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Denver, CO

Cant seem to find a fan that could be used in a small hoophouse to exhust air when the tempature rises above a certian threshold? Have built one myself but not sure if I can trust it to work well enough as its a complete cut and paste job. Any suggestions?

3/30/2007 10:10:44 PM

[email protected]

We use this louvered fan:

http://www.grainger.com/Grainger/wwg/itemDetailsRender.shtml?ItemId=1613608108

With this moisture resistant line voltage thermostat:

http://www.grainger.com/Grainger/wwg/itemDetailsRender.shtml?ItemId=1611632371

Works like a charm in a 16x8' greenhouse 8' tall.

Probably overkill for a small hoop house. If you go to greenhouse supply they offer a temperature controlled door opener that can be configured to open a venting panel.

3/30/2007 10:56:29 PM

Colo.Spgs.CO. Pikes Peak Chapter @ [email protected]

Greg, as long as you keep the humidity up, and a slight crack in the door of the hoophouse before you go to work your plants should be fine. It is when the humidity is very low without a cold frame is when you have to worry. Colorado has intense sun, and is basically a desert especially where I am at over 6000 Feet altitude. The ladder is always my worry. And also the direction of your hoop house is a big factor, east west is a no no your plants will cook, and also the clearer the plasic they will cook. 4 mil always cooks my plants, and I stick with the more foggy 6 mil facing more north south, and never have a problem until the house is removed and humidity gone. Just a word of experienced advice....Happy Growing

3/31/2007 4:14:16 AM

Ontario, Canada.

Would you consider an auto vent opener from Lee Valley

3/31/2007 1:09:40 PM

Ontario, Canada.

Controlling temperatures in a cold frame or greenhouse is straightforward with this automatic control.
It incorporates a gas-charged cylinder of adjustable volume. As the temperature rises, the gas expands; it will open a 15 lb window, more than adequate in cold frames and greenhouses. A simple adjustment lets you control the operating range. As temperatures fluctuate, the 12-1/2" long unit will open and close a window as necessary to prevent disasters.

Here is the link.

http://www.leevalley.com/garden/page.aspx?c=2&cat=2,43224&p=10543

3/31/2007 1:10:42 PM

[email protected]

Russ posted a link to the same mechanical opener that I bought a couple years ago. While I've never installed it in a cloche, I can vouch for the fact it opens as advertised. pretty slick little unit & probably all you'll need in a small hoop house.

Of course a box cutter & some duct tape works too but requires a bit more effort.

3/31/2007 6:21:28 PM

Waitakere New Zealand

if you use a fan to control temp in a plastic house just watch the humidity. the moving air will suck all the moisture out of the house and your plants will just transpire water trying to keep turgid

4/1/2007 3:37:02 AM

Denver, CO

Thanks guys, I will look into these options and see what I can come up with.

4/1/2007 10:18:18 PM

[email protected]

The $45 thermostat that I posted will run any 110VAC powered item. So even a small window fan can be set to turn on. Perhaps even several small fans in multiple cloches if a few extension cords are employed. Not cheap, but they work great.

4/2/2007 7:36:03 AM

Omaha, NE (N41-15-42 )

Yes, I have one of those vent openers that russ talks about. There's a pic of it from the outside in my diary. I got the automatic vent opener at Charlie's Greenhouse.

4/2/2007 10:38:44 AM

Eugene, OR

Considering the cost of just one of those thermostats, I've got one word....PLC (or is that 3 words LOL). Programming them is something anyone can do intuitively using if-then-else-and ladder logic. A much more flexible solution and in most cases, you can control 6-8 individual AC loads. http://web3.automationdirect.com/adc/Shopping/Catalog/PLC_Hardware

Just thought I'd throw it out there....

4/2/2007 12:18:26 PM

Denver, CO

Maybe I am looking at somthing to cheaply. The unit I built consist of three resistors, a thermistor and a relay and a small 4 inch 12volt fan, all ran from a 9 volt battery. In total, it cost about $4.50. If I had any clue about building electronics, I am sure I could trust it, but since I am a complete hack, I cant.

4/2/2007 11:06:24 PM

Eugene, OR

Interesting circuit. Are you using a positive or negative thermistor? It sounds like you're using a negative thermistor to control the current to the relay coil. When the temperature gets high enough, the current flow increases enough to trip the NO relay, engaging the fan.

Did you have to play with the resistor values to get the relay to kick at the temp. you wanted? Pretty ingenious!

4/3/2007 1:35:01 PM

Denver, CO

BrianinOregon,
Email me a [email protected] and I will send you the schematic and tell you what I did. Or anyone else who is intrested as well.

4/5/2007 8:04:01 PM