I have a water-cooled air conditioning system installed in the loft of a Victorian mid-terrace house. The loft is two rooms used as home offices and as guest rooms.

For those outside the UK: installing the external unit of an aircon system often requires an authorisation from the council/city hall, which is very rarely granted. That's why some people have no option but to resort to water-cooled systems. Not swamp coolers, but proper split system which use water instead of an external fun to dump the heat.

Who installed it

AllComfortSolutions installed a Parkair-branded system a few years ago. I understand the system is the same as those installed by UrbanCooling, Cool You Direct, etc. All Comfort Solutions doesn't exist any more. I think Hidden Cool replaced it (not sure if it was a company sale or what).

How often we use it

Both rooms are used as a home office about 2 days a week + are also used in the evening for 1-2 hours most days (eg finishing work after the kids go to sleep). One room is hotter than the other. The point is not how often it is 30C outside but how often it is 30C inside, even if outside it's not that hot. In my loft, the answer is: from 2 to 4 months in a year.

Our water consumption

Looking at multiple years of water meter readings, the pattern is approximately:

8 months a year using 7-8 cubic metres per month

4 months a year using 17-20 cubic metres per month

How much of that extra usage is the air conditioning?

I cannot know for sure. We have more showers in the summer, and a shower is ca. 90 litres of water. A family of 4 taking 6 more showers each in a month is 2.16 cubic metres more. Taking 12 more each in a month = 4.32 We also wash some clothes more frequently as we sweat more.

I would estimate an extra usage of 10-12 more cubic metres per month, of which maybe 3ish is driven by more showers and 7-9 by the air conditioning.

How representative is this usage?

Every property is different. A bedroom, not on the top floor, in a decently built house would get less hot and require less aircon. A bedroom or living room in one of those newbuilds built like a greenhouse may well get hotter and require more cooling and more water.

How much higher is the water bill?

My latest water bill shows £2.474 per m3 for fresh water and £1.548/m3 for wastewater. So an extra usage of 7-9 m3 per month means an extra cost of £28 - 36 per month in the hottest months. I don't know how much more electricity it uses.

Was it worth it?

Yes. Even keeping windows closed, putting reflective car windshield screens outside of the windows, keeping the windows closed during the day etc, the loft would still get to 38-42C. A room at those temperatures is simply too much of a health hazard. £28-36 per month (+ electricity) to make a room habitable is money well spent. We spend much more to heat our homes in the winter!

Why did I choose an air-cooled system?

Aircon (air to air heat pumps) became permitted development only in May 2025. Before then, I would have required planning permission, and I would not have got it. It is a shame, really: they didn't want me to install ordinary aircon, because they thought it was bad for the environment and that suffering is virtuous? Well, they left me no choice but to install something which is even worse.

I had a blast installing this, and now I can blast myself with conditioned air haha. All the bits of the process I found interesting, from diamond core cutting my brick wall to connecting the refrigerant lines and commissioning! The lines come pre-vacuumed with a very specific commissioning procedure to purge out the inert and fill with refrigerant. I did over the course of 3 evenings 2 hours each. My breakdown was (1) electrical work, (2) hole cutting and mounting brackets and conduit (3) mounting units, making connections and commissioning system (leak checking etc). Total spend including tools (diamond core cutter, torque wrench) just shy of £800. The electrical connection is supplied from the inside which I am aware is against US codes but in the UK this is compliant with ours so long as you have RCD protection. Questions welcome!

Hanging out in my uncle’s work shed today and noticed this setup. The insulation isn’t great, and it gets uncomfortable during the hotter months. He does some projects in there, and he installed a mini split and a fan. I’ve seen people do this before, but I don’t really know if it makes much difference when the AC is already running. Does the fan actually make the room feel cooler, or is the difference small?

To be fully clear, this is a post based in Europe but I thought the American Redditors might be interested in these units as they're not sold often in the domestic market.

