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In a house I own in Melbourne, Australia, I just replaced an old gas central heating system with 3 new top of the line Daikin mini split heat pumps. The new uni
by fifteenforty 4y ago
In a house I own in Melbourne, Australia, I just replaced an old gas central heating system with 3 new top of the line Daikin mini split heat pumps. The new units can heat the entire house for the same amount of electrical energy that was used to run the FAN in the old gas unit. They are crazy efficient.
Ducts are dead.
The Daikin Alira X is the gold-plated option and cost $8k AUD for 2x2.5kw and 1x7.1kw units including installation. Payback time is about 3 years. The system is oversized, but enables excellent zoning and of course provides cooling which is a must on 40C/104F days.
Why do they seem to be so much more expensive in the US?
- teruakohatu 4y ago> Ducts are dead. Ducted heatpumps are a thing here in NZ and make sense to me, not that I have used one. The heatpump sits in the roof and air is pushed into three or so rooms through ducts. If building a new house I think ducts would be the way to go.
- fifteenforty 4y agoYou have to think carefully about where you run the ducts. They can be a huge source of energy loss. 40% is the number quoted by the EPA. Most roofs in Australia still aren’t sealed. The air barrier and insulation barrier is the ceiling. The roof space itself is not insulated, so the ducts are exposed to extreme temperatures, thus destroying the efficiency. Here is just one article on it: https://newenergythinking.com/2018/10/20/dont-use-ducts/ https://newenergythinking.com/2018/10/20/dont-use-ducts/
- teruakohatu 4y agoI hadn't considered that. My argument with split systems, at least how they are installed in NZ, is that they are usually installed in the main living area and if there is a second unit, in a corridor. So corridors are heated or cooled far hotter or colder than they need to be in order to heat/cool bedrooms.
- deleted 4y ago[deleted]
- thehappypm 4y agoI have two units that are heated by heat pumps in Massachusetts. One has mini splits. You definitely don’t generally put mini splits in every single room (like bathrooms or interior hallways) because each mini split requires tubing, is large, and expensive. No, I think it’s way more likely that you would have them in the bedrooms rather than the hallway
- teruakohatu 4y agoIn New Zealand I have seen small heatpumps in bedrooms, but I would have to say it is extremely rare. But we have many very toasty hallways leading to cold single glazed bedrooms!
- thehappypm 4y agoThat might be a climate difference — it gets below 0 Fahrenheit here every winter, as I understand it, NZ is quite a bit warmer, so maybe the strategy of “heat the core of the house and let it radiate out” works.
- teruakohatu 4y agoThere are historical and cultural reasons for our poorly insulated and heated homes, but "heating the core" is not one of them. In the last few years the central govt has brought in legislation requiring landlords to heat and insulate homes to a certain standard.
- fifteenforty 4y agoExactly. In this example, which is pretty common here, I installed 1 in the living area and then 1 in each of the bedrooms.
- Gordonjcp 4y agoWhy wouldn't you just lay insulation on the ducts, same as you do with water pipes?
- fifteenforty 4y agoUS and Australian units are different for insulation, but in my terms the insulation around the best ducts is R1.5, but good ceiling insulation is R6. 4x difference Edit: not to mention the huge difference in surface area. Ducts can expose your conditioned air to a huge, poorly insulated surface. Bad for efficiency.
- briHass 4y agoInteresting. The code for duct insulation in unconditioned spaces in the US is R8, and they're pushing for higher currently. They also recently undid a long held myth about ducts buried in insulation leading to condensation issues. Most areas now allow ducts to be buried as long as you have R19 above and below, or R30 above. When I just installed a ducted mini for 3 upstairs bedrooms, I surrounded my R8 flex duct with R30 insulation.
- EricE 4y agolol - it's not a myth. It's physics: https://www.youtube.com/watch?v=Vufih-WN5R4 https://www.youtube.com/watch?v=Vufih-WN5R4
- mrexroad 4y agoFwiw, context of this video is metal duct work. You’re not going to see R-8 flex duct buried in R-30 begin to sweat when the AC is running. In terms of controlling the dew point, the duct is no different than the conditioned space at that point. Like you said, it’s physics.
