Gauging the efficiency of our heat pumps using a temperature model for our house that I established last winter when we were still heating mostly electrically. This allows me to work out the effective coefficient of performance.
I think this would be an interesting experiment. If the fan is moving a lot of volume, a smaller cover wouldn't prevent enough snow from getting pulled through the unit. A larger cover would limit the amount of snow, but could limit air flow and not distribute temperature as quickly, making the unit less energy efficient overall.
I don't think you would need any kind of screening. Just a large enough roof over the unit and maybe some slat walls. I think screen might get packed full.
Finally got it up and running. The only delays we had was because we realized we needed some extra parts (I’ll list that below) ru-vid.comUgkxihMYiJNXcHdbH-7ihymsLz61l7jVyb5O . So we have a loft where our current hvac just couldn’t seem to keep cool during the summer. We have been using a window unit since we bought this house over 6 years ago (all the houses in this neighborhood were built in the 80’s and majority of the houses built like ours use a window unit). I hate window units because they are just so noisy and the one we had really only cools one side of the loft. I had contemplated upgrading our current HVAC, but with all the rising prices these days, it would take years before saving up enough to do that. With the advice of my father-in-law (used to run an HVAC business), he recommended we get an inverter instead. We thought we bought everything we needed, but there were just a few other parts we didn’t anticipate needing (which is what caused most of our delay). My friend and father-in-law did all the work to get it installed and running and now we have nice cool air circulating nicely throughout the entire loft. It is very quiet and even the outside unit is much quieter than our main HVAC unit. Saved ourselves thousands getting this.
We have 7 mini splits with two condensers at our house. Installed them 3 years ago. They work fantastic, even when it gets very cold outside. A lot cheaper than our old baseboard heaters, plus we get air conditioning in the summer.
I guess it depends on where one lives: Here in the very hot desert with relatively mild winters, I have a 6 zone Mitsubishi system but it is ducted with one exception of a ceiling cassette in a utility room/home gym. I could not imagine the ugly boxes on the walls.
In Finland covers or canopys for air pumps outside units are rather typical, those would prevent snow issues. Would assume that depending on model they would somehow impact to air flow also, but guessing they would have minor impact. They also hide the ugly white plastic, which seems to be only option by many producers. Considering to make one with homemade bandsaw?
All AC guys I've talked have said to never use those covers as if they hinder even bit the airflow, efficiency apparently drops quite much. Don't know if that's true, but guy who installed mine was at school same time and I believe him. Outdoor units are indeed though quite ugly. Outoa kun meinaa, että imee lunta kitusiin. Ei itsellä ainakaan ole moista ongelmaa ollut koskaan.
I was thinking you could build one like a custom range hood with a style like shaker or tudor or something, even copper or steel if it looks good with everything else. If it's big enough it shouldn't affect the fan much I would assume, but how big before it looks ugly.
@@jothain That is not true that you should avoid using covers! But what one should consider is the area of the intake fins, and that the available area around the unit should be greater than that. The instructions recommends a minimum distance from wall and surrounding obstructions, so your AC guys should pay attention to those instruction. Almost all outdoor units suck air from behind and blows out the front, if you block the top and one side of the unit, the remaining area on the bottom and the other side should be as large as the whole fin section.
@@everythingexplained that's not true either. Check out Mythbusters. I think it was there proven that those areas are actually really small that need to be in use. Reasoning on ac guys seem to be that airflow needs to be very laminar and even small obstruction would break that.
@@jothain As an HVAC guy myself I agree generally any type of cover will hinder airflow decreasing efficiency way more than it will help with defrosts. If you are going to do something of the sort you never want to cover the sides and you want to leave ample room above the unit for air flow. I believe minimum distance above for a awning type cover is somewhere in the 2-3 feet range.