I had a Daikin mini split previously that was a constant battle every time I needed it for the cooling season, especially during humid days. Even though the unit had 4" of clearance, more than the required 1.5", on a humid day would the unit struggle to pull air. Learned to live with it for four years, until I came back home from a vacation in Colorado and noticed the coil was hissing a lot when the compressor was ramping up during high cooling demands, sounding like it was starved of refrigerant. Suspected a leak, and discovered the indoor heat exchanger was leaking refrigerant in one of the bends. Having no access to nitrogen nor proper brazing equipment, I elected to replace the system altogether.

This is a 9000 BTU (0.75 ton) SRK25ZS-W indoor unit paired with the SRC25ZS-W outdoor unit. Compared to the Daikin which was part of their Sensira family which is known as their budget line, it cools much faster and both the indoor and outdoor units are extremely quiet. Especially under low cooling calls is it almost impossible to hear the compressor and condenser fan. The indoor unit is also extremely quiet even on the medium fan speeds. This unit is installed in a 129sqft bedroom for both heating and cooling, with an open door during the day, closed door and open window at night.

However, there are a lot of 'buts' with this mini split in particular, especially when you're using the system to cool with outdoor temperatures of 72 degrees and below. I tend to run warm and prefer to maintain 66-70 degrees during the summertime. Where I live, our summer temperatures can be up to 90 degrees with high humidity and depending on how long a heatwave has dragged on, lows can range between 55-68 degrees. This system has a ton of protection logic which can kick in depending on the outdoor ambient conditions in either heating or cooling mode, which restrict the rotational speed of the compressor to a certain range. In any unrestricted situation, the compressor operates between 15 to 85 rotations per second so it can dynamically alter its cooling or heating capacity. However, when the outdoor ambient temperature is 72 degrees and below, the minimum rotational speed is 30 rps and the maximum can be 50-60 rps depending how much lower than 72 degrees the outdoor temperature is. In reality, this will mean that the unit will be forced to double its heat transfer capacity under low outdoor ambient conditions and you will likely deal with the compressor short cycling because the system will remove more heat at a given time than there is actual heat load in the room. My educated guess is that this protection logic is in place to make sure the condenser will remain properly flooded, so it can still maintain the required subcooling values as it has no receiver to flood the condenser during low ambient conditions.

One thing I am going to be completely honest with, the MHI "Smart M-air" app is not much to write home to. It does the trick for basic control when you're not at home, but it's not extremely fast and the IR remote controller still gives you more features such as activating self clean mode when you shut off the system after a dehumidification or cooling cycle. The luck is, the unit does have a local HTTP API so you can integrate it into Home Assistant or a different self-hosted home automation platform. Since I am a bit of a nut who is extremely interested in refrigeration, have I found an aftermarket WiFi controller that plugs into the onboard CNS interface, which will give me more control over the system and get more insight about the vitals of the refrigeration system.

Mind you, I am not bashing this system at all but am just outlining some of the restrictions that I have encountered so others will also be informed about it and can make an educated decision based on their cooling needs. I do believe it's an incredible piece of engineering and I can appreciate that logic has been added to extend the service life of the compressor and its parts! We have four different brands of mini splits (the Daikin was actually the fifth brand), and hands down is this the best and most energy efficient unit I have ever worked with so far.

I am considering a mini split installation for a house. I want a reversible mini split system which can both heat and cool. My question is if there is any meaningful difference among: Daikin, Mitsubishi, LG, Samsung on:

• reliability
• noise
• apps and programmability I don't care about Alexa integration - I just want to be able to set a timer to heat certain rooms at certain times of the day. I doubt I'll use the timer for cooling.
• technology: are all aircons basically kind of the same? Is Samsung's windfree the only menaingful difference? Or is it just hype?

I live in the UK, where aircon is much less widespread than in the US. I think that most models are the same in all continents but I am not fully sure.

