Air conditioner advice

[BigNick]

Having been renting for the past 12 years, Mrs BigNick and I have taken the plunge and bought an apartment on the Spanish island of Mallorca.

It gets hot here - 90s F and high humidity every day in summer. Plus although the winters are not very cold, the apartment has minimal insulation and currently no central heating. We plan to put oil radiators in the bedrooms.

For the main room we are looking at a split A/C unit with 3.5KW (12,000 BTU) capacity, which can also act as a heater. The installer has proposed us three models, from Fujitsu, Mitsubishi, and Midea (which is a little cheaper, being a less famous brand). I have asked him for the exact model numbers so I can compare features, but... what features should I be looking for? We Europeans tend to have very little experience with air conditioners!

 

[NW-Bound]

You will want one with an inverter compressor, but it is most likely all these units are already of this type. Americans still have relatively cheap energy, so do not want to pay for higher efficiency and these units are not common here.

For example, a Fujitsu 1-ton unit (12,000 BTU/hr) I saw sports a SEER of 29. That means it draws an average of a little more than 400W. Astounding!

See: https://www.inventorairconditioner.com/blog/faq/what-is-the-inverter-technology-in-air-conditioners

 

[Jerry1]

I always consider noise. If I am thinking of the right units, the compressor is outside so that noise won't bother you, but may bother your neighbor. They also have a fan for the unit on the inside of the house. That fan's noise would be one of my main considerations.

 

[euro]

I always consider noise. If I am thinking of the right units, the compressor is outside so that noise won't bother you, but may bother your neighbor. They also have a fan for the unit on the inside of the house. That fan's noise would be one of my main considerations.

I agree - and yes, the compressor is outside, but each interior room unit does have a fan. And they CAN be relatively noisy (especially in bedrooms). Most do have several fan settings, but it's definitely something to keep in mind if you are a light sleeper

 

[samclem]

I have asked him for the exact model numbers so I can compare features, but... what features should I be looking for? We Europeans tend to have very little experience with air conditioners!

I have no experience with these units, but there are two ways that air conditioners can heat a home:
1) as a heat pump
2)Using "resistance heat" (also called "heat strips," "emergency heat" etc)

As a heat pump, the AC unit basically operates opposite as it does in summer--the compressor runs, but instead of moving heat from inside your home to the outside, it moves outside heat (in the air) into your home. This is a very energy efficient way to make heat, saving a lot on electricity. Unfortunately, it doesn't work well when the outside air gets very cold (approx below 30 deg F). That might not happen very often on Malorca.

Resistance heat: This is what you are probably used to with electric room heaters (and how your oil radiators will work--it's just resistance heat that warms oil. They may be more comfortable and quieter than a cheap hot-wire-and-fan room heater, but they are not more efficient). In the indoor portion of the AC unit, resistance "heat strips" are activated when heat is needed, and they make warm air that the regular AC fan blows into the room. Even units that are heat pumps often include resistance heat as a back-up for days when it is too cold for the heat pump to make heat. It costs a lot of electricity, but if it is cold enough and rare enough you might not care.

So, to compare apples-to-apples, see which of the AC units also function as heat pumps in the winter. Maybe they all do. If not, you'll have to do some calculations to see how much money the heat pump function might save you on Malorca.

Does the apartment already have AC (i.e. are you considering these new units just to have central heat in the winter)? If so, if any of the AC units you are considering makes heat only using resistance, it won't be any more efficient than your oil radiators. OTOH, if it has a heat pump function, it will be cost less to heat your home that way than using the oil radiators (but will be noisier outside, since your compressor and outdoor fan will need to run even in the winter, at least until temps get too cold for the heat pump to function).

Congrats on the purchase! Gonna have to change your signature line!

 

[BigNick]

You will want one with an inverter compressor, but it is most likely all these units are already of this type. Americans still have relatively cheap energy, so do not want to pay for higher efficiency and these units are not common here.

We pay around €0.25 for a kWh of electricity, so running costs are important.

The guy who is proposing to do the installation pasted only a little info about each model. The Midea says it has inverter technology. I presume the others do too, and that they are also all heat pumps for heating, but I will ask.

