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Radiant in a flower bed

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That's exactly what I've seen and read about for <I>greenhouses</I>. Unless I missed the mark this planter is in a house for humans where the soil will already stay in a nice "cozy" range for most seeds and cuttings--let alone the plants themselves. Unless the customer says something like, "I'm growing such-and-such sub-tropical plants that must have soil temps that <B>never</B> dip below say 60F I just can't see a need.

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  • Jim Pompetti
    Jim Pompetti Member Posts: 552
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    Radiant in a flower bed

    While installing radiant in a concrete floor, we were asked to install radiant heat in an indoor flower bed that is in the same space. The customer fears the flowers are too close to an outdoor wall/windows and may become too cold. My concern is that if the tubing is buried 24" deep, will it ever heat. Will this affect our heat loss in the room? The bed will be 2' deep x 2' wide x 14' long. We are installing an insulation barrier on the bottom of the bed and on the outside wall.
  • Mike T., Swampeast MO
    Mike T., Swampeast MO Member Posts: 6,928
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    Are there some sort of exotic plants with truly unusual requirements being grown/germinated/rooted?

    For germinating most seeds and rooting most cuttings 65F-75F is the ideal range, so normal room temperature is essentially perfect. Somewhat cooler nighttime soil temperature is fine and even sometimes desirable. The soil temp would have to drop to 50F-55F for there to be any problem with germinating or rooting. Once actively growing, most plants will tolerate a much broader range of soil temperature. Again, it would seem that "typical" indoor temperatures produce a nearly perfect soil temperature for most plants. With insulation at the bottom and against the outside wall, I don't see any need for soil heating unless the customer has extremely specific requirements.

    Greenhouses do sometimes use soil heating as it can significantly reduce winter heating costs. Seeds will germinate nicely and many plants will grow perfectly with quite cool air as long as the soil itself is in that 65F - 75F range. Exterior windows boxes are another fairly common application for soil heating.

    I've seen flowers blooming on window sills in the dead of winter. I have a number of citrus trees in pots that come in each winter. The largest and heaviest (say 300#) is a grapefruit tree that always winds up pushed against a north-facing sliding glass door in the basement with the fruit growing and usually ready to pick in late winter.

    Always give the customer what they want, but you might politely suggest she talk with a good local nursery or greenhouse to see if there is any need.
  • Ken_40
    Ken_40 Member Posts: 1,320
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    Jim,

    It works, and works like a charm.

    We helped a recent Rutgers grad nurseryman in central NJ who heard about micro-tube grow tables. He is the foremost geranium grower in the area and has two 300' long greenhouses. He uses the micro-tube radiant on top of isumlated grow-bench tops and places the starter pots on the warm micro-tubes so that the dirt and cuttings are ~ 60 F all winter, while the greenhouse is in the high 30's.

    Apparently the root temperature is more important than the above ground plant and despite geraniums being very frost prone - above ground, the root/cutting portion kept warm, grows like mad. Fact is, the thousands of plants, dirt and pots create a flywheel heater affect and the greenhouse's extreme low of ~40 is more than enough for growth of the new plant! Sunlight during the day kills the pump and solar alone does the job all day. During the cold winter nights, basically the moment the sun goes down, the boiler and micro-tubing begins its temperature climb to offset the lost sun.

    On cloudy days, the stat drives the system. Being that large an area, there are a bunch of ball valves for manual tweaking - should not all grow tables be in use.

    If memory serves, it's a 2-pipe reverse return setup. I believe for the 300 X 75' house, he ran 2" black out, and back.

    Keping the roots cozy is the apparent key. The energy consumed was 1/6th what he had before when he tried to heat the entire "house."

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  • Jim_65
    Jim_65 Member Posts: 184
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    Josh (the Youngster)

    When Josh first went into business he did a system very similar to what you are inquiring about.

    Maybe he can add to the conversation...
  • Jim Pompetti
    Jim Pompetti Member Posts: 552
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    Ken

    Nice hearing from you! This set up is one loop on a 4 loop manifold . The other 3 heat are in the living area , so do you think that will cause me to have any problems heating the space .
  • Ken_40
    Ken_40 Member Posts: 1,320
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    Jim,

    We did have a nice time at NYC BU didn't we!

    Sounds like one pump and four loops? One dedicated to a nursery area that is a relatively small load?

    It's hard without pictures, but I would think the tubing, assuming PEX would be the choice, would be prone to wear! Between chafing fine soil, soil tilling and working and implements for care or dirt replentishing, the danger - even down 24" - is real for a puncture.

    Placing the tubing on wire mesh cut to size and 4" of concrete wheelbarrowed over the tube might make a helluva an emitter? Then too, just using one inch black pipe as the indirt emitter would also work nicely. The black pipe radiant system used in the non-growing potting areas of my example has been sitting in the greenhouse floor dirt, somewhat exposed in a few small areas, is over 20 years old Other than a rust patina on its surface, it is very much in good shape. So, sched.40 pipe may be fine indeed. The surface area of steel pipe is the equielant of 5 or six runs of 1/2-3/4 PEX so even lower temps may be warranted. The puncture proof merits attention as well?

    What I suggest is either PEX in wire reinforced concrete, or steel pipe straight (no concrete).

    The biggest problem may be getting the root radiant to control its environment regardless of the rest of the system's on/off status. Three-way zone valves might do it.

    But the circulator, ZV and control array sounds straight forward. Unless you're being asked to do all 4 circuits merely by balancing?

    Insulating the underside and wall exposed aspect will cut root area losses a lot. But glass is glass, even double pane. Or is this a supplimental grow-light app?

    Let us know what happens. This is an extremely interseting radiant application.

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