Man you are amazing. I'm off the grid in a tinyhouse, so every Wh counts and I've been dying to know about all these things! Thanks for all the work! On a fun note: it's crazy seeing your numbers of 80-100kWh per day, compared to my 5kWh per day D: :D
What do you do to consume 5 kWh per day in a tiny house? You need some more efficient appliances man. I run a regular house with 2 freezers, 1 fridge, washer (no dryer), stove, water pump, water heater, computers, lights, 60 inch tv, ... on not much more, about 6,5 kWh per day. All A class european efficiency score appliances. Freezers consume 90 kWh per year.
I installed a DIY 18K unit over the summer (primarily for AC). I've been quite impressed at the offset it's produced to the oil boiler, especially in the shoulder season. Rough math so far has me saving half my annual fuel oil usage, with a modest increase in electrical usage. Fuel oil is around 5$/gal, and I usually use 6-700gal/winter. It's paying for itself quickly at this rate. Would love to have the granularity of the data you collected though!
Yeah, your numbers are spot on. In my case, heating cost is about a 1/3rd compared to using my oil fired boiler but that's because my boiler setup is super inefficient. Just going to a cold fired boiler would be a huge cost savings in my case.
@@chrisE815 A lot of people who read this have not yet installed anything. My advice to people who think of making a move is to look at the insulation of their building first. Insulation you buy once and you benefit for every year after that. Insulating can cut down your energy use so much that it doesn't make sense anymore to make an expensive switch to something else.
Interesting. I've always wondered what is the efficiency of those things,... I've seen overall numbers anywhere from 2 to 5 times more efficient. Thanks for all you testing Matthias, this is very informative.
Nice job with the data collection and explanation of findings. I installed 3 mini splits in my house in FL and turned off the old central air. Our electric bill went down from $400 month to $150. To say I am happy would be an understatement. I know a lot of HVAC guys don't like mini splits because they are hard to work on. Right now that is not my problem. If worst came to worst I would just install a new one because the electric is already there and the hole thru the wall.
Great discussion. We installed a hybrid water heater with similar function to the minisplit from a gas water heater. You’ve inspired me to start collecting a bit more data with external sensors. Of course, to proof is usually in the utility bill.
If you have extra temperature sensors I’d recommend adding one each to a liquid and vapor tube on the coil. It should help you monitor how efficient the OD coil is performing. As long as that temperature is close to outdoor ambient then your od coil is performing well.
Since this is an inverter unit, measuring the temps on the refrigerant is not that informative. The unit will have pressure and temp sensors giving feedback to the inverter that control the compressor and changes the flow in the system. The one thing I could think of is for detecting unneccesary icing of the evaporator, ie. liquid temp and gas temp are close and way below outdoor temp, but that should the unit detect. To see if the unit is performing well you should measure the power that the unit consume compared to outdoor temp and indoor temp.
These things are super common in Sweden and has been for 20+ years. I use one to keep +8C in my workshop. Works great! Also common is geothermal. My borehole for the house is 250m deep.
@@dimmacommunication It's a borehole, we have those (it costs money to bore ofc). Now here on private Land we are only allowed 100m i think. But we do have warmer temperatures overall, so it's fine.
I love this video, I just put a minisplit in my workshop and have been thinking about doing similar tests, but it seemed like too much work. Thanks for doing the work for me :) !
Thank you and good job on including the defrost cycles into your COP. Plenty of people wouldn't include the "bad" parts and instead would just tell themselves how smart they are using a mini split. COP tends to dive below 2 when it gets cold, and between that and the high cost of electricity here ($0.34 per kWh) a mini split is no better than the cost of heating oil.
Great video! Yes, I also would add a roof to the outside unit. Join the house wall to the top of the unit to stop the snow from being sucked in. Maybe a few inches on the side. The remaining 75% air flow on each side should be enough.
I've been watching all of your videos for a while now and only today found out that you are in NB. Hello from Fredericton. Moved here a few months ago and absolutely love it so far!
Your attention to detail and knowing how to measure are impressive. Have you considered placing a roof over the mini split outside unit to keep the snow off?
