour I heat with wood I save a dollar. Makes the payback period seem so much more reasonable.
  4. Gasifier

    Gasifier Minister of Fire

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    Remember that heating with wood will change your life, or lifestyle. It is a lot of work. I like the work, most of us on hearth.com do. Some buy their wood cut/split/and delivered. I do sometimes if I have the money and don't have enough time. A lot of us cut our own for the added savings. Your water heater puts out the water at a lower temperature. I do not know if you use a mixing valve to get it to the right temperature for the radiant. ? But you will need to get it to the right temperature for the radiant from the wood boiler temperature. You will also need a return boiler protection valve. A gassification boiler and well insulated water storage is the way to go. If you can afford the storage now, great. If not, pipe or set up your system so you can add it in later. Burning your wood flat out and storing that energy in the storage tank(s) will help you get the most efficiency out of your system. Ask lots of questions here. Good luck. Start getting your wood supply going now. You need dry wood. Learn about types of wood, seasoning or drying it, which ones dry quickest, etc. The Wood Shed forum is a great place to learn about that. With any wood burning appliance you need nice and dry wood. 20% moisture content or there abouts. Later. What area of the country do you live?
  5. ozzie88

    ozzie88 Member

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    I have a Gasser and just taped into the first floor 3/4" line with 3/4 Orange Pex. to heat floor added a gate valve to adj. temp. of water flow to floor,works great. You HAVE to use the orange Pex line rated for wood boilers at 200*, I did my bath and hallway added 100feet and pump did fine with extra line.
  6. Gasifier

    Gasifier Minister of Fire

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    Interesting. So you use a gate valve to mix the cold water in with the hot water to get the right temp. How do you know what the temp is after it is mixed in? What does the temp have to be? If I remember right the water that gets mixed before it goes into my garage floor goes into the concrete at 110 or 120? Does that sound right? I would have to look at the mixing valve to see what it is set at.
  7. ozzie88

    ozzie88 Member

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    I taped into the first floor baseboard loop just before it goes into bathroom, So the gate vale just cuts down water going threw loop[bath baseboard] so it goes threw the 100Foot Orange Pex line. The temp will be what ever boiler is putting out,,around 170 to 200*. I just thought if I wanted floor warm I be running boiler anyways.Anyways Im cheap,lol
  8. ozzie88

    ozzie88 Member

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    I taped into the first floor baseboard loop just before it goes into bathroom, So the gate vale just cuts down water going threw loop[bath baseboard] so it goes threw the 100Foot Orange Pex line. The temp will be what ever boiler is putting out,,around 170 to 200*. I just thought if I wanted floor warm I be running boiler anyways.Anyways Im cheap,lol
  9. Gasifier

    Gasifier Minister of Fire

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    That is interesting. I guess the pex that my guys used to do the concrete floor in the garage must not have been rated for that temp. But, if you were to install new. Would you use the higher temperatures to heat the floor with radiant? Or is there a reason that they seem to use a lower temp? In other words. Do you get better efficiency by using lower temps. If boiler puts 180 degree water into storage, and you only need 110 degree in the radiant. That higher temp water would last you longer? Or am I thinking wrong? :( That is always a possibility. ;lol I am getting some more caffiene right now. It has been a long day.
  10. 711mhw

    711mhw Feeling the Heat

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    Gassifier, your right, the beauty of radiant is the low water temps needed. I think that there is a recomended limit to the water temp that you can safely put through the concrete. How the heck do you "quote" in this new version here?
  11. Hydronics

    Hydronics Feeling the Heat

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    As I recall 120 is the max continuous temp to a radiant concrete slab.
    Click the reply button at the bottom of the persons post that you want to quote.
  12. woodsmaster

    woodsmaster Minister of Fire

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    There is no limit to the water temp you can put in a cement floor, at least no limit that our boilers will exceed. You can run 190 F water all the time if you want with no problems to the floor. The problem is with efficiency and over shooting floor temps.
  13. EffectaBoilerUser (USA)

    EffectaBoilerUser (USA) Member

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    The biggest advantage with a gasser and large storage AND radiant floor heat is that you are able to store a very large amount of useable hot water (BTU's) in your storage tanks (WATER BATTERIES) without having to purchase an oversized (or even real large and more expensive) boiler. For example, if you have a 1,500 gallon WATER BATTERY(storage tank) and you CHARGE IT TO 190F and are able to heat your concrete radiant floor with 100 F water, you have 1.1 MILLION BTU'S OF STORED ENERGY/HEAT!

    Using a smaller boiler (say 35-40kW) you can make back to back burns and input the approx. 1.1 million BTUs of heat into the oversized tank.

    Brian
  14. ozzie88

    ozzie88 Member

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    My boiler runs at 180 to 200 sometimes 210* so I wanted a Pex pipe rated for thisand is also rated at 70-80Lbs at these temps. The heat goes into the house anyways so warmer floos for my toes,,,
  15. Fred61

