Modifying solar vent openers

I have 6 vents that are operated by solar vent openers on my greenhouse and I'm thinking I want to modify them to open the vents at higher temps. I'm growing mostly palms that like it hot. Out of the box, the vents start opening at around 75 and go fully open around 85 or so. I already use the hole in the motor stem that makes it work at higher temps. This makes it start opening later, but doesn't open as far as when you use the hole for cooler temps. I covered the solor "motors" with white paper hoping to make them work on ambient temp alone (as opposed to heating from the sun). That helped, but not much. I'd like the vents to only start opening in the 85-90 range and open all the way around 95 or so. After looking at the openers, I think I can drill new pivoting mounting holes closer to the fulcrum which should make the temp span "tighter" in which it goes from closed to open, but then I'll probably also have to drill another hole in the stem of the motor to allow it to expand more before it starts to open the vent. Anyone have any experience in this?

Stosh

Stosh
I had a GH when I lived in Rochester, NY. I kept me sane, and I am not kiddinng. Do not do winters well, hence the address of FL.

Anywho. I think that you have to adjust your thermastat, not change the "fulcrum, pivoting holes, etc. ???? I have no idea what you are taking about here.

Hap

BTW....Happy Birthday.....

This message was edited Jan 7, 2007 6:59 PM

Happy birthday! Sorry I can't help you out on how to make the changes...but I have to ask whether it's really worth all the trouble? If your palms are happy under your current conditions, I don't think the vents opening a little later is going to make them that much happier, and if they're not happy now I don't think that'll make the difference.

yes you'll have to drill both points but it will be dicey work the spacing of the holes is critical.

Ecrane3,
LOL how did you know?
As far as the palms being happy, the auto vent openers were working during the summer as they were meant - the 75-85 like I was talking about. The palms grew, but not like they could have been. During the fall, the nights were cool and I set the heater to 70 degrees. First thing that bothered me was that sometimes the air near the ground near the outside edge of my greenhouse was cooling faster than the air up in the top, so the heater would kick on while the vents were still open! The next thing that bothered me is I have lots of passive heating - water jugs, barrells, etc. I'd get excited when the bright sun would come in and before anything got a chance to warm up, the stupid vents would start opening - VERY frustrating. Later in the fall I decided to disconnect the vent openers and leave everything sealed up as tight as possible. I started to learn which days would get too hot - 105 or over. Those days I would come home for lunch to open the greenhouse door, or possibly leave it open in the morning. This got to be a serious pain. I was putting in a humidifying system from scratch anyway, so I decided to tie in a second thermostat. This second thermostat would kick on the humidifying (which also cools the air) when the temps got around 98. This did the trick for all but a small handful of days where the outside temps got really warm (like 70-80) plus strong sun. Now that it's winter, my greenhouse hits 90 regularly, but rarely 98. This spring, when the sun gets strong, but the mornings are still cold, the cooling from the humidifying system won't cut it.
Anyway, the palms are going crazy now. 70 degree nights plus up to 95 degree days when the sun's out plus plenty of himidity - they're growing better than in CA!

Happy1 - I went to school at RIT for 5 years. I know exactly what you mean about keeping you sane. I only live about 4.5 hours from there now, but it's like another world. Spring fever (or cabin fever) up there was for real. If I could find a way to make a living in southern FL, I'd leave tomorrow. I'm so jealous of your 10b. I love the heat. I love the humidity - especially with a swimming pool and a margarita nearby!

Well, the palms here seem to do just fine even though we almost never have 70 degree nights or humidity and not too many 95 degree days either! You must be growing the types of palms that do better in Florida, the Caribbean, etc, I could see that they would like those conditions!

Stosh,

Just think, down here you wouldn't need a greenhouse!!

Hap

Stosh, could you please let me know the size and model of your solar vent.
Also, about how much did it cost? I was considering a thermostaticaly controlled power vent,
but I would like to check out this type first.
Thanks, Dave

Dave,
The vent was built into the greenhouse. It is nothing more than a piece of twin wall polycarbonate on a hinge. The solar powered opener can be found here:
http://www.farmtek.com/farm/supplies/ProductDisplay?catalogId=10052&storeId=10001&langId=-1&division=FarmTek&productId=31805
There are a few different styles available. There isn't much adjustment available on them. Like I said in my posts, I wanted much warmer temperatures than the opener would allow.

Stosh, thanks for the link.
I like the fact that the solar ones dont use power, but with the powered ones
I think you have more control over the high temperature using a real thermostat.

Just a thought, Maybe wrap some insolation around or above the cyinders to delay heat build up from the sun ?

I'm pretty sure insulating is not what I want. That would really slow the response time on these already slow devices. But I do want to block direct heat from the sun. I already wrapped the solar cylinders with white paper which reflects the sun, but doesn't insulate too much. That didn't make enough difference. I'm going to try drilling. I'm sure that more elaborate controls have much more capability, but they also have much more price.

I have been growing in greenouses most of my life. But I have never had a green house in Florida, so I am not sure how helpful I can be. The sun is so much more powerful there than in the Northern states. I am going to assume that you are using a shade cloth. Couldn't you just go to a lighter shade cloth on the outside which would allow more light into you green house causing it to heat up faster? Another thought would be to cut your roof vent into smaller sections, perhaps three, one being larger in the center with two smaller ones on each side of the larger vent. Then you could disable a portion of them during cooler periods, and maybe only have one section opening and closing during most cool periods of the year, the one furthest from your heater. Another thought would be to close off all vents on the sides and doors which would decrease the positive air flow when the greenhouse starts to heat up.

You probably know this: using fans to circulate the air really helps to keep your air temperature even. You need at least two strong fans, one at each end of the greenhouse facing toward the farther side so as to loop the air around from one end to the other and back again, creating a positive air movement. You should be able to feel the breeze and the plants should move gently. When the heats on and the roof vent is open, the moving air will help to equal out any little micro climate areas that would normally be stagnant and be cooler or warmer than the rest of the house. On cooler days you could keep the roof vents closed and open up the wall vents and screen door which would allow fresh air in but not vent the green house much. Again, this is doable with strong air movement generated by fans. If your greenhouse is small you can probaby get away with 16 inch floor fans that you can buy cheap from hardware stores, usually under $25.00 each. These will last about 2 years with continual usage, and they don't cost too much to run. I use them and I like to buy them when they are on sale. I usually buy three or four at a time and just store them.

Patrick,
Those are all great general greenhouse suggestions. Thanks. But I'm who started the thread and I'm from Denver, PA (zone 6). You're not much further north than I am. No, I don't use shade cloths, except for the 3 months in the middle of the summer. I need every ounce of sunlight I can get!