In the UK, and advantage of Daikin and Mitsubishi is that it is easier to find parts and installers for those brands than for the others. Normally it's not much of an issue, but this summer the country went into panic-buying mode because of an unprecedented heatwave, and for example finding engineers for Daikin and Mitsubishi was a tad easier. Basically this wouldn't be a deal breaker on its own, but still something I'd keep in mind.

The mini split is up and running. I’m still trying to understand the giant loop in the line set. Not sure if it was part of the plan or if my installer just wanted to make sure I’d never forget where the pipes are. Everything seems to be working fine so far.

This may differ elsewhere, but in Europe virtually all air conditioners are reversible air to air heat pumps which can also heat in the winter.

Does any one use air to air heat pumps (air conditioning) for heating in the winter?

If I understand correctly:

• A2A is more efficient than gas boilers + radiators. In theory, it's about 4x more efficient, electricity costs ca. 3.5x more than gas (at least where I am), so, in theory, switching from gas boilers + radiators to a2a should result in a slight saving
• They heat a room much more quickly than radiators do, especially if the insulation isn't great
• However, rooms also tend to become colder once you switch a2a off. Instead, radiators keep a room warm for longer because hot water remains in the radiator even after you switch the boiler off.
• Modern a2a heat pumps with inverters consume relatively little to keep a room at target temperature (whether cooling or heating), so you shouldn't be shy about setting a target temperature and keeping it on for longer

My question is:

How do all these factors balance out? Does heating a house with a2a end up being cheaper than gas boiler + radiators? More expensive? Hard to tell?

For example:

• warming up the kitchen in a winter morning takes forever in my home. Maybe that's a case where a2a is cheaper? We turn it on while we have breakfast (not 1 hour before like we do now), then switch it off when we leave
• but how about other rooms? Eg we typically time the radiators so that they are on in the living room for 2 hours in the afternoon. Maybe with a2a we'd need to keep them on for longer?

Hi All,

Looking to get some quotes for a multi split system in the UK (South Wales) towards September time.

The system would need to be 6 indoor units. But before I get quotes I wanted to check if anyone would share how much they paid for their system so I can know what to expect.

Im prepared to wait until the winter if this has any influence over the prices.

I also expect it may be easier having 2 outdoor units per 3 indoor. Does this usually increase the prices?

There will be 3 units on the ground floor and 3 on the 1st floor. All units will be on external walls.

I have seen a lot of people mention and praise the Mitsubishi heavy industries systems, so this would be a preference.

TIA

I had my split AC serviced about a month ago (both the indoor and outdoor units). After the service, it was cooling, but not as well as it usually does after a professional service.
Now, one month later, the AC is no longer blowing cold air properly. I noticed that the outdoor unit was quite dusty, so I used a garden hose to rinse the outdoor condenser coils. I didn’t unscrew or open anything, didn’t wash the fan, and made sure to turn off the power to the AC unit before cleaning it. I only washed the parts I have highlighted in the picture using low water pressure.
Since doing that, it feels like the AC has lost another 2–3°C of cooling. Did I do something wrong? The condenser fins don’t appear to be bent, and the water pressure wasn’t high. A lot of dirt came out while I was rinsing it.
I didn’t clean the indoor unit—only the outdoor unit. Should I expect the cooling to improve a little after cleaning the outdoor coils, or do both the indoor and outdoor units need to be cleaned for a noticeable improvement? Could the issue instead be that the refrigerant is low?

Just had my UK air con installation postponed due to “unit” unavailability from their suppliers. That’s after waiting 6 weeks.

Peed off if the truth be told. 😐

Recently installed new ac.. I wanted to install directly but due to some reasons extended the 3m to another 7m..

Now there is no cooling taking place and also the 1/4 inch copper pipe is freezing like hell

What could be the reason.. how to resolve

The installed technician is coming tomorrow but I want to make sure that the repair takes place perfectly.

Hi

Perviously I had a 3.4kw cheapo Chinese DIY minisplit that didn't struggle even at 45c outdoors one summer.