@@paulettelambert7965 But it would mean less defrosting cycles. That was the whole point in recommending a shelter for it. Plus it would be less likely to rust so soon. Have you seen how those things have rusted before? You see them frequently all rusted up. Hopefully newer models have learned.
When you live in a coastal climate it is very important to cover the AC unit, otherwise the casing will be damaged in a few years. Covering it will save you many years of use and money! I live in a coastal region and had a AC go bad in 5 years.
Yeah they are great, I have mini split of that particular manufacturer Midea, I think they are more efficient because they are using inverter motors for the compressor. I'm very pleased with the mini split unit so far, they are up to the job.
My 8,000 / BTU seer 21 Pioneer split heats my 23 foot travel trailer at 8 degrees no problem. It draws a constant 400 watts to do so. Above freezing, in the 30’s it draws around 240 watts and cycles on and off. My trailer is super insulated with R15 in the walls, R23 in the ceiling. There is nothing like the luxury of good insulation and one of the more efficient mini-splits. Of course a high Seer rating and the time of purchase it a bit difficult due to the initial cost being nearly twice as much. Because my power requirements are so low in both Summer and Winter, I can run all this with solar. Note that when initially started and the Pioneer is running at maximum effort, it can draw as much as 980 watts for a short time. Thanks for the video.
I installed a mini spit in our house in December of 2021, I've not seen mine ice up,even after our paltry midwest snow yesterday. I really appreciate seeing the visual evidence that I suspected about its energy efficiency, I feel like between the air conditioning and heating,I've saved a ton over my natural gas,and old air conditioner.
Mini splits are amazing, we're using one since this winter. Some are better at heating than others though, COP 4 or 5 is doable for really optimized ones. Around zero C we're using the same amount of electricity of 3 dishwasher cycles per 24 hours.
We installed a minisplit heatpump last year and used it that winter. This year in New Hampshire electricity is extremely expensive so we are only using our cordwood stove. We have an LG red system with two compressors and six indoor units. I didn't notice much in the way of defrost cycles last winter but I was not monitoring it as closely as you are.
I have a Mr Cool which i believe is a similar unit and another cree. They both do a great job. Your observations match mine exactly. Doesn't do the best in cool humid air, builds up with ice. Once the air drys it does alot better. I keep a wifi temp sensor near the output and have been monitoring as well. Outside humidity can make a huge difference in how quickly the coil reaches max temperature.
Thanks for the thorough and detailed research. I was considering a similar split unit here in the UK - more for the air con. But the real world data about the heating aspect of it is appreciated. I was skeptical they could perform as good as they state.
Build a little lean to coming off the house to cover the outside unit. It'll help with snow ingest in winter and with direct sunlight in summer. Increased efficiency year-round.
We installed one of these as part of an IT server room hvac and the contractor specifically mentioned us requiring a sub-zero add-on to prevent the unit icing up (winter operation in southern Ontario). Perhaps you might want to speak to your hvac person to get information on that.
I think my minisplit system has resistance coils in the outdoor unit to defrost itself. I didn't realize that some units didn't have this. Love your data gathering and analysis!
This is the key with reverse cycle systems, it is one valve and little electrical change between heating and cooling but does it in one vs independent units.
Your experiements/work with cyclone seperators should come in handy for building a duct for the outside units that settles any snow out before feeding dryer air to the unit.
If you want to prevent frost on the back of your unit, try putting some propylene glycol into a spray bottle and spraying a thin layer onto the freezing surface.
+1 on some sort of cover over the outside unit. My unit is not up against a plain wall... My workshop is on piers with air flow under it (floor joists have insulation between them) So air into the unit is coming from a sheltered area. The little corrugated plastic roof extending out over the unit from the shop wall therefore does not restrict air flow. That roof helps also to keep debris from being sucked into the coils.
