Hey everyone. So I've been fighting this thing for a few weeks now but I think I finally got it whooped. Still a lot of finish work to do, build a control panel for all the sensors and such, wire management etc. but the system is fully redesigned, reworked and working. Literally TOO well. I kinda put a Ferrari motor on a smart car with this system, but when I double or even triple the size of the enclosure this thing will manage the temps just fine I'm sure, as it is currently maintaining any temp I choose as well as providing any nighttime temp drop I can imagine needing. I'm sure it has limits however I do not yet know what they are. Summer will tell I'm sure.
I'll try to make this as brief as possible, but I'm horrible at that. Also it seems like there's quite a few folks interested in the subject of cooling and since I haven't been able to locate anyone using the same technique I thought I would provide as much info and pictures as possible since it's easier than one might think and really quite effective.
Prior to being completely overhauled the original mini fridge worked flawlessly in my absence from September of 2016 to December 2017! Keeping daytime temps around 78-80 most of the time and of course a little warmer and it struggled some on hot days. Nighttime temp drops suffered a bit on these occasions but no other complaints. Nights were 55-58 regularly (dependent upon number of daytime operations) and frequently hit 51.
Finally a few weeks ago it never got below 62. This went on for a few nights, then it only got to 63. This simply wouldn't due. I figured it was probably SUPER frosted up in there since it's constantly pulling in 90-100% RH air. So I knew this was coming and honestly I was shocked it lasted this long. One of the MAJOR flaws with my design is that in order to remove the fridge I have to disassemble it from the wall of the enclosure. This entails moving the enclosure etc. Essentially a triple black diamond pain in the...you get the idea. I'm just glad I built the thing on wheels. Like I said, I knew this was coming. Still, rolling the thing around is nerve wracking. I'm picturing plants falling over, cords getting tangled or cut etc., or the nightmarish vision of the whole business teetering over like a bakers rack on an episode of
I love Lucy. The point is I only wanted to do this once. I would have to disassemble it to the same extent to defrost it as I would to completely replace it. I decided to replace it. I finally found a FREEZER that I THOUGHT was the same size. The online description said 1.1 cubic foot but I figured it was a typo as all other similar models were 1.7 as my current one however they were ALL refrigerators with the tiny little single serving freezer part. The only full freezer was the one I ordered. It arrived. It was not a typo. It was a mirco. It doesn't sound like too big of a difference right? Refer 1.7 vs. freezer 1.1? Should work at least as well, if not better right? I didn't want to wait for returns and finding a new unit, waiting for shipping etc. so I put it in. After a week of waiting for it to fully freeze (I have it wired into a temperature controller) and give me the drops I'm looking for I throw in the towel. I found a 3.5 cubic foot chest freezer that was short enough that I could fairly easily run ducting in and out of the top of the freezer and to to/from the enclosure. It's also at Best Buy and shockingly NOT an online only item so I can just go grab it. I do. While there I see only the 5.5 model on display. It's the same height and depth, just 6 inches wider and 20$ more. I leave with that one. Now I just need a bigger fan, some duct etc. I'll list what I used as well as a few pictures of the steps. It's currently set up to only allow the fan to circulate air if the temperature in the freezer is within a certain threshold. This way the system only operates long enough to provide a few degrees of cooling then disengages to allow the freezer to catch up as well as providing a more gradual temp drop at night rather than 20-30 degrees in less than an hour. It also prevents the system from depleting it's cold reserve during daytime operations. Lastly it minimizes defrosting and won't allow it to run all night chasing the last degree or two of temp drop, meanwhile barfing several gallons of ice cold water all over everywhere.
THEORETICALLY. Oh and I was also concerned with the air being too cold, but I haven't encountered that yet.
The components are:
1 - "Insignia" 5.5 cubic foot chest freezer from Best Buy.
1 - "Active Air" 6 inch 400 cfm inline duct fan. [I wanted the 4" 190 cfm but it was out of stock.]
1 - "Ideal Air" fan speed controller. MANDATORY with the 6 inch fan, highly recommended with the 4 inch. Fan and controller from local Hydroponics supplier
* Mine is currently running at just over minimum.
1 - "Ink Bird" STC-1000 temperature controller. [This is used to ensure system only operates if freezer is cold enough.]
*In hindsight I would use the ITC-1000 model as it is a Fahrenheit unit. STC-1000 is Celsius. Both on Amazon.