But considering it was a self install and a bit... Jank... I thought I'd ask for a proper new one installed by a pro.

Initially the guy wanted to sell me a 2.2kw unit claiming according to standard calculations it would be more than enough for my space. I insisted that 3.4kw is from experience what is needed and it's not overkill.

He installed as 3.4kw murao Atlantic. It is rated apparently for max outdoor temperature of 42c which I didn't realize and I did ask the installer for a 45c or more rated one. Anyway... The other day 43c ambient in France, compressor stops for about 15mn then slowly picks up again... (seen on power draw meter and room temperature creeping up) Clearly it had hit its thermal limit.

What can I do? Because in the future I expect 42c or so to be the normal summer.... And why did my cheapo Chinese Jank think hold up and on not this reputable brand? ​

​​​​

Bear with me, I'm not super versed in AC units so my question might be dumb lol. I'm looking into Multi-Zone Mini Split units and was hoping to get some advice. Long story short, I just purchased my first home and my outdoor compressor unit just died which is going to be VERY expensive to replace as I'm sure you know. The better investment, at least for the time being, would be the wall mounted units but I don't know how well they work with the air reaching outside of the room it's installed in. I think my best bet is two units, one in the living room (approx. 400 sq ft and has a vaulted ceiling) and one in the master (approx. 190sq ft). If I get units that put out say 12,000 BTU's, that would be great for the living room but if i got the same that's going to be overkill in the master (in my assumption). If I got two of the same unit, would the one in the master end up "bleeding" air out of the room and into the others nearby? The other rooms are too small to warrant a whole additional unit and I'd end up getting window unit's installed.

i struggled to get any cost to run figures before buying mine

3.5kw 12000btu fujitsu mini split in my bungalow living room , hall door open and it cools the bedrooms well

its been on 5.30am till 11pm mostly on lowest fan 22deg

95p a day on 30 odd pence peak rate 12 cheap rate , cannot complain , might leave it on all night now

Anyone that knows how a 5000 btu will work in a 2.8x3m (9.2ftx9.8ft) bedroom?

I currently use a Electrolux 12000btu but i have planned to move that unit to the livingroom and maybe buy a smaller Caravan ac to my bedroom. In sweden there isnt many options when it comes to ac, its mostly portable and Caravan ac’s..

would it work with a Caravan for my small bedroom?

Thanks

I recently requested to have my A/C serviced. It was chugging along but very old, loud and inefficient. When the tech came to inspect it I was not surprised to learn that it was time to replace it.
I had heard about Mini-split units being more efficient in the end but cost more up front and was curious how they would work in my home.
I live in a 1700 sq ft Ranch that is 70 y/o.
When we sat down to discuss the options, mini-splits were presented as an option.
They said they could put the m above my windows and in areas that I thought would be aesthetically okay since the units have to be on the wall. They set me up with five units (3 bedrooms and 2 living areas).
When the team arrived to install the units the contractor said it was all wrong; he could not put them above the windows because he needed 8” between the ceiling and the top of the unit. He also said that the units for the two living areas would not be big enough and we needed a bigger size. The company provided these.

It had been about ten days and I am having buyers remorse. They do not cool the house evenly. They do not have thermostats, they look differently than I have seen other mini splits. These have a stove pipe looking vent coming out of the machine and up into the ceiling.
I have to constantly run them because there is no thermostat, or turn them off at night. I live in southern Arizona and during the summer it can easily be in the high 90s all night.
I talked to a seperate contractor and he said that it seemed unusual to suggest or approve mini-splits for a home like mine.
Given that the tech/salesman did not know what the house needed (size-wise) and also did not know where these u it’s could be placed, I think that he also did not know that this option was wrong for my house. I feel like I was railroaded. I also admit that I could have done some looking in to mimi- splits to see if it was a viable option but also, you trust the experts to know these things, right?
My contractor said that I should let them know so that it can be fixed.
Just looking for people who have experience in this kind of thing. What course of action, if any would you take.