- EricE 4y agoOver insulation introduces new problems like condensation (which causes mold and other nastiness) https://www.youtube.com/watch?v=Vufih-WN5R4 https://www.youtube.com/watch?v=Vufih-WN5R4
- AOsborn 4y agoI thought this was absolutely the solution but backtracking a little now based on experience so far. We have a two-level, five bedroom new build in Auckland which came with a single-zone ducted system. So outputs are the bedrooms plus upstairs and downstairs lounges. The vents are tidy and unobtrusive - much less space than a wall unit in each location. We're having major issues balancing the temperature across the different rooms as there is one thermostat. Think setting the temperature overnight for one room with a couple plus a cat vs another room with one of the kids. Basically the wife and I are always far too hot because otherwise we're freezing all the other rooms. Or setting a reasonable temperature in the lounge makes all the rooms icy in short time. I'm now thinking about forking out the couple of thousand to get a small heat pump installed directly into our room so we can run it separately from the rest of the house. So if building from scratch, either look into a multi-zone system or separate heatpumps. If you can get separate systems but hidden in the walls/roof that would be the best.
- dahfizz 4y agoI had a similar problem, but I decided that simply running the fan to mix up the air was a fine solution. The fan doesn't use much electricity, and it's good not to let rooms get too stale anyway. I have the fan programmed to run 10 or 15 minutes an hour regardless of if the heat pump needs to run. It keeps things pretty even.
- throwawaylinux 4y agoCan't you choke down the airflow from your bedroom duct?
- TedDoesntTalk 4y agoWhat about in-line duct fans or even register fans in the rooms that are not heated/cooled appropriately: https://www.amazon.com/AC-Infinity-Register-Thermostat-Control/dp/B0792QR5YT/ref=asc_df_B0792QR5YT/ https://www.amazon.com/AC-Infinity-Register-Thermostat-Contr... Appropriately placed In-line duct fans and register fans will pull the heated/cooled air where you want.
- thedougd 4y agoHave checked the ducts for dampers? They're often installed where the duct branches. It's not unusual to find they're not balanced well or the locking screws have loosened allowing the dampers to move on their own.
- radicalbyte 4y agoHow much electricity was the fan using? :)
- rootusrootus 4y agoIndeed, sounds like a problem with the fan. My 3000sf house uses 1100W for the fan, and about 4000W for the heat pump. I expect converting to mini-splits would increase, not decrease my overall power usage.
- _benedict 4y agoPretty sure mini splits are significantly more efficient today, with SCOP of above 5, so that seems unlikely?
- fifteenforty 4y agoThis unit runs at about 5
- rootusrootus 4y agoI recently replaced my [central, ducted] heat pump, and the new one is rated with a 4.981 SCOP. It's fairly efficient, but not the most efficient on the market.
- fifteenforty 4y ago-40% for the duct heat loss
- rootusrootus 4y agoThat seems kind of high for insulated ducts, where does that number com from?
- fifteenforty 4y ago
- throw0101a 4y ago> Ducts are dead. Ducts are still needed to circulate air, especially if you want to remove stale air (e.g., bathrooms, kitchen) and bring in (filtered) fresh air (to bedrooms).
- kccqzy 4y agoNot being snarky but why don't you just open the window for that? I have a CO2 detector that I believe is a reasonable proxy for stale air. When it goes above 1000 I simply open the windows. By the time I remember to close the windows the reading is almost always below 500.
- krageon 4y agoA ventilation system allows you to filter (not a luxury when you live in a big city, where you will be breathing pollutants otherwise) or perform some thermal magic if the outside air is very cold (or very warm), by running the outflow and inflow pipes really close to each other.
- jwcooper 4y agoWhere I live, it can get very cold. Not always very efficient to open windows for 5 months out of the year. A great option for keeping CO2 levels down in a house is with an HRV (or ERV) [1] that will heat the fresh air coming in to cycle it throughout the house. [1] https://en.wikipedia.org/wiki/Heat_recovery_ventilation https://en.wikipedia.org/wiki/Heat_recovery_ventilation
- thadk 4y agoThere is an open source 3D printable unit design here which I installed in my window and works well for relatively efficiently exhausting the CO2 from one person in cold weather: https://www.openerv.org https://www.openerv.org (license: CC BY-NC-SA 3.0) I did not 3D print mine, but ordered it, though as an early adopter, adjustment was required.
- 4y ago
- jimmaswell 4y ago> Ducts are dead. How do you move the heated/cooled air into/around the house without ducts?
- fifteenforty 4y agoIt’s a ‘mini split’ in US lingo. There are thin, highly insulated refrigerant lines going between the outside unit and the inside unit. The inside unit exchanges heat with the air. https://www.daikin.com.au/our-product-range/split-system-air-conditioning/alira-x https://www.daikin.com.au/our-product-range/split-system-air...