Matt, This was very interesting. I understand they are more efficient than resistive heating but its hard wrapping my mind around it when they are driving a compressor. Just a suggestion for the summer months eh! I've seen the evaporator units make a mess of the walls when the condensation drain clogs up. Be sure to keep the drains clear! Best Wishes, Tom K.
Here some of our outdoor units actually have a resistive heater coil around the outside refrigeration coils to periodically defrost ice blocks without having to reverse the system :) They call sell those models here in the more southern areas (they cost more and the feature isn't needed in more northern areas).
I've used air conditioning all my life for both heating and cooling. I'm from the UK Daikin 1800 BTU split x2 stick it on brackets put it on the wall outside works a lot better. A decent AC will run the inside fan very slowly in defrost. I'm happy with both my units even at - 10 Degrees C.
some great information here thank you for putting this video together! I did want to give you a heads-up that when the units go into defrost, they aren't heated up with an electric element, it's the refrigerant inside the coils that are pumped in reverse. that is why you felt cold air when you turned it to air conditioning mode to dethaw it.
Very informative, thanks It would be interesting to see some data from a tankless water heater in comparison with the storage tank variety. Food for thought sir 🤔
Great vid. Just wondering how you are using 40kwh per day before you need heating? Is your hot water electric? We use around 6-7kwhr but have gas hot water and cooking. I also live in a much milder climate.
I use probably 2kWh per day just heating shower water, and 20kWh for my 100 mile commute. He also mentioned dryer, if he has typical electric that is 3-5kW for however long he is using it.
Very informative. As you alluded to, in pursuit of efficiency and economic pay-back, one must always consider the complexity of the systems and therefore their reliability. One significant repair could consume all of the fuel savings and more.
One of our unit have an auto de icing so it stops heating for a couple of minutes when it detects icing. It is computer controlled and even have prepare mode before heating in the morning. Our other unit is just cheaper one and heats non stop until it ice up. We don't usually use the dumb one because it is the bedroom. The smart one is in the living room even have an app so you can track your 2 years of power usage. Current year is overlaid over last year.
i received a presentation on samsung VRF systems at work recently, where they showed that they have air pressure differential sensing to determine if the unit is iced up, so that they can potentially run the defrost cycle less frequently. not sure if others do this too, but thought that was cool
Nice video. Someone told me if you keep your mini splits outside in an enclosed environment like a box, it saves a lot of energy since it will not be exposed to elements. This could make the number of times it needs to defrost less saving energy. I don't have one myself so it is just something that i heard and thought i will let you know.
Cover from elements and shade from sun is good, but restricting the airflow is bad. Roof with no walls would be ideal but most people want to hide them vs draw more attention to them.
Im running mini split in the garage/workshop. Runs year round to keep temp up and reduce moisture in the space. Prior install ran dehumidifier that was a power hog in comparison.
It would nice to see the data show actual ambient temp, there is lots of video's show how this works in what appears to be moderate temperatures. I live in a area where it can be -20 to -30Cfor a good portion of the winter. Electricity costs are about $0.31 per Kw/hr, natural gas is about $5-7 / MMBTU. So based on what he is indicating there is no cost advantage.
10:48 - would absolute humidity (g/m3 H2O) be more relevant ? It is after all the amount of water that freezes to the coils. +5 C / 80 %RH = 5.5 g/m3 H2O vs. -5 C / 80 %RH = 2.7 g/m3 H2O.
Thank you for such a detail analysis. I'm doing all the painstaking measurements so that we don't have to do. Could you please link the model of the mini split?
What an interesting video, I'm so glad I watched it. I'd be interested in knowing how much energy is used in the defrosting process over the course of a season, and whether or not it would be worthwhile to have a couple of air filter/screens that could be manually hot-swapped when they got clogged.
In your video you mention the outside humidity several times, but I was wondering about the indoor humidity. With my Gas heater on in the winter it gets quite dry inside and I was wondering if you had the same issue with your minisplit. Do you find the need to run a humidifier in the winter or is this not an issue? Also, in the summertime my central AC does a great job to bring the Georgia humidity down since my thermostat automatically turns the AC on if the Humidity level is too high (even if Cooling is not needed). So how well does your minisplit reduce Humidity during the summer (or is data not available yet)?