1 - "Sentinel" BTC-1a Temperature controller. This is the daytime nighttime thermostat. (Amazon)
*currently looking for an alternative as this model does not display current measured temps. Also seems to be losing accuracy. Does not go below 51 degrees. Daytime/nighttime function determined by photo cell, so it must be mounted in the grow area to work correctly. There's a host of inconveniences honestly. Alternatives are expensive however. This unit is under 100$ (best unit by far at this price point), most others are approaching 200$. It has worked well for over a year in nearly constant 99% RH, so it's a great place to start.
1 - 3 prong grounded UL listed 15 surge protector. (Home Depot)
1 - 10 foot stick of 4 inch HDPE drain pipe. (Lowes)
6 - 4 inch by 90 degree HDPE drain pipe "street 90". The other option is "elbow 90". "Street" 90s have a shorter radius than "elbows" allowing for a tighter turn in smaller spaces. I used the "street" type in all of the offsets to achieve a more compact duct run. I also purchased 4 - 22 degree segments and 4 - 45 degree segments as well as several couplings. (Lowes)
I wasn't entirely sure of my duct route and I wanted to have some options. I ended up using all of the 90s and 22s and most of the couplings, but not the 45s. A couple tips for purchasing duct/conduit etc. -be sure to PHYSICALLY check that all the pieces fit together tightly. This seems like a nobrainer but just because it says 4 inch doesn't mean it will fit other parts that say 4 inch. 4 inch HDPE drain pipe fittings won't work with 4 inch PVC schedule 40 conduit for example. Also, when planning an offset know that you will need two of the same degree of bends for each offset. It would be much easier and cheaper to use flexible insulated duct however there are several problems with this, the primary issue being moisture/water. You will have condensation in the duct. The rigid plastic duct allows you to plumb it in such a way that the fan is at the highest point in the system and all the duct work leading to and from can be given a slight grade to allow for drainage back into either the freezer or the enclosure. I believe any of the flexible stuff would rapidly deteriorate into a soggy, sagging dripping, moldy mess in no time.
3 - R6 6 inch or smaller duct insulation sleeves. (Home Depot)
3 - Rolls 3M "Aluminium Metal Repair Tape" 1.88 inch x 50 yards. (Lowes)
1 - R-Tech R7 "Insulfoam" panel 1 inch by 8 foot by 4 foot. (Home Depot) This is for the lids and baffles of the freezer. It is Aluminium foil on one side and very thin plastic film on the other. Every panel I cut I covered with a layer of the 3M Aluminium tape everywhere except where it already had it. This is more for water/moisture protection and because ice seems to stick to the porous Styrofoam MUCH better than the smooth aluminium. You'll want to use a large carpenters square or similar straight edge to keep your cuts accurate and square. Use a serrated blade. A razor knife is a disaster. I used a kitchen steak knife.
I wanted to take more pictures for more of a step by step but I was pressed for time as I wanted to complete the installation with enough time to give the freezer a head start on the nighttime temp drop. For this reason I did the build in two stages. The first was install the fan and ducting on the back of the enclosure and insulate it. Then re position the enclosure where it goes and install the remaining duct work and freezer lids. A couple days later I disconnected the duct at the freezer and insulated the ducts, installed the baffles and thermal mass in the freezer and buttoned it back up. I did not use any glue at any point. I don't want the chemical exposure to the plants and I want to be able to disassemble the duct easily for repairs or modifications. For example I'm going to be taking it apart very soon to install some sort of a splitter just before the fan and another just before the enclosure so that I can use the fan at full force to defrost the freezer without affecting the environment in the enclosure. I just haven't found the right fittings yet. Anyhow, here's the pictures.
The freezer and fan with 6" to 4" reducer and 4" 90 dryfite.jpg (1.91 MiB) Viewed 8528 times
Fan installed where mini fridge/freezer were. It' a BEAST! WAY overkill! That small opening is where the pipe for the old unit supplied cold air. I ended up reusing this opening and pipe and just sleeving the 90 over it. theheartbeate.jpg (3.27 MiB) Viewed 8528 times
The warm air return duct. warmreturninsulatede.jpg (1.6 MiB) Viewed 8528 times
Warm air return warmreturnintakee.jpg (2.84 MiB) Viewed 8528 times
Just one baffle for now. Notice the hole at the bottom. This is on the opposite side of the freezer from where the air is coming in. Just a quick way to slow the air down a bit for the first night. firstbafflee.jpg (2.4 MiB) Viewed 8528 times
Supply and Return duct work complete. This was the stopping point of the first phase. pipingandfreezere.jpg (3.4 MiB) Viewed 8528 times
Side view of same returnandsupplypipinge.jpg (1.99 MiB) Viewed 8528 times
This was the stopping point for the first phase. The following pictures start somewhere near the middle of the second phase.
