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2007 Greenhouse Solar Fan

How we installed the Harbor Freight Solar Fan

***Requisite Disclaimer:***

I am posting this info to show how we assembled my greenhouse - in the hopes that someone else might find it helpful.

We are not Construction Professionals (which *should* be fairly obvious!), so this is not intended to be taken as "Gospel!" Use whatever info you find useful, but if you're in doubt, PLEASE consult a professional! And check your local building codes, etc. etc. before proceeding. I am not responsible for any errors, damage or injury that may occur as a result of following our "Totally Unprofessional Advice" (Remember, we were being supervised by a Dachshund!:-)

Update 08/30/07:

My website is fixed now (Yayyyy!!!). For the record: Freeservers ROCKS! :-)

So anyway, this is a Continuation of the Continuation of the Greenhouse Saga of 2007. I'll continue posting updates (As they occur or "When I have time!").

Solar Fan:

The latest addition (08/26/07) is the Harbor Freight Solar Fan. That was my Anniversary Gift from Rog. It comes with two 'very large' Solar Panels, a bracket to hold them, a controller, and a fan that's rated at 251 CFM which, I believe, should *just* be sufficient for my 6x8 GH. I don't remember the specifics, but I recall that I researched this awhile back (there are many webpages devoted to stuff like this, and plenty of info to be gleaned from Gardenweb as well). I believe the fan is appropriately sized for my GH (and if not, I welcome feedback!).

(I got feedback. See below. The fan is undersized :-( Oh, well!)

We had some 'challenges' with setting this up, however. The first being "Where the heck are we gonna put these panels???" Any south-facing real-estate on the roof is already spoken for (We have solar heating for the pool). What few open spaces we could find were a LOOOONG ways away from the GH. Rog wanted to put it on the roof of the GH, but I didn't want to block precious sun (in the wintertime, anyway!). We ended up rigging it up on the fence, behind/next-to the GH. We found a sturdy corner where 2 fences meet (w/2 4x4 PT studs) and built a shelf for the new Solar Panels.

Even though it's right next to the GH, the supplied wires were too short, so I bought 14ga "Outdoor" wire so we could run the lines into the GH. I'd purchased 20' of flexible conduit and, even though the wire itself was very stiff, we just couldn't get it to go thru the conduit. Hence the rather 'inelegant' PVC pipe running down from the shelf. The PVC continues 'under' the GH and is mainly intended to protect the wire from the elements (and weenie dog puppies who like to chew!)

Roger pretty much took ownership of the entire Solar setup. And I think he did a damned fine job!!!

Pictures/notes below. Click on the thumbnail to see a full-sized version.....................


View of Solar Panels as seen when standing at the front of the greenhouse. Note: The PT vertical 2x4 is supporting the shelf. The crooked-looking PVC pipe (which I'll probably paint dark brown so it blends in) is just covering the wires and not "supporting" anything...

Closer view of panels. The bracket that came with the kit from HF seemed kind of flimsy at first, but it's actually quite sturdy.

The panels themselves are facing kinda ESE in this shot - we couldn't rig them for a due-south orientation, unfortunately (08/30 Update: We have since moved them so they're facing more SSE)...



The control panel is attached (using a t-bolt) to one of the fwd wall-studs.

Note: Exposed wires on control panel = BAD. This will need to be covered up before the rainy season (or, most likely, eliminated entirely when winter hits)


And we've hooked it (Temporarily) to a Deep Cycle Marine battery. I'll be looking into smaller 20+AH Photo Voltaic batteries for a more permanent solution. As it turns out, the fan *does* need the battery in order to keep running thru the afternoon (sun gets pretty low in the sky).

Note: The battery box is closed now. No exposed terminals anymore :-)


View of fan from the exterior. Again, not terribly elegant, but it works! (I'll put a neater 'circle' of aluminum tape around the 'front' side of the fan, at some point, so it'll look nicer!)

We cut a triangle of thick acrylic and used the 'over-the-door' piece as a template. We then cut a circle for the air to flow outward using a jigsaw (Important Note: Use Skilsaw Lubicant on the blade when cutting thru acrylic - otherwise it'll melt back onto itself!)



View from the inside. In anticipation of bug-proofing the GH, I cut a piece of window-screen and used aluminum tape to stick it down around the fan, then we bolted the fan in - sandwiching the screen between the fan and acrylic.

