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Greenhouse construction

Discussion in 'Growing Areas' started by mrbreeze, Aug 2, 2012.

  1. mrbreeze

    mrbreeze Anglican Supporting Member

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    Let's hope so! Pathetic as it is...i'm still 'in process'. There is now electricity and the inside has been painted bright white and the cedar beams have been sealed. I did buy the heater which is currently sitting in my living room. Hopefully i'll get it hooked up this weekend.

    The last few things that remain to be done are: some caulking here and there, installing the heater, and figuring out the watering situation. But i'll probably start moving in shelves and plants while figuring out the watering. So i'm close. Stay tuned.

    Here's an interesting issue that came up. I had two vents installed with motorized openers which are controlled by a thermostat. The thermostat has a range of something like 40 degrees up to 100 or more. Since there is no heater yet, when it got cold the thermostat would trigger the vents to open. That wouldn't really be such a big deal since there are no plants in there yet. But....one of the motors seems to be jacked up in some way (that i can't figure out) such that when it starts opening the vent it just keeps running endlessly until the temperature gets high enough to trigger the thermostat again. And that can be days on end. So the motor basically has spent the better part of the last month running almost continuously. I'm literally shocked that it hasn't burnt out (last time i checked). I guess the morale to the story is either ...don't install things that are controlled by a thermostat until you can maintain a stable temperature, or, those motors are pieces of crap! Or both.
     
  2. KellyW

    KellyW Orchid wonk Staff Member Supporting Member

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    Since there is no heater yet, when it got cold the thermostat would trigger the vents to open.

    Shouldn't the vents open when it gets hot and close when it is cold. Unless you wrote that wrong I think something is installed wrong which may also account for the motor running all the time. Maybe I just misunderstand what you are saying(?)
     
  3. Alexey

    Alexey Well-Known Member Supporting Member

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    Looks like this summer I am beginning my GH construction adventure. I was already advised by several growers never use passive (heat driven) vent openers. Can you also advise which brand of motorized opener is better not to buy?

    BTW, what kind of heater will be in your GH? Thanks.
     
  4. msaar

    msaar Member

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    Think about how these things operate: when operation is called for (heating or cooling), the thermostat closes, providing current to the device (in this case the shutter motors) until the the set point is satisfied and the thermostat contacts open. Current is applied to the motors as long as opening is called for. Probably the only difference between your two motors is that one is noisy and the other isn't. The motors are closed under spring tension until current is applied and they operate against the spring tension until the current is removed. This is the way simple analog controls operate. If you don't need the vents to operate now, turn of that circuit.
     
  5. Marni

    Marni Well-Known Member Staff Member Supporting Member

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    I suspect that there are quite a few who would advise passive vent openers over electric if you ask around. I am certainly one of those. Congratulations of the coming greenhouse.
     
  6. mrbreeze

    mrbreeze Anglican Supporting Member

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    The heater is a Southern Burner non-vented type. The factory is just about 45 minutes from my house which was quite convenient.

    The motors are made by Multiproducts. I bought them from either Growers Supply or Greenhouse megastore. I don't think the motor running all the time is necessarily the fault of the motor itself but rather the fact that i don't have a heater going yet so the ambient temperature can fall below ~40 degrees, which is the lowest set point on the thermostat. Under 'normal' conditions, say when it is hot outside, I would have the thermostat set on around 70 and the motors would click on at that temperature and open the vents. In retrospect I should have had an on/off switch installed when I had the thermostat wired in. And I can't close the circuit because it is one of the circuits that runs part of my house.

    The real problem with the motors is that they operate by turning a spindle to which is attached an arm. The way the arm attaches to the spindle makes it impossible (illogical?) for the arm to actuate without running into the housing on the motor on the downswing. And the instructions specifically say to ensure that the arm does not hit that part of the motor. It looks like it was specifically designed for the motor housing to limit the movement of the arm so that it will swing in an arc just enough to open the vents and then stop. But that would be in complete disagreement with the instructions. So either the instructions are crap (clearly true), or the motors are not designed properly (possibly also true). The only way to install the arm on the spindle in agreement with the instructions would be if the spindle was about an inch longer. As it is, installing the arm so that it does not impinge on the housing requires you to attach the arm to the last millimeter or two of the spindle, and that makes the arm unstable.

