When it comes to keeping your place temperate during the hot summer months, air conditioning can go a long way. Portable air conditioners are a great choice if you’re looking for something versatile – as they can easily be moved from one room to another.
For the best results, it’s important to choose an air conditioning unit that’s the right size for the area you want to cool. However, it can be quite daunting to know what unit to buy if you’ve never ventured into the world of air conditioning.
How Do Air Conditioners Work? A Simplified Explanation
Air conditioners work by converting a substance called a refrigerant from a liquid to a gas and back to a liquid again in ongoing cycles. The concept behind this is that, as the refrigerant becomes a gas, it simultaneously absorbs heat from its environment. It only takes some basic chemistry knowledge to understand why this happens.
Energy is required to convert a liquid to a gas. As more energy is introduced, particles in a substance start to move around more freely, further away from each other, causing the energized substance to convert from its denser liquid form, to its lighter gaseous form.
Using water as an example, you can touch and feel water much more easily than steam or water vapor in the air, that’s because the water particles are more closely stacked when water is in its liquid state (water), as opposed to its gaseous state (steam).
To convert water to steam, you have to boil it, which is a process that involves heating it up. As the particles absorb the thermal (heat) energy, it’s converted into kinetic (movement) energy and they start to move around more freely from one another, which is why the water is no longer as dense and why it converts to a gas.
In the same way thermal energy (or heat) can be used to convert water to steam, heat can also be used to convert refrigerants from their liquid state to their gaseous state.
But refrigerants are different from water in that they don’t need as much heat to convert to a gas. Refrigerants can get enough heat to convert from liquid to gas simply by absorbing heat energy from the environment. In this way, refrigerants get the energy to convert to gas by “stealing” heat energy from the hot air, which is why they cool the air.
Air Conditioner Coil and Fan Systems
To cool down the air in your home, air conditioners make use of a fan and coil system. The coils are a tubing system that contain the refrigerant substance. When hot air from your home moves over these liquid-filled coils, the liquid refrigerant inside the coils “steals” the heat energy out of the air to cool it down. A fan blows this cold air out of the air conditioner system into your home, which cools your place down.
However, the cycle needs to repeat continuously in order to be effective. To make this possible, the now gaseous refrigerant needs to be converted back into a liquid so the liquid refrigerant can be used to cool down more air.
To get the gaseous refrigerant back into its liquid state, a compressor is used. The compressor works by adding so much pressure to the gaseous refrigerant substance, it condenses into a back into a liquid. However, when converted back into a liquid, the refrigerant releases the heat energy it absorbed when it became a gas back into the air around it. If this hot air is released back into your home, the air conditioner will be completely ineffective, so another fan is used to blow the hot air outside instead of releasing it back into your space.
How Do Portable Air Conditioners Work?
Portable air conditioners do everything a normal air conditioning system does. Like any other air conditioner, portable air conditioners work by cooling the air with coils that are filled with refrigerate, blowing the cool air inside and then “moving the heat” by blowing hot air outside.
Because of this, it’s important to note that a portable air conditioning unit has to be located in an area where it can dispel hot air outside. Most portable units are made to be placed in front of windows, so as to vent out hot air outside through the window. However, there are