(Add'l observation added 09/16/07: Might not be a bad idea to tape some window screen to the "inside the greenhouse" side of the fan. GH hasn't been entirely bug-proof this past several weeks and I see a LOT of dead bugs squished on the "in" side of the screen [inside of the fan] where the fan has attempted to blow 'em out. It's pretty gross!!! ;-)

In this pic, you can also kind of see the galvanized ground wire that Roger installed (LH side of the fan). We've got that running down to the ground, and it's attached to a 2' length of rebar that's been driven into the ground.

* * * * * * * * * * * * *

Well, the fan has been in for one whole day. The fan itself seems powerful enough, and seems to run "mostly" off of the solar panels. And in the morning, before the greenhouse heats up, the solar power is diverted to the battery, so it seems to keep it "topped off" sufficiently. I'll post more updates on solar-power performance as the seasons change.

Right now, the gh remains insanely hot because the fan is just drawing hot air from the open ceiling vents, and out thru the front. I need to add passive intake vents on the bottom back wall - and probably consider closing the ceiling vents to see if I can't encourage some "sucking" of cooler air from the bottom back-side of the GH and then exhaust the hot air from the top/front. This is going to be a challenge, I'm sure!!! Once again, stay tuned for updates!



08/30/07 More Updates: "We're havin' a Heat Wave!" Temps are hitting triple-digits now, so this *probably* isn't the best time for Experimentation in Temperature Regulation! Oh, well!

I added 60% Shade Cloth (pics coming later) to the entire south-side, entire roof, and 3/4 of the [east-facing] front of the GH. I removed the self-opening mechanism from the vent. I also drilled 6 x 3" round holes in the 2x12 along the back-side of the base.

Theory being: I need to encourage air-flow. Cooler air from the bottom back-side would get sucked in and blown out thru the upper, hot side of the GH by the fan...

Well, I have since learned (from a GardenWebber - and confirmed by a couple of web-sites that specialize in this sorta thing) that 251 CFM is not sufficient for cooling the GH (Ooooops!).

Updates 09/16/07:

Ad"Vent"ures in Ventilation!!


08/30/07 Additional Observations: Optimally, an exhaust fan should poop-out the equivalent of ALL of the air in the GH, per minute. If you can maintain that level of exhaust, the GH will be appx 8* above ambient - in hot weather.

Rog loves math (I hate it, but I *can* at least balance my checkbook!). We have determined that the GH has a total of 292 cubic feet (there are online calculators out there - just Google "Greenhouse Ventilation Calculator" and you'll get tons of hits). Well, @ 251 CFM, we are running at appx 85% efficiency. Not sure exactly how that equates, theoretically. But in "reality" it seems to work out to 20* above ambient.

Outside temps have been hovering in the triple-digits, of late, and the GH hit 122* today (Ouch!!!!).

I'm still experimenting, but I'm mighty glad I don't have any plants in there now!!!

I'll keep 'tweaking' it and post the results of my findings...

Shade Cloth on south side and entire top of GH. I'd hoped this would help bring the interior temperature down (25* + over ambient, even with the vents open *and* the Solar Fan). It probably brought it down approx 5* (not nearly enough). With the addition of the shade cloth, I had to eliminate the self-opener on the roof vents. Probably just as well b/c the fan was only drawing hot air from the roof vent and blowing it out the front. I needed more cross-ventilation.

I thought I was being ingenious, drilling a series of 3" round vent holes across the bottom, backside of the GH. Theory being cooler, bottom air would be sucked in thru the back and hotter air would blow out the top.

And the ingenious part was thinking I could use these round vent covers (from Home Depot) during warm weather, and replace 'em with the "plugs" come wintertime (after wrapping weather-stripping around them, of course)...

Results were less than satisfactory, however. GH was still >20* above ambient during the day (We're talkin': Triple-Digits, consistently - even when outside temps were in the low 80's)

Some Garden-webbers build screen panels to replace the polycarb panels during the summer. I wasn't feeling quite that industrious, but I didn't see any reason why I couldn't simply tape screening to the aluminum frame *under* where a panel would go. I decided to do that to one of the north side panels (toward the back). It's in a fairly protected corner of the yard (right next to a fence), so wind shouldn't be an issue (Inquisitive weenie dogs... Well that's an entirely separate issue!).