Here the baffles are complete. These are just the foam insulation all tapped up with the aluminium tape. For the most part it's just friction from the tight fit holding it together. there's a little tape to keep things square and plumb and somewhat air tight. The frost will do the rest. Nothing is tapped to the freezer itself to allow for servicing. bafflescompletesidee.jpg (2.68 MiB) Viewed 8528 times
Same as above, top view. bafflescompletetope.jpg (2.68 MiB) Viewed 8528 times
When cutting the baffles I accounted for a dual lid set up. the first lid fits fairly snugly INTO the opening of the freezer. This also sits flush with the top two of the baffles, and the center divider. The other two baffles sit flush to the BOTTOM of the freezer and has a gap at the top for air flow. The other two baffles have the gap at the bottom. This forces the air to travel into the freezer, up to the first gap and down to the next and so on ultimately zigzagging up and down repeatedly before re entering the enclosure. The second lid fits OVER the opening to the freezer just like the factory lid. The gap between the two lids is bridged by couplings thoroughly tapped to the upper lid and rather tightly fit into the bottom lid so that they stick out of the bottom a little. There is a short diagonal cut piece of duct on the other end of the coupling to help push the air down over the frozen bottles in the first and last compartments. Again nothing is glued for serviceability and the diagonal cut is to allow for frost build up without blocking air flow.
Diagonal cut downpipe and coupling. downpipee.jpg (3.24 MiB) Viewed 8528 times
Some soda cans 3/4 full of water to accommodate freezing. Stacked 3 high. This is for thermal mass - something frozen to slow and cool the air down. Positioned sparsely to allow for frost buildup without blocking air flow. Hopefully. bafflesfulle.jpg (2.34 MiB) Viewed 8528 times
Inner lid. The edges and the opening for the down pipe all carefully aluminium tapped up to help reinforce and protect it. Don't forget to make a little hole and install the temperature probe! innerlide.jpg (3.15 MiB) Viewed 8528 times
All buttoned up! Still lots of finish work to do, but it's complete mechanically. almostdonefronte.jpg (1.88 MiB) Viewed 8528 times
Side view. almostdonesidee.jpg (2.6 MiB) Viewed 8528 times
Electrical connections:
The surge protector is connected to the output of the daytime/nighttime thermostat as before. The ITC-1000 is plugged into the surge protector. The "HEATING" output of the ITC supplies the power to the fan controller which then supplies the fan. I know that sounds counter intuitive, but it works much better than if connected to the "cooling" output. The sequence goes like this; The thermostat energizes the ITC. Essentially this is a "cool request" to the freezer. If the temp probe of the ITC is below -6.8 C or 19.7 F, it completes the circuit to the fan via internal relay. The fan will operate until the internal temp of the freezer WARMS up to 3.3 C or 37.9 F OR the end of the cool request from the thermostat, whichever happens first. If the cooling output is used, the fan will run full time and the temps inside the freezer will continue to warm ultimately resulting the surprise living room water works attraction mentioned earlier. I'm currently searching for a better controller for the enclosure, ideally something with multiple daytime and nighttime settings for more gradual, accurate and natural changes. For now I'm getting a daytime high of 76 or so and nighttime lows between 50.8 and 53.5 F. The nighttime temp is restricted by the thermostats 51 degree limit and not the cooling capacity of the system itself. It currently runs for about 30 to 40 minutes on the first cycle of night cooling. This achieves temps just under 60 F. It then cuts off so the freezer can cool to -6.8 C again. This takes around 12 to 15 minutes. It will then run again for around 10 minutes then off again for 15 or so. The enclosure is cooled the final 10 degrees by the end of two or three such cycles. It then only activates for a few minutes as needed to maintain the low temp for the remainder of the night. The freezer is plugged directly into the wall and set to the coldest setting. Initially I had planned on using the ITC to regulate the freezer for fear of freezing or below freezing air entering the enclosure. This does not appear to be a concern with this configuration however it might be an issue with a more direct input from freezer to enclosure.
That's it for now. Thanks for taking a look. Questions and comments welcome.
Happy growing,
-@.