For example, a Fujitsu 1-ton unit (12,000 BTU/hr) I saw sports a SEER of 29. That means it draws an average of a little more than 400W. Astounding!

This is very good news. I was envisaging spending nearly €1/hour for 3.5 kW, which would rack up a large bill pretty quickly.

I always consider noise. If I am thinking of the right units, the compressor is outside so that noise won't bother you, but may bother your neighbor. They also have a fan for the unit on the inside of the house. That fan's noise would be one of my main considerations.

The compressor will be on our balcony, which is separated from our neighbour's balcony by a wall and 15 feet. So this should be OK.

Does the apartment already have AC (i.e. are you considering these new units just to have central heat in the winter)? If so, if any of the AC units you are considering makes heat only using resistance, it won't be any more efficient than your oil radiators. OTOH, if it has a heat pump function, it will be cost less to heat your home that way than using the oil radiators (but will be noisier outside, since your compressor and outdoor fan will need to run even in the winter, at least until temps get too cold for the heat pump to function).

No, there is nothing at the moment. The previous owners of the apartment (a retired couple) lived there for 30 years with no AC and no central heating - just fans and (I guess) kerosene or portable electric heating.

Average daily high/low temperature in January is 40F/60F, so we should be OK. Orange and lemon trees grow in the public parks.

Congrats on the purchase! Gonna have to change your signature line!

Yes, we hope to be moving permanently in 18 months or so. Mrs BigNick is applying for French nationality (post-Brexit), and for some strange reason France likes you to still be resident in the country when you swear allegiance to it. Fortunately my grandfather had the good sense to be born in Ireland in 1888 and so I have been able to get an Irish passport (by right) already.

 

[explanade]

One thing I see outside the US are these room air conditioners typically mounted high, just below the ceiling.

You get a remote control to change the speeds and even have some kind of oscillating effect.

But there don't seem to be ducts. They're often mounted on interior walls, meaning it's not ducted to the outside like the window mount units which were so common in the US back in the day.

I searched for them but couldn't really find them in the US. However, Amazon lists some portable units that you can roll from room to room.

I have central air but I'm thinking of something like this just to use in one room at a time. Must use a lot less electricity than to cool down the whole house.


Oh and Mallorca is beautiful.

 

[NW-Bound]

One thing I see outside the US are these room air conditioners typically mounted high, just below the ceiling.

You get a remote control to change the speeds and even have some kind of oscillating effect.

But there don't seem to be ducts. They're often mounted on interior walls, meaning it's not ducted to the outside like the window mount units which were so common in the US back in the day.

I searched for them but couldn't really find them in the US. However, Amazon lists some portable units that you can roll from room to room.

I have central air but I'm thinking of something like this just to use in one room at a time. Must use a lot less electricity than to cool down the whole house...

Yes, you can buy them in the US, even though they are more popular in Europe and in Asia. The reason is that they are easy to retrofit into a home that is not originally built with a duct network for a central AC system.

They are called mini split ductless AC, and consist of an interior air handler that you saw, and a compressor that is mounted on the wall outside, or ground mounted. Two copper lines are used to port Freon from the compressor to the interior blower and back. A hole is drilled through the wall for these Freon lines and the electrical control cable linking the air handler and the compressor.

Because there is no duct, each air handler serves only one room or area, but there are now multi-zone systems where the compressor will pump Freon to multiple air handlers.

 

[NW-Bound]

Here is a quad-zone ductless system.

 

[explanade]

Ah way more complicated to install then.

 

[NW-Bound]

The multi-zone system will require freon lines running to each room. That's the price to pay if you do not have a built-in duct network.

On the other hand, a single-zone mini-split AC is not too tough for DIY. A small system will also run on 115VAC instead of 230V, and may not require a new electrical line as it can be tapped into a nearby circuit.

 

[NW-Bound]

By the way, for a free-standing portable AC make sure you buy a dual-hose unit.

The single-hose units exhaust hot air out the window by ejecting air from inside the room. This means it creates a vacuum inside the house, and that causes exterior hot air to get sucked in through cracks in the walls and around doors.

A dual-hose unit sucks in outside air via the inlet hose, heats it up with the heat extracted from the room, then exhausts that hot air via the outlet hose.