I used aluminum tape to stick it directly to the framework of the GH (taped it on the inside and outside). It ain't exactly "pretty" but I'm okay with "functional" at this point. Besides, this is going to be behind my shelving unit, so I'm hoping it won't be glaringly obvious!

I did have to partially disassemble the GH so I could tape the screen *under* one of the diagonal supports - but not a huge deal...

Here's an inside view...

I wouldn't recommend doing this to too many panels (IMHO). Like I'd mentioned, some Garden-webbers build actual screen panels to use during the summer. I presume they're building some kind of "legit" framework around the screen. See, the polycarb panels *do* add rigidity and strength to the structure. I'm hoping the removal of one panel won't have any detrimental effects, but I think if you tried to do this to several panels, you might run into issues...

Also, I'm not entirely sure that aluminum tape was the best material for this application, but I'm willing to give it a shot... Time will tell!

And a close-up shot, showing how I ran the tape under the diagonal support beam. (Did I mention that "it ain't pretty?!!" Oh, well!) As of today (pretty bright 'n sunny), the GH seems to be more like 15-18* above ambient. This *seems* to be an improvement (not as much as I'd like, but...).

Experimentation will continue.......... ;-)

Added 10/08/07: Box Fan + Cool-air Humidifier (Plus Boom-Box - I gotta have my Jimmy Buffett!!!)

Doesn't it *look* positively idyllic though?!! ;-)

Note: Box Fan and Humidifier will be removed for winter. These are not suitable for use in wet environments (besides, I'll need the shelf-space!)

Update 10/08/07: More Ad"Vent"ures in Ventilation (And Heating)!

I found a cool-air humidifier on eBay for cheap. It's a Duracraft DH-805 (assuming you can even still buy them!). It's basically a 3 gallon basin, filled with water. Air gets sucked in, from the side, and is drawn over the water basin. Then there's a fan on top that blows the cool, moistened air upward. I've set it in front of a box fan. Everything is plugged into a temperature-regulated Thermo-Cube outlet that turns on at appx 78*F.

This is my electrical supply. It's an outdoor-rated extension cord (hooked up to a GFCI outlet at the pool equip't appx 3' away). It has an add'l built-in GFCI, so I think I'm pretty safe. Worst case, if it gets really wet in the GH, I'll slip a zip-lock baggie over it (still better than the "Electrician's Nightmare" I was running in the tent GH last year!!!)

Note: This is the summertime setup (when everything is bone-dry). I'll have to rig up something different for when the rains begin.

Since I've installed this, nighttime temps have been dipping into the 40's (and the GH stays consistently 2-3* above ambient @ night), so I've left the GH completely closed. Daytime temps have stayed within 15* of ambient - in spite of the fact that everything is closed up! Of course, the sun is pretty low in the sky now, so summertime wouldn't be very nice. Nevertheless, I haven't topped triple-digits in the GH since I set it up!

Another eBay Acquisition: A "legitimate" (and waterproof!) thermostatically controlled outlet. You can buy these at greenhouse suppliers, but I'm happy with this one (b/c it comes w/instructions so you can use it either as a Hot or Cold thermostat, by simply reconfiguring one wire inside the unit). Anyway, this one is set to turn on @ appx 40-42*F and I've got it hooked to my heater (that hasn't kicked on - YET!).

BTW - Yes, I know it's hanging upside-down!

Yet ANOTHER eBay Acquisition (I should buy stock, huh?!!).

(Don't laugh, okay?!! ) This is a "Desa" Umbrella-Stand Heater that puts out about 5,000 BTU's. It's 1500W, runs on AC and I haven't calculated how many BTU's I actually "need" (nor how much it costs to run!) - but I used this in my (much larger, much wetter) "tent" GH last year, and I didn't experience any fatalities. So I'm reasonably confident that it will work in my 6x8 HFGH!

It's not like I'm trying to maintain a "specific" temperature-range in my greenhouse. I'm basically just trying to keep "marginal" plants alive thru the winter (I'm okay with "survival" - I'm not necessarily looking for them to "thrive" - Brutal, but true)!!

I also plan to rig a string of red X-Mas lights - behind the thermostatically-controlled circuit, so I can look out the window to see if it's on. I do have a wireless weather-station, so I can monitor the GH temps from the comfort of my bathroom :-)

Stay tuned, I'm sure there's more to come in the weeks ahead (Friggin' Winter-Weather is already starting out here! Grrrrrrr!!!)



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