They type of heating has no impact on the humidity. (well, maybe wood stoves might have. Since they exhaust quite a lot of air that has to be replaced by outside air)
Great presentation brother, I live here in New Brunswick also, just installed 4 , seeing how I can get the best efficiency, you were very thorough, going to check out more of your vids TY
Seems like a shed around the compressor would reduce the defrost cycle and increase efficiency in the winter. Although I don't know how that would effect cooling efficiency in the summer.
So, the COP that you plotted seems to be in line with what Alec of Technology Connections/Connextras said about his system. Yours had a few more details and statistics, but that works for me.
Your unit will have a thermistor on that outdoor coil. The board will look for a reading for defrost to activate. It’s normally a temperature after a time period.
If you could build a small roofed area over your outside unit, it would not only keep the snow off, but the cooling effect from the shade might help during the summer, albeit, marginally.
Great analysis, and since you recognise the likely effect of humidity on the system, would a next step be to add humidity sensors around the outdoor unit to verify if the frosting is directly related to the fins dropping the airflow below dew and freezing points? I've been heating a small property in Scotland for 9 nine years using a Daikin ASHP and love it. No other heating and my entire annual electricity usage is 2000kWh. Mine does also freeze up, anecdotally mostly in the same mildly frosty ambient conditions as yours, but mine seems to leave the water pumping round my radiators while it defrosts, causing them to cool but not get particularly cold relative to indoor temperature.
We have had a mild winter this year (im in Freddy too). Im down 800kwh from same time 2022 and 1200kwh from 2021. This week will be a good test of the minisplit! Brr.
I hope you managed to get a reasonable install price for the mini-splits (or did it yourself). When I called an HVAC place here to get a quote for a mini-split install, they wanted a rather ludicrous markup, two to four times high a price as it should have been. No way I'm getting ripped off like that, I'll either install it myself or just wait until someone's willing to offer a fair price.
After 7.42 I realised you have reached level 100 Electrical Engineer. I was trying to guess if you were mech or elec, but the instrument comment is 100% elec haha! im mechanical, and loved the content. PS most elec's always take it to the next nerd level and that brings me great joy! I found this video by looking into misting the condenser (in cooling mode obviously) to increase the efficiency, my search is inconclusive and you have all the gadgets to run a test in summer.
@@matthiasrandomstuff2221 After everything I've looked into, I agree. My water is quite hard and the calcium build up will just kill the efficiency long before corrosion kicks in. However, I ended up setting up a manual misting system to assist on hot days >40 deg C and it made a noticeable difference. I would be super interested to see what results you could get even if you just mist with a garden hose for 30 minutes.
Here in the north of Scotland we find that there ios more variation due to the high relative humidity and the significant number if days that are cold, around freezing but wet. As such the defrost cycle has to run far more often.
I installed minisplit for my shop myself. You need vacuum pump to do so. Install is very easy, If you don't want to buy vacuum pump, after install you can hire HVAC guy to start it up. There is few videos on RU-vid showing that job. I believe my unit is senville. I can also operate it from cellphone. I got one called arctic weather. Runs on 240V and works till -30Cor -22F. so far so good and is super quiet in and out. I wish my central AC for the house would be like that. I got it mainly for summer/AC. I have forced air NG furnace. But few times I tried it in -25C
my apartment has a similar unit, we don't use it in the winter due to the building's baseboard radiative boiler heaters, and the lack of consistent airflow. But dang is it efficient.
It is always worrisome when the coils freeze because the expansion of ice as it builds up could easily fracture some of the thin coolant lines. I also have reservations about keeping circuit boards in a very wet environment.
coils ice build up is typically thru sublimination. As such, there is no liquid to solid transition happening on the coils, so I don't think the water expanding when freezing is an issue. Except for perhaps the remaining drops of water after a defrost cycle.
