Mini split confusion (efficiency and sizing)
I'm right on the edge of buying a mini split for our shop space and I'm having a bout of indecisiveness.
To preface, we are located in south/central Texas. The shop is a standalone structure, is fairly well insulated but has a 2-car garage door and a single-pane window, so it isn't ideal. It's 625sqft with 9 foot ceilings. We have various tools that will be in use but nothing that creates excessive heat.
We are quite limited in funds so I'm not going with an HVAC company, nor am I going with a mr cool or other diy friendly unit due to cost. I'm capable to do the install myself, I'm not overly concerned about that.
I was originally looking at the 18k (1.5ton) senville leto. I ran various calculators and they all suggested this size would be enough up to 1000sqft or so. However, since I have 9 ft ceilings and I live in a hot climate and I have the big door and crappy window, the calculations pushed my 625sqft up to around 900 or so equivalent sqft in some cases and in others as high as 1200.
Due to my circumstances, I think I've convinced myself to move up to the 24k unit instead. I don't think it's too over provisioned for my specific scenario but I would like to hear your thoughts on how off the mark I am here.
Apart from size, there's also the question of efficiency. The other model I was looking at is the Aura by senville, and the difference is a higher seer2 rating and energy star certification.
Now, doing rough math, the difference in efficiency would be paid off by the savings of the more efficient unit in something like 8 or 9 years based on projected usage and my energy costs. I'm a pessimistic person and don't expect this unit to last 8-10 years. This is a cheap way to get the space comfortable to work in so that my side business can progress, and I would think if it's still going in that amount of time, I'll be able to afford a nicer unit by then.
However, after saying all that, I do notice that the capabilities of the Aura unit are greater. It is advertised to work in -20f weather while the leto works in as low as 5f.
Now, being in Texas, my primary concern is cooling, not heating, but no where can I find if the Aura system is more capable in hotter weather like it is in colder weather. This is slightly concerning because it seems most people use these primarily as heat sources and secondarily as cooling sources, and my situation is reversed.
Does anyone have any input as to whether the higher efficiency system will make a noticable difference in cooling performance when it's 110f outside?
Thanks for weathering my wall of text.
I live in Australia, and split systems are the norm here. I would recommend looking around at Australian sites when you do your research. Whirlpool is a really helpful forum for discussions like this. Just be aware that Australia is a large continent, and some regions here are quite unlike Texas (e.g., Queensland is tropical rainforest, so they have different considerations than, say, South Australia); when climate is relevant, people will mention the region that they are in, but they will not necessarily mention their particular climate challenges (they assume that the readers are already familiar with the different climates around the country).
My personal experience is that the split systems used around here (southern Victoria, which is a Mediterranean-type climate with hot summers and mild winters — about equivalent to USDA zone 9-10) are more effective at cooling than at heating because cool air sinks down to human level. I also have not known them to fail during hot weather. However, they can struggle to keep up with the heat if they are not powerful enough. I live in a poorly insulated attic above a workshop (which was originally designed to be a wood drying room, not a place for people to live), which is far from ideal for heating and cooling. When we are predicting a very hot day here, we keep the curtains closed all day and we set the A/C to start running at full blast starting early in the morning before it's really needed (we just put on coats), and that keeps it manageable when afternoon hits.
The only time that strategy really failed for us was one hot day last summer when we had a power outage in the early afternoon that lasted until the evening. Our indoor temperature reached 91°F (33°C) — which was certainly much cooler than it was outside, but still super unpleasant. In a more insulated space or less attic-positioned, the power outage wouldn't have been such a disaster.
So the other thing I would urge some caution about: does your workshop generate a lot of dust? If so, it will be extra important to stay on top of cleaning the filters. Even so, some especially fine particulate matter will end up inside the split system, which can cause some issues. We (being above a woodworking workshop) had this issue develop over the course of 3-4 years and had to get the unit completely cleaned out, which was not cheap or easy. It didn't cause any lasting damage, but it caused the unit to work less effectively for two reasons: the fan blew at a drastically reduced capacity, and the thermostat was taking incorrect readings and shutting itself off too quickly (which particularly affected the unit's heating ability). It also caused a minor indoor water leak.
Thanks - I'll definitely look into that, that's a good idea to research like this. I can understand if we hit record highs that it may be uncomfortable but if that's a 1% of the time type of thing, I just won't work in the shop those days or work in the mornings. Still, I would definitely like to have a unit that can keep up.
Yes, we do have dust collection but as you are probably well aware that doesn't catch it all. I'm planning on making a plenum like Jay Bates did for his mini splits, which should leave me well enough off but I'll definitely have it on a schedule to check/clean.
I think if you build that, you will be in very good shape! Those filters are much better at collecting fine dust than the filters that split systems usually come with (which are more like a very fine bug mesh).
Hello fellow (for the time being) Texan!