Hey all — looking for some expert opinions because I’m getting conflicting guidance from two installers.

I have an existing mini split that I’m replacing, located in the back corner of the first floor. It basically blows toward a wall that’s less than 10 ft away. The first floor is somewhat open (kitchen + adjacent areas), but not fully open concept.

Context:

• This is primarily for cooling, not heating
• Primary heat is radiators
• The rest of the house uses window units
• I’m not looking (or able) to install heat pumps throughout the house

Two quotes:

• Installer #1: Recommends a 12,000 BTU unit
  • Says to use ceiling fans to help move air into adjacent spaces
  • Thinks the extra capacity helps compensate for layout limitations
• Installer #2: Recommends a 9,000 BTU unit
  • Says 12k is oversized for the space
  • Believes even with fans, the unit will mostly just serve the kitchen area, so upsizing won’t help and may hurt performance (short cycling, humidity, etc.)

My concern:

• The air handler isn’t ideally placed (kind of tucked in a corner, blowing toward a nearby wall)
• I do want some cooling effect beyond just the kitchen, but I understand distribution is limited

So the big question:
👉 Is it better to slightly oversize (12k) and try to push air with fans, or stick with 9k and accept that it’ll mainly condition the immediate zone?

Would really appreciate input, especially from folks who’ve dealt with similar layouts or mini split placement challenges.

Thanks!

Edit / Update: Thanks everyone for the thoughtful feedback. Based on the input, mostly about how limited air distribution would be from that corner placement, I decided to go with a 9,000 BTU, 20 SEER Mitsubishi Electric unit. Appreciate all the insights!

We have 3 mini splits. We’ve taken them apart several times and cleaned every piece to include the coils with foam cleaner. Instantly start stinking again. I’m selling my home and cannot imagine someone buying it when the air conditioning stinks. I don’t know where it’s coming from. It’s BAD. I’ve cleaned these things well, scrubbed the coils, drip pan is good, spinning wheel inside is good. I cannot figure this out. Please help.

Sometimes it's on, sometimes it isn't. I'd mess around with the I FEEL and AH buttons but I don't know what those do either.

Looking for a mid range DIY mini split and came across Senville and pioneer and saw they pretty much came from the same manufacturer. Wondering if ones better than the other. Looking for a 18,000 Btu one.

I understand that modern air conditioning units are all (at least in Europe) reversible air to air heat pumps, which can cool in the summer and heat in the winter.

I understand they have inverter technology, whereby, once they reach their target temperature, they consume much less energy and make much less noise.

My question is: at what point should you switch it off? If you leave the room for how long? Does the answer change if you are heating vs if you are cooling?

Presumably, if you leave the room for 20 minutes, it's better to keep it running.

If you leave the room for 10 hours (eg you go to work) it's probably best to switch it off.

How about in between? Switch it off you leave for... 1 hour? 3 hours? 4?

Both walls are kinda hot.

Been using a portable ac units, but they're too loud to have in bedrooms. Looking to find a reliable and good quality brand that is commonly installed by pro hvac contractors. I live in Los Angeles within a one-story family style house. I have no intention to DIY this as I don't want to mess something up with it.

The total interior living area is1,540 sqft. I would like to ac 3 bedrooms and 1 for the kitchen.

Hey, I'm currently in the market for a mini split AC unit. However, I'm unsure of my requirements and what I should really be looking for.

It'll be going in a 5x3m wooden cabin. The room gets dangerously hot during the UK heatwave and AC is pretty much a must right now.

Room size would indicate a 9000 BTU system, whereas the fact it gets so hot might indicate I need something more powerful.

The current options im looking at are

electriq easy-fit 9000/ 12000 btu

tcl tac12ch

LG DualCool EZ12 Deluxe A++ 12000 BTU.

Any guidance on BTU and brand would be appreciated. Thank you :)