So, my Hubitat automated 6X8 Greenhouse that I added last year is just getting too hot in the summer to be used, even with shade cloth and the vent fan I added.
After May of last year, the greenhouse was basically unusable on a sunny day, the vent fans cannot even get it down to outside air temp.
So I ordered this, I'm still waiting for it to arrive. Has anyone used such things, and how well do they work?
I'm also adding another vent fan to draw air in on the door side, in addition to the larger one I have now that blows air out on the other side. I should get a good air turnover with both fans running, so I'm thinking this swamp cooler might actually do something.
It will be added in to the automations already in the greenhouse. The vent fan comes on now by temp using a thermostat device, I will just add the swamp cooler to come on as well when temps go above setpoint.
Am I going to be horribly disappointed with how much the swamp cooler can cool my small greenhouse, or did I find the solution to my heat problems?
Yeah, we get some humid days in VT summers, so I realize that will limit how effective it can be on humid days. I've read there needs to be full room air change-over about every three minutes. I think my vent fans can achieve close to that to vent the humidity it creates.
Assuming it works, I will also be adding an auto-filler to the tank, similar to the auto fountain filler I made last summer with an irrigation valve and and a leak sensor for my outside fountain.
I've never personally owned one. I grew up in and still live in the mid-atlantic and never encountered. A few years ago I took a trip to Utah and the place I stayed in had a swamp cooler. It made it bearable but it's certainly not A/C. The key point is that these are "evaporative coolers" and the humidity needs to be low enough for them to function which rules out practical use in vast swathes of the US.
Evaporative cooling exploits the fact that water will absorb a relatively large amount of heat in order to evaporate (that is, it has a large enthalpy of vaporization). The temperature of dry air can be dropped significantly through the phase transition of liquid water to water vapor (evaporation). This can cool air using much less energy than refrigeration. In extremely dry climates, evaporative cooling of air has the added benefit of conditioning the air with more moisture for the comfort of building occupants.
The cooling potential for evaporative cooling is dependent on the wet-bulb depression, the difference between dry-bulb temperature and wet-bulb temperature (see relative humidity). In arid climates, evaporative cooling can reduce energy consumption and total equipment for conditioning as an alternative to compressor-based cooling. In climates not considered arid, indirect evaporative cooling can still take advantage of the evaporative cooling process without increasing humidity. Passive evaporative cooling strategies can offer the same benefits as mechanical evaporative cooling systems without the complexity of equipment and ductwork.
To put more simply, here's some AI (probably wrong) BS:
Evaporative coolers become ineffective when humidity levels exceed 50%. They are most effective in conditions where humidity is below 30%.
Well, I will add that this cooler is way over rated for a 6x8 foot space, this unit would normally be for a large room. I'm not sure how the chart would account for that. Size appears to make at least some difference.
"A 2154 CFM (Cubic Feet per Minute) swamp cooler is generally suitable for cooling spaces between 500 and 1,000 square feet ." The greenhouse is 48 square feet.
" * Faster Cooling: A higher CFM allows for a faster, more effective cooling of a room compared to a smaller unit.
Overcoming Heat Load: In areas with poor insulation, a slightly larger unit handles heat gain better, as noted on Rosanna Heating and Cooling.
Limitations: If the humidity is very high (above 70%), any swamp cooler becomes less effective because the air cannot hold more moisture, rendering the size difference less significant."
By the chart, assuming around 70% humidity for a VT summer, it drops off for temps at 95 degrees, but at 90 is shows an 8 degree drop. I expect to get better than that from this over-sized cooler, given I will also be turning over the air constantly with vent fans.
Time will tell, I will report back on the effectiveness once it is up and running on a warm, sunny, humid day. I'm not doing any automations for it until it proves itself.
I've been in two places that used a swamp cooler. One was a single-wide mobile home in San Angelo, TX. The other was at Fort Huachuca, AZ. When the humidity is low, they work great. When the humidity increases, they become less effective. They can add enough moisture to a house to make mold a possibility, so watch out for that.
The other thing is that the pad gets all the contaminants in the air such as dust, bacteria, and mold spores. If the water is very hard, the pad will also get coated with that hardness. The stuff that gets into the pad can also continue through to the house. The ones I had did not have any air filtration on the output of the cooler. I believe that exacerbated my wife's asthma.
Are you planning on putting this fully inside your greenhouse or on the outside blowing in? You will need a way to exhaust the air if it is outside. If it is fully inside, then it is not pressurizing the greenhouse, but it will be increasing the humidity greatly. I would think that just a fan or two blowing air into the greenhouse to increase air circulation coupled with your vents to exhaust the pressure would likely be more suitable for a greenhouse than this swamp cooler.
I have a circulator fan inside the greenhouse, as well as the 12" vent fan blowing out. I have a 6" new vent fan that will blow in, need to install still, though.
It is going inside the greenhouse, it needs to recirculate, there is really no outside venting involved with these.
It was actually an issue last year that the heat in the greenhouse burned off humidity, and the humidity was always lower than outside, too low for the plants, really. Adding humidity to the greenhouse will be bonus, if anything.
The thing just arrived ten minutes ago (way ahead of shipping schedule). It is 33.8 F outside right now, and the greenhouse is going over 70 already. Vent fans are taking care of it without issue right now since it is so cold out still, but I am going to try the cooler out today and see what the humidity levels go to. Tomorrow is going over 60 and sunny, so tomorrow will be an even better test.
Edit: I has been running for 15 minutes on low. Temperature dipped to 66, and is now holding pretty steady at 68. Vent fan is not coming on every ten minutes like it was before I added the cooler. Humidity has increased to 66%, but this is not a true test as the vent fan is not running to get rid of humidity like it would be on a hotter day.
Edit2: It has now been about a half hour, I put it on Medium ten minutes ago. Temps are now dropping, humidity is staying at 66% even without venting.
That is something I had not considered, but it will probably be an issue over time. Fortunately, it is not in the house where people are breathing. Looks like I could remove the pads for cleaning or replacement if needed at some point. Thanks, that is something I will monitor.
This is some China device, and the instructions are horrible, and I think written by AI. The instructions actually say "It seems the way to fill it is by lifting the panel at the base of the unit". The panel is actually on top of the unit. The section on maintenance just says it is prohibited to open the unit or modify it in any way. While it mentions that the the pads will get dirty and clog, they suggest no actual maintenance for when that happens.
I'm going to try and take it apart anyway to convert it to a Zigbee device using a Zigbee relay board, so I guess I will also be able to get to the pads once I figure out how it comes apart (there are no obvious screws, I hope it is not glued together).
Edit: I found screws under the control panel to get it apart to get to the pads. It also looks easy to make this a Zigbee device with a 4-channel board, there are three speed wires and a wire for the cooling pump.