Matthias Very helpful & detailed analysis. Some additional helpful information would be what the heating specs are for your Mini split regarding efficiency and outdoor temperature. Also a few of the new minisplits are rated for 100% efficiency down to -15 degrees below freezing. What is the difference and how do the new models achieve the improved heating efficiency? Would it be possible to add on an aftermarket part to upgrade the heating capacity of existing minisplits? I'd love to see a step by step process for setting up the sensors to create this video. Thanks again!
@@matthiasrandomstuff2221 This is the video I have been waiting for! I install these for a living and have thought about the issue of humility and defrost. Thankfully where I live it’s usually above 40f and they don’t have to defrost at all. But once defrost has to take place comfort and efficiency goes way down. All the manufacturers give is the HSPF, so this video is very insightful. What is the HSPF of the mini splits at your house? If you don’t know the model # will work and I can look it up that way.
You refer to "wind effect" as partial explanation for temp difference between intake and output air of external mini-split unit. Someone can correct me if I'm wrong, but I believe "wind chill" applies only to the effect of moving air on exposed flesh. The temp sensors that you placed in that unit, I believe, would not be affected.
Do you factor longevity into your cost savings? I'm a hvac apprentice and see many minisplits fail due to poor air filtration, refrigerant leaks, and main electrical boards burning up occasionally. Some of this can be attributed to poor installation, but some seems to be from just a poor design. So if you have to replace it before it pays for itself, is it worth it?
The good quality ones last years. I have a Samsung at work that cools a server room, runs 24/7 365 and been at it for 8 years with nothing needed but occasional cleaning. Cleaning the funk off the fan wheel on the indoor unit is important along with that coil, but there are cleaning kits that make it easy to do it. Oldest one at my house is going on 7 years now, with no issues either.
If you turn on the Turbo mode, that will force the basepan heater on and warm up the house more quickly or hold a higher temp over night, of course at the cost of more power usage. Mine never ices in AZ.
If you get enough ice build up that you need to assist the unit in defrosting, you should ensure all ice is gone otherwise it will start building again in the same areas. In a worst case scenario the ice can shift the coil and damage it. Warm water can be used to melt the last bits of ice.
ever try to make a large insulated box with vent holes to keep snow off and hopefully being a box make a small micro climate that maybe keep it from icing up so much ? im just currious we dont have mini splits but intrested in getting one
Here in Australia, we pretty much use them for cooling. trying to sleep at night when it is 26 degreesC and 80% humidity is impossible. Can't live without them in Summer in my part of the world
What is the rated efficiency of your minisplit? Did the measured performance come close? My impression was that many systems' spec sheets these day advertise COP around 3 or 4, so your results were lower than I was expecting.
@@rkan2 I wish he had said. I bought 2 smaller units, one with very good HPSF and one with very good SEER. I put the HSPF unit on the south side and use that for heating on all but the coldest of days (SEER unit is set to freeze protect and will kick in if absolutely necessary) and put the SEER unit on the north side and use that for all cooling.
I am experiencing the exact same thing with my 10 year old mitsubishi. Around 0 it needs to defrost much more often, every 1-2 hours. Also it has a heating element in the bottom of the outside unit to prevent water to freeze in the bottom of the unit when defrosting.
If you were to build a structure around the outside unit, a greenhouse might be a way to achieve greater gains. If you add barrels of sand for thermal mass, it would become a hybrid geothermal system (above the ground.) In summer months you would open the Windows and doors (switch to screens) and hang opaque shade cloth inside the roof and walls to intercept sunlight from reaching unit.
We put in a four inverter Mitsubishi mini split in N Ca. Starts getting less efficient under 40f and around 32f just not that good but we have propane supplemental. It's saved us 1000s this last year on propane and electricity in both Summer and Winter. The best range is 40- 110 f.