    Fred61 Minister of Fire

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    The answer your question is Yes! If you are using potable water for your radiant, you must isolate the boiler water from the tubing via a heat exchanger. From there it should go through an adjustable tempering valve which mixes return water from your loop with new make up water from your storage and circulate it through your loop.
    When I was ready to purchase my boiler, I had first wanted the Biomass but I chose the EKO 25 because of the lower btu rating. When I first chose to install radiant in my house, I went with Radiant Floor Co of Barton Vermont. Since my baseboard hot water system supplied by a Peerless boiler was working fine, there was no need to rush on the installation. It was just one more improvement to my retirement place that had turned out to be a hobby for me. It was ; buy the tubing this year, store it 'till next year and install it. The heat source was supposed to be a tankless heater or a Polaris water heater. During that time I decided to install a wood boiler for the heat source. Having been ignorant about the lack of on barrierrier at the time of purchasing, I discovered that since the heat source was going to be my water heater, the tubing did not have oxygen barrier.
    I ended up installing the boiler with a 500 gallon storage tank that has a 200 foot long coil of 3/4 inch copper tubing. Works great! I light one 4 or 5 hour fire a day and run off the tank for the remaining 20 hours. Domestic hot water comes from the same circuit. I also put a coil in the bottom of the tank that cools the boiler in case of overheat.
    If your system is using potable water, I suggest you get the design booklet from Radiant Floor and after studying their designs you will know exactly where to cut in your wood boiler. Their schematics will also show you how to plumb so that the water in flushed through the lines everytime you turn on your water.

    BTW (aferthought) With the addition of two zone valves and a sensing control on the tank your tankless heater becomes your back-up.
    Also you asked about smaller "less expensive" boilers. My opinion? There aren't any.
  16. ozzie88

    ozzie88 Member

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    Another way is to just add another cirulater pump and thermostat and have the floor just like you want it. This orange pex is only pex for wood boiler 200* and Oxygen barrier. Red Pex is for 180* and Oxygen barrier ok just not high temp rated.
    I dont understand need for mixing valve for floor??

    Attached Files:

  17. Fred61

    Fred61 Minister of Fire

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    If I didn't mix to lower temperature, the floor would be so hot that when the room thermostat was satisfied, the floor would continue radiating until room temperature was about 80::F. Then wait for the room to cool down to start the cycle all over again. I prefer low-n-slow for comfort. The Honeywell AM series 1 mixing valve is hard to beat for maintaining desired temperature instead of alot of other hardware.
  18. ozzie88

    ozzie88 Member

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    that sounds like good idea.my bath and hall is so small dont really matter but in bigger places I can see where this be good idea.
  19. Jeff Childers

    Jeff Childers Member

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    Fred61, You and I may have made the same mistake. I, too, installed a Radiant Floor. I have an open system so that my potable water runs through the slab before it is used in the house. Should I convert to a closed system if i use the boiler? I never really understood why we hooked up the water the way the Radiant Floor guys asked us to, so maybe this is a dumb question, but why wouldn't a simple closed system (with expansion tank) work best in this case? It seems like a quick and simple conversion. I have the Radiant Floor installation diagrams to reference if needed. (they are also available online).

    I have the red PEX that I think is rated to at least 100 PSI. I don't know the input temperature of the water in the propane-fired system but I am assuming I could mix cold water into the pipes to make the boiler output exactly what it needs to be to work in my system.

    About that "smaller, less expensive" comment, I would like to minimize my additional cost. How many gallons of water (or maybe I should say "What size boiler") should I be looking for if I have 2,500' of 3/4" PEX in my slab? I won't make the change if it means I have to buy a $5K boiler. I hope there is a cheaper solution, especially since I have already invested so much into the PEX and Radiant Floor.

    General info because someone asked - I live in South Central Tennessee. The house is 5,400 sq. ft. but I am only trying to solve the heating problem for the 1st floor which is about 2,500 sq. ft.

    I'm encouraged to continue my search. Thanks for all of the good info so far!
  20. Hunderliggur

    Hunderliggur Minister of Fire

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    I also have the Radiant Floor Company design of potable water in the heating loop. I have an in-tank heat exchanger in my top 500 gal storage tank. The HX output is sent through a mixing valve with the return water to limit the HX output to 130F.



    There are several advantages to the potable in the heating loop design, particularly with a tankless water heater as your backup or primary heat source:

    1. Floor loops never stagnate for months at a time. Maybe not a big issue with treated, closed water, but the potable in the loop design has fresh make-up water for DHW moving through the loop year round, never stagnating.
    2. Water delivered to the tankless system is always tempered before heating. The floor loops will always be room temperature or above. You use much less DHW at a time than you do in your floor loops. The input to the tankless boiler will be 70F +/- instead of your cold water supply temp (55F here in my part of Maryland). During the heating season, the tankless input will be your return temp 100F +/-. You'll never notice the heat change in the radiant loop unless you are running a car wash or something.
    3. You can (carefully) use your floor loop for radiant COOLING. I have a bypass set up that runs ALL of my potable water use through the first floor loop in the cooling season. My arrangement does not cool the floor below the dew point in my area so I don't have a condensation issue (I check, it is an open ceiling in the basement to inspect the radiant zone above). I calculate I get about the same cooling as a typical window AC unit as a byproduct of irrigating anyway. I use a single sprinkler at about 3GPM I believe which works fine for the cooling. If you do this, make sure you are not getting condensation on the radiant loop. Use a mixing valve if you have to.
    I don't think I made a mistake with the Radiant Floor company design. It works well for my application and probably many others. It is different that the "typical" installation, but when has anyone here on Hearth been typical of anything!
    Mark
  21. Fred61

    Fred61 Minister of Fire

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    I don't feel that I made a mistake at this point. I was a little discouraged at first when I realized that the tubing lacked oxygen barrier but after cruising this forum foe four years, I feel like I have an advantage over many closed systems such as DHW without sidearms,etc.

    Unless you installed oxygen barrier tubing, which I doubt you did, you really can't change to a closed system.
    I really can't tell you what size boiler you need since I don't know the heating requirements of your home, however I think you should probably scrap the thought of installing a wood boiler for $5K or less.

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