Heat is easily created with electricity, such as with an electric heater or on a stove top. Heat cannot be "destroyed", and can only be exchanged or moved from one medium to another. Hence, to cool a room you need to expel that heat, and an AC needs to have a heat exchanger to heat up the outside air while cooling the inside air.

 

[meierlde]

In fact I have thought about how one would retrofit AC into houses in the north that had hot water heat, (no ducts or chases). The minisplit would be the way to go there. since retrofitting ducts would be a mess to do. (Both the house I grew up in and one of my grandparents houses had hot water heat, so that an AC retrofit would have been complex, in northern in and southern mi)

 

[explanade]

I read a brief blurb about the recent heatwave in the Northwest.

I think it was either Portland or Seattle had only a small percentage of homes with AC.

If they get heatwaves up there regularly, there could be a huge business for AC installs.

 

[Bamaman]

Mini Split HVAC units are going to be the future of heating and air conditioning. They're incredibly quiet both inside and outside. Since they have inverter compressors, the outside unit only runs as fast as required to provide the cooling to the inside evaporator. The cost of running a 12,000 btu unit will be very little if it has an EER of 29--even at electricity rates twice that of juice in the U.S.

There are brand names like Mitsubishi and Fuijtsu can get expensive. Even off brand heat pumps are often made with the same components (like Mitsubishi compressors) and they perform comparably. Mini Splits don't require incredibly huge factories to make them, and they're built in just about every country in the world.

I've been looking at a 12,000 unit on Amazon, and they're coming in about $800 for the offbrand unit. A name brand unit might run $1100-$1200. That doesn't include installation. They're easy to install other than the electrical work to the Mini Split. You just have to use a vacuum pump and then cut a valve on to get the precharged coolant into the system.

I think I'm going to be using an Amana brand PTAC unit like those used in many hotels. They're about $900 and are easier to install for the one room. No professional heating guy will be required. (I'm flipping the house with a 20' x 20' den.)

 

[explanade]

Where do they hide the external part? I never see big banks of AC components like you do in the US.

 

[samclem]

Where do they hide the external part? I never see big banks of AC components like you do in the US.

They are there. Sometimes on a roof, sometimes "out back", and frequently in an alley, suspended on brackets affixed to an external wall --and about 4 meters above the street

 

[NW-Bound]

The mini-split compressor is small (it is usually only 12,000 BTU/hr), so is easy to mount or hide outside the house.

 

[meierlde]

Note that minisplits come in sizes up to 42000 btu per hour (at home depot for example). If you compare a 36000 minisplit to a standard central ac unit is is much smaller, more nearly the size of 20 or so years ago (units have gotten bigger to put bigger coils in to improve the SEER of a one speed compressor.) (The unit my house in Houston came with in 1976 was 1/3 the height of the final unit i replaced it with in 2000 or so) I think the minisplits by having a variable speed compressor, eliminate the need for huge coils. In particular the units with multiple inside units (up to 4) need variable speed compressors because at least some times only one inside unit would call for heat and cool and full bore that could freeze the inside unit up. Note today you only get the variable speed on top of the line ducted systems.

 

[NW-Bound]

...For the main room we are looking at a split A/C unit with 3.5KW (12,000 BTU) capacity, which can also act as a heater...

You will want one with an inverter compressor, but it is most likely all these units are already of this type. Americans still have relatively cheap energy, so do not want to pay for higher efficiency and these units are not common here.

For example, a Fujitsu 1-ton unit (12,000 BTU/hr) I saw sports a SEER of 29. That means it draws an average of a little more than 400W. Astounding!

We pay around €0.25 for a kWh of electricity, so running costs are important.

This is very good news. I was envisaging spending nearly €1/hour for 3.5 kW, which would rack up a large bill pretty quickly...

12,000 BTU is 12,660,672 Joules.

So, 1 ton of AC capacity or 12,000 BTU/hr is 12,660,672/3600 = 3.5 kW as you noted.

However, in order to remove heat at the rate of 3.5 kW, the AC does not consume 3.5 kW, but a fraction of that. The exact ratio depends on the temperature differential between indoor and outdoor temperatures. Hence the definition of SEER (Seasonal Energy Efficiency Ratio) which is measured by testing under different temperature scenarios then taking a weighted average to represent an "average" climate.

