Forum home› Garden design
This Forum will close on Wednesday 27 March, 2024. Please refer to the announcement on the Discussions page for further detail.

Automatic greenhouse vent openers

michellellewmichellellew Posts: 26
in Garden design
Have 3 openers in greenhouse that don’t appear to work, only recently moved so don’t know about last summer. Husband has oiled them so at least windows can now at least be raised but should I be able to move/twist black cylinder? thought that was how to set temperature. These look like they haven’t moved for some time. Any advice and thoughts greatly appreciated 

Posts

  • fidgetbonesfidgetbones Posts: 17,618
    I find that they have a limited life. The black barrels seem to leak the contents eventually.  You should be able to twist a knob on the end of the cylinder to adjust the temperature at which the window opens.  If you can't maybe it is time for some new ones.  Bayliss autovents are the usual ones, they have two year guarantee. Their web site may help you more.
  • KiliKili Posts: 1,104
    edited March 2020
    Hi, my understanding is that most are filled with wax. When the temperature rises the wax melts and expands in the cylinder to push the rod out and open the window.

    Most of these only work at approx 20 degrees, therefore at the moment they wont open
    automatically unless the temperature in your greenhouse reaches that temperature or thereabouts.

    I had my greenhouse door shut and we had some good sunshine where I am today and two of my four opened for the first time in 5 months because the temperature got up to 20 or above inside the greenhouse which allowed the wax in the cylinders to partially melt and expand enough to auto open them about 4 inches.

    There's likely nothing wrong with them its just the temperature is not high enough to melt the wax in the piston/rod. If the wax is solid I dont think you can turn/twist the cylinder to open them but, I'm not sure on that one so you may need to check online.

    If you want to test one take it out and drop it in a bucket of hot water and you should see the piston push the arm out when the wax turns from solid to liquid/expands.

    Stick it in the fridge if you want it to close again as the wax will harden and contract.

    Kili

    'The power of accurate observation .... is commonly called cynicism by those that have not got it.

    George Bernard Shaw'

Sign In or Register to comment.