The answer to the hot weather performance is in the AHRI certificates:
18k BTU Aura: https://senville.com/content/certificates/SENA-18HF-AHRI.pdf
18k BTU Leto: https://senville.com/content/certificates/SENL-18CD-AHRI.pdf
AHRI tests BTU capacity and efficiency at 95F, both are performing at their rated 18k BTU at 95F, the Leto has a 2 point EER rating disadvantage at 10.5 vs the Aura's 12.5 at that temp.
Aura is more energy efficient when working the hardest, but not better at actually removing heat at that temp.
How often do you open the garage door (I assume you've insulated the door itself already)? I ask because one of the greatest, and cheapest, insulators out there is an air-gap. A roll up garage door curtain with magnetic strips along the edge on the inside of the door (assuming your door is inset to the wall and not mounted inside the building) will put an air-gapped barrier between the leaky door and the climate controlled interior.
Nice pun at the end.
You're escaping?? Take me with you! :P I got people in West who can send us kolaches in the mail, no worries there
Thanks for the links - I don't know how I missed those but that confirms my decision to stay with the cheaper unit as I don't think the cost savings will materialize before the inevitable demise of the compressor or some logic board.
I would say we open it sometimes.... not a lot but when we are bringing material in or if I have to sweep/blow dust out of the shop it's easier if I just open the big door and pull out the leaf blower. I think that'll happen less when I get this unit and some other things handled (like actually setting up my dust collector). I have never heard of these curtains before but I see a couple on amazon... very intriguing. I'm kind of wondering now if I can find one that seals all the way around the door, the ones I've seen have weights at the bottom but don't seal and part of my issue right now is bug intrusion (spiders mostly, which I'm honestly fine with because they eat flying bugs and I don't like flying bugs, but they're getting too numerous and obnoxious now, putting webs where they don't belong) so having a full seal around that door would be awesome for that too.
I'm still on the fence whether I should be going for the 24k unit or the 18k.... I think I'm still convinced to go 24k but I'm ultimately undecided because on one hand, if it's undersized it will cycle properly but it won't fill the task I need it to, which is to make the shop space comfortable to be in so that I will actually go out and work in there, but on the other if I overprovision it will short cycle and the compressor will be getting it's angel wings a lot faster than it otherwise would. If they made a 21k I'd have probably already bought one (and I know other manus have them, maybe I should keep looking but the senvilles are on sale and I have a 100 dollar off coupon too)
👉😎👉
Dude, I am this close ➡️⬅️ to getting a Czech babička to teach me how to make kolaches and just straight up open a legit kolache place in Colorado; with the sheer number of Tex-pats up there I bet it'd make a killing.
Leaf blower is my clean out method as well and same with the spiders. I'm down with sharing space with y'all spider-bros, but when you're running a web from the wall to my cars and getting in my face we got a problem!
Look up "dock door curtains" instead of garage/home stuff. See here - https://www.curtain-and-divider.com/product/roll-up-dock-door-curtains/ - it uses a roll up method with velcro fastening at the edges to create the full seal. Since you're DIY/handy a heavy duty tarp or vinyl sign material, plus velcro or magnets at the edges would resolve the full seal requirement and be much cheaper. You can do the same thing, with clear vinyl, for the single pane window you have.
They've got a 5 year warranty, but that might require proof of "professional installation", so if you go larger and it dies pre-maturely because of the short cycling you may have it covered by them anyway.
Haha West is my hometown so I've got some family recipes but I can't ever get them to come out quite like grandmas. You need about 2 truckloads of butter and sugar to get close :) funny that Colorado is one of our "if we ever get outta here" spots, even had our honeymoon there.
Thanks for the info! I'll definitely look into these.
If that's what it takes, that's what it takes! Our friend group has a group chat that always includes a "What's your order?" if one of us is traveling through West, knowing that being disowned from the group is the punishment for not returning with kolaches in hand.
Pretty much the same here. I passed through Colorado a few times working and then more recently when picking up project cars, took my wife (then girlfriend) there to propose, then back for honeymoon and began plans to move, but got put on hold for various reasons and now we're at the point where we can do so (despite the inflated costs) and during all our talk about wanting to move up there her family went ahead and did so. So we have extra incentive to be close to her mother, brother, sister-in-law, and newly minted nephews.
Good luck on cooling the shop!
Take a look at https://www.loadcalc.net/. The form it uses, Manual J, is what professional HVAC installers use to calculate the load. At least when they're not fraudulently making random guesses and faking the form afterwards!
It's not super intuitive, but it is very accurate!
I may have to get my buddy chatgpt involved to get it filled out right but I'll definitely do this, thanks!
What is the price differential between the two units? Are you doing anything else on this project or just HVAC?
I would seriously consider getting the bigger unit. While you aren’t doing heat-generating work now, it gives you flexibility in the future, and even “normal” shop work can get hot.
Only like 200 bucks ... I think I'm going to go for the bigger unit, hopefully I don't kill the compressor within the first couple years