The result is a very simple to use formula

Average Power Usage(Watt) = Cooling capacity (BTU/hr) / SEER

So, that wonderful Fujitsu AC can remove heat at the rate of 3.5 kW using only 12000/29 = 414 W. This is unbelievable a few years ago. And I just saw a model with a SEER of 33!

And that means your power consumption for AC will be only 1/8 of what you were prepared to pay. Cheers!

Here in the USA SW where the temperature hits 110F+ (43C) routinely in the summer, I would not expect the unit consumption to be as low. However, it should burn electricity at 1/3 the rate of units of yesteryear with a SEER of 10.

 

[BigNick]

The result is a very simple to use formula

Average Power Usage(Watt) = Cooling capacity (BTU/hr) / SEER

So, that wonderful Fujitsu AC can remove heat at the rate of 3.5 kW using only 12000/29 = 414 W. This is unbelievable a few years ago. And I just saw a model with a SEER of 33!

And that means your power consumption for AC will be only 1/8 of what you were prepared to pay. Cheers!

If I've understood your definition of SEER, it seems that the number is a bit confusing, because it includes the actual efficiency ratio (around 8) which is then multiplied by the BTU-to-kW factor. That also probably explains why I have been seeing "EER" quoted on the (entirely metric) specifications that I've been reading...

 

[deadhorse]

To determine the size of A/C needed, the general rule of thumb is: 1000 BTU's, will cool a BUT, as big as a TUB.

 

[LastOfTheBoomers]

We installed a Mitsubishi GL 18K last December - they offered a rebate for the model with a heat pump - we weren't planning on getting that option - and we didn't know if we would use it since we have a standard boiler system in our condo.
I was amazed how efficient the heat is - no noticeable bump in the electric bill.
The outside unit is very quiet - and the fan slows down per demand.
The inside unit has a quiet mode that is really quiet.
Our condo is about 1,100 sq feet - the unit is in the living room - and cools into the bedroom - if you leave the door open. The unit can be aimed to blow down the hallway into the bedroom- this is key if you only install one unit.
Expensive - but works very well.

 

[NW-Bound]

If I've understood your definition of SEER, it seems that the number is a bit confusing, because it includes the actual efficiency ratio (around 8) which is then multiplied by the BTU-to-kW factor. That also probably explains why I have been seeing "EER" quoted on the (entirely metric) specifications that I've been reading...

It is not mine, but the definition of the industry. Yes, it includes the conversion factor to go from BTU/hr to Watt.

If the ratio of energy usage to heat transfer is computed using the same unit for both, then the dimensionless ratio is called COP (Coefficient of Performance).

SEER = COP * 3.41214

SEER is EER averaged over a range of outdoor temperatures to approximate a chosen standard climate. SEER for a unit is usually higher than its EER.

For more, see: https://en.wikipedia.org/wiki/Seasonal_energy_efficiency_ratio, which also mentions the European Seasonal Energy Efficiency Ratio (ESEER).

 

[NW-Bound]

There's one more thing I would like to add.

Because energy usage varies with operating conditions, the old EER was measured at 95F (35C) outside temperature, and the inside return air of 80F (27C).

Now, I live in a place where it routinely gets above 110F (43C) in summer midday, and in order to have the interior temperature at 78F (26C) my AC return air is at 70F (21C) or lower. So, my AC would not be operating at its advertised EER.

And then, the SEER (Seasonal EER) is even higher than EER. In short, these numbers are good for comparing different units, but I was too optimistic in thinking that your new AC will draw only 400W, let alone in a place like mine.

By the way, my highest daily energy usage this year was 120 kWh one day in late June when the highest temperature was 122F (50C). I barely got back from a European heat wave that saw 96F (36C) in Paris, and 99F (37C) in Lyon. My AC is a 5-ton unit (60,000 BTU/hr), and I do not remember what its EER was.

PS. My lowest daily usage is about 22 kWh/day (when the AC/heat pump does not run). So, the max AC usage is about 100 kWh/day in the hottest day. Thankfully, it is usually 60 kWh/day in the summer.