- jimmaswell 4y agoThat thing's an eyesore compared to a duct to me.
- batiudrami 4y agoMuch like solar panels on the roof (which I have also heard Americans describe as an eyesore), once they are common enough your eyes just slide over them and you don’t notice.
- catiopatio 4y agoI don’t see rooftop solar panels unless I go outside and intentionally look for them. A mini-split system puts an ugly, cheap, plastic wall-cyst within your field of view in every room they’re installed.
- usrusr 4y agoWhy are they plastic wall-cystst though? Wouldn't a manufacturer offering a less obtrusive look (I'm not thinking of fancy boutique, just Ikea grade surfaces) alongside a standard interface for third party options get a huge market advantage?
- 4y ago
- xattt 4y agoSince this is the top comment right now, what is integration with Home Assistant/Hubitat like?
- Brybry 4y agoI don't think the hardware is that expensive in the US, it's the installation (which costs more than the hardware). And mistakes by installers will cost even more. Our installers didn't flare a line set connection properly and it leaked slowly and that was a very expensive bill (especially since refrigerants have changed so much). Our Daikin indoor units have also had condensate leaking issues, probably due to poor installation. Ductless heat pumps do seem like the future but I think there are issues with regards to condensate draining, air filtering, and indoor unit cleaning/maintenance and replacement that could be done much better.
- thehappypm 4y agoDaikon is way worse than Mitsubishi from what my hvac guy tells me
- fifteenforty 4y agoMitsubishi Electric or Mitsubishi Heavy Industries? I sourced opinions far and wide and in the end it seemed to be a coin toss between Mitsubishi Electric and Daikin. A lot of it comes done to parts availability, and both seem very strong in Australia.
- thehappypm 4y agoI live in a cold climate
- toomuchtodo 4y agoMitsubishi is gold standard in cold climates. It’ll pull heat from -30F air.
- EricE 4y agoThere's no reason that's unique to Misubishi. My parents Fujitsu has done so.
- TheSpiceIsLife 4y agoThis is exactly the same setup I have here in Launceston. Another great thing about having three seperate units is if one breaks, rare as it is, you're not stuck without heating / cooling.
- _carbyau_ 4y agoI am leaning more to this solution for this reason. Trying to get any tradie quickly these days doesn't happen. Trying to get an aircon person in an Australian summer is worse. I despair for the rental market right now. High prices and landlords are generally crap at amenities they don't personally use.
- deleted 4y ago[deleted]
- Karupan 4y agoI got a similar setup for my house as well. Being able to selectively cool rooms that are in use is great. However, I do wish the insulation was far better. Unfortunately I’ve noticed that Melbourne houses are usually very poorly constructed due to expensive raw materials and labour.
- fifteenforty 4y agoHave you examined your insulation with a thermal camera? Might be worth your while to get an energy inspector out. Personally I haven’t yet, mostly because I can still see low hanging fruit to fix.
- Karupan 4y agoYea have some pretty obvious improvements pending as well. But that’s a good suggestion - might get someone to come give a professional assessment before I put in a 7kwh unit for another room.
- EricE 4y agoYou don't even need a pro - you can get FLIR cameras that attach to cell phones for around $100 and they are more than adequate to show you areas of irregularity and worthy of targeting. I got one years ago mainly as just something to play with but I use it ALL the time for all kinds of things. Having a thermal camera is crazy useful.
- fifteenforty 4y agoI have a cheap Uni-T thermal camera. It’s great fun!
- IAmGraydon 4y agoAre you asking why the Daikin Alira X is more expensive in the US? It's because it's not a brand that is normally found here. If you went with a common US brand you can get a good system with 4 units and a 36,000 BTU heat pump unit for around $6,500 USD installed. I don't love the wall units - they're pretty ugly, even the new ones. If you're getting a mini-split, the in-ceiling or wall cassettes that are hidden are really the way to go IMO.
- fifteenforty 4y agoCan you give me an example of a comparable model available in the US?
- fifteenforty 4y agoIn the Australian market, the efficiency of the in ceiling or in wall units is lower than the high wall units. They are also much cheaper to buy and install.
- hawaiianbrah 4y agoWow, really? Prices seem much higher than that in Seattle. A friend got 3 handlers totaling 24k BTU for like 12 grand.
- fifteenforty 4y agoThat’s double the price I paid here!
