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Thread: Greenhouse Update

  1. #561
    Join Date
    Oct 2009
    Location
    CT, USA
    Posts
    9,591

    Default Re: Greenhouse Update

    That is one heck of a set-up.
    "Please be more specific or we'll choose to order a cheaper bilge-rat to replace you."

    ~seanz

  2. #562
    Join Date
    Jan 2008
    Location
    Wow-Ming
    Posts
    16,516

    Default Re: Greenhouse Update

    Thanks! Here's a bit more on the temperature control setup.

    As you can see by comparing the indoor and outdoor temps, there are some broad temperature gradients involved.



    34.9F is a mild outdoor reading for midwinter. On a clear, cold day, it might be 5F outdoors and 90+ inside. There are thermally driven ceiling vents that I set to open just a crack, while usually block the intake vents.



    When the outside air is cold, a direct draft can damage or kill tomato plants. (The plant shown is a goji berry I started from a cutting.)

    Besides the Taylor digital thermometer, I have others to help me balance the heat—



    A soil probe thermometer shows the temperature of the main thermal mass, a rammed sand floor, 12' x 12' x 3' deep. I laid down a mat of reflectix slab insulation and 2" foamboard before filling it. The soil temp outdoors is around 10F, so the combination of direct solar input and heat from the flat-plate collector maintains the floor temp within a decent range for plant growth.

    The wired probes for the Taylor digital thingie quit working after a year or two underwater, so I went to a pet shop and got a cheap aquarium thermometer. The reflection obscures the 9: the water i the 400 gallon heatsink under the floor is 98.3F. I usually start pumping warm water through the floor when there's 20F difference in the temperatures.



    The one thing missing is a photo of the combination temperature/pressure gauge on the glycol loop that conveys heat from the flat plate collector through coils of PEX tubing to the water in the big heatsink. The pressure ranges from 10 psi up to 20 on sunny days, and the incoming fluid reads 100F up to 140F or so.

    All this is fairly automatic, so I don't have to dash out to the greenhouse every time the sun goes behind a cloud. The main thing that needs watching is when the flat-plate collector is clear, heating the lycol solution, while the 20W PV panel which drives the pump is covered with thick frost or snow. It's blown up twice under those conditions (popping the end of the PEX tubing out of a joint). The fix is to cover the collector, refit the tubing at the joint, recharge the loop (glycol and water) using a drill pump, and then start it up again.

    Worth the trouble, I reckon. Here's yesterday's pick—

    We're merely mammals. Let's misbehave! Cole Porter

  3. #563
    Join Date
    Jan 2008
    Location
    Wow-Ming
    Posts
    16,516

    Default Re: Greenhouse Update

    The strawberries have been looking sad, with reddish edges on the leaves, which eventually wither. I suspected a soil fungus, owing to wetness, so I lifted the plants, then scrubbed the pots and doused them with boiling water. They have built-in drip cups underneath, that hold water and keep the base of the pots damp. So I popped those off and put a gravel/sand mix in the bottom of each pot, for drainage. Then they they were refilled with new soil.



    The bed of greens is getting jungly. Maybe a good night for kale.
    We're merely mammals. Let's misbehave! Cole Porter

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