    In addition to all that (which probably makes no sense unless you can actually see it installed and/or view a diagram of the way the motor works), the first motor that arrived had crimped wires and one of the wires was actually cut through. Lastly, the electrician said that the wires were not long enough and had to install a junction box underneath each motor. Long story short ....i do *not* recommend using this type of motor for vent opening.
     
  7. T. migratoris

    T. migratoris Active Member

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    Did you (can you) install the arm so that the attached collar is oriented toward the inside, rather than the outside? That made the difference for me as it pushed the arm away from the jog in the housing. See attached pic.

    GH 015.jpg
     
  8. Magnus A

    Magnus A Ph.D.

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    A thermostat does not normally work in that way. A thermostat has a "heat controlled switch" that is either open or closed, give signal or not. The switch deforms at a set temperature and does not have two set points in the way you describe it. I think you should check that thermostat and see if it not is set to give a signal below a certain temperature!
    The operation temperature only defines in which temperature range the company has tested it´s function. I would be surprised that a switch that should not give a signal under a set point suddenly does just that if the temperature drops below the operational temperature. That kind of devise is not safe and would never be allowed on the European market !

    IF you have one thermostat connected to both motors and only one runs continuously while the other is not, you do not have a thermostat problem! One thermostat that run two engine will NOT only run one if the electricity is connected in the right way! In that case you have an electricity problem I do not understand, or the motor that is not running is broken.

    /M
     
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  9. mrbreeze

    mrbreeze Anglican Supporting Member

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    It is not easy to explain.

    The thermostat has a range of about 40 degrees F. up to around 100 degrees. If I set it on around 70 or so, the vents will open when that temperature is reached. Since I really don't want the vents to open at this time of year, i turned the dial on the thermostat to its lowest setting. But that means when that (low) temperature is reached, the vents open. And when the temperature stays at that low temp., or goes lower, the motor keeps running on one vent until it warms up hotter than the set point, which was days on end a few weeks ago when it was cold.

    Now that it is warm again, the temperature is not going lower than the lowest set point and so the vents are not opening/motors are not running.

    Robin posted a pic of the same type of motors so you can see the arm attached to the spindle that i was talking about. His are installed upside down. I would say that's a sign that something is 'trouble' when you have to install it upside down. :p
     
  10. msaar

    msaar Member

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    There is no "correct" up or down. If the motor housing is interfering with the arm, consider re-orienting the motor. The operator is designed for use with many different shutters, and the motor should be installed so the assembly works correctly. Some shutters will have the actuator on top, some on the bottom. The motor in the photo could work just as well in a horizontal position.
    As for the thermostat operation, assuming 1) i t is intended for cooling operation and 2) it is single stage thermostat, it should close on reaching the set point on a rise in temperature. If it closes on a fall in temperature (as yours seems to be), consider that it might be wired for heating rather than cooling. On a warm, sunny day (which we had today), when the temp in the greenhouse is above 40, move the set point until the vents change position to ensure that they are opening on a rise in temp.
    The operation you describe seems to be for heating.
     
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  11. Magnus A

    Magnus A Ph.D.

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    I agree with msaar on your thermostat issue! What you say above does not make sense.

    A thermostat that opens vents above a set point does not reversed it´s function if the set point is below ambient temperature. It should still open the vents above the set point, at all settings.


    IF your the thermostat is working for cooling:
    If you do not want the thermostat to open the vents you should set the temperature as high as possibly! If you set it to 40 the vents will be open as long as the temperature in the greenhouse is ABOVE 40 !
    You do not want to open the vents in the winter and this is excactly what you do if you set your thermostate to 40! When the temperature raise above 40 the thermostat give a signal to open the vents.