- bthater 4y agoSeems to just be Seattle tax, I had to get a water line replaced in my home and the quotes were $2-7k higher than I've seen suggested in other regions. Tradework here is inflated likely by the salaries of tech workers in the city.
- earleybird 4y agoIn my locale, trades like plumbing (including gas & hvac), drywall, roofing etc range from 1 to 1.5 what contract developers from NTT, IBM et al are billed at. In absolute terms - 110 - 140 for contract devs and trades are often "to busy" at 170.
- tomcam 4y ago> Ducts are dead Great. You just eliminated approximately 15% of lazy screenwriter tropes for thrillers and action movies. Now they are forced to rely on replacing live surveillance camera feeds with a loop.
- red-iron-pine 4y agoNo one is crawling through house ducting
- tomcam 4y agoTELL THAT TO THE LAZY SCREENWRITERS
- monkeydreams 4y ago> In a house I own in Melbourne, Australia Same, and we have just implemented 2 x 7.1kw units along with about 7kwh solar panels. Our heating costs have plummeted and we can survive on days like today (17th Jan) with minimal impact to our comfort. We are looking at changing water heating next as this is now the biggest part of our utility usage.
- PaulHoule 4y agoIt doesn't get that cold in most places in Australia does it? Heat pumps need to be scaled for the maximum heating or cooling load, whichever is greater. The optimal situation is that the heating and cooling loads are similar, but in colder parts of the U.S. the heating load is much larger than the cooling load and the case for the heat pump is not so good as a place where the need for heating and cooling are more balanced.
- yaysyu 4y agoDepends on your frame of reference but in Melbourne it can get to around 1 degree Celcius in winter (33~F). Sometimes subzero but very rarely
- PaulHoule 4y agoIn upstate NY it gets a lot colder than that https://en.wikipedia.org/wiki/Syracuse,_New_York#/media/File:Syracuse_Weather_Statistics.png https://en.wikipedia.org/wiki/Syracuse,_New_York#/media/File... the average temperature is below freezing for four months.
- fifteenforty 4y agoThat actually sounds like a perfect climate for it.
- Zach_the_Lizard 4y agoIn my part of Texas, it gets below freezing on 12 days a year on average, but within the last two years it's been as low as 7F / -14C. I guess that's the value of having a big heat sink, the Pacific Ocean, at your doorstep: temperatures are more stable.
- pxmpxm 4y agoWe have a brand new Daikin VRV system in new york and are currently working on retrofitting a nat gas heating solution - heat pumps aren't a good fit for anywhere north of Atlanta: When it's really cold out (say 25F or below), the heat pump stops for around 10mins to defrost the exterior coils, which means no heat running at all in that period, and this pause happens more frequently the colder it's outside. The end result, our ~1400 sq place took more than 24hrs to heat up from 55F to 72F when we got back after christmas. Also you don't save any money on operating it, even with the efficiency yade yada the cost of electricity will run you more than the equivalent in nat gas. So nothing but downside.
- Winsaucerer 4y agoRegional Vic for me, Daikin Alira X's installed in rooms about a month or two ago, and they've been great. Very energy efficient, and individual units in each room means we can match everyone's preferred climate -- even heating one room while cooling another! Main downside is that you need space for more inverter units outside. They're pretty quiet, too. You can certainly hear the air coming out, but it's fairly quiet and certainly wouldn't be noisy enough to bother you over tv, work, or anything else.
- ace2358 4y agoIt’s going to take a lot of work to get Melbourne homes up to modern standards for heating cooling and insulation!
- malandrew 4y agoThe problem I have with mini splits is that they are an architectural eyesore. Are there any high quality ones designed to be built into walls discretely like cove lighting has done for lighting?
- fifteenforty 4y agoThere are floor mounted units that can be recessed into a wall. Alternatively, ceiling cassettes (not ducts) can be good. https://www.mitsubishielectric.com.au/wp-content/uploads/2022/03/Split_Systems_Brochure-2022.pdf https://www.mitsubishielectric.com.au/wp-content/uploads/202...
- nraf 4y agoHow does it function on a day like today? My evaporative cooler works decently at this temperature but with the side effect of making the floorboards sticky
- tempestn 4y agoDucts are good for indoor air quality though. Keeping our central fan on at low speed all the time significantly reduces measured CO2 in occupied rooms, particularly bedrooms overnight.
- deleted 4y ago[deleted]
- realityloop 4y agoWhich side of the city are you on, could you let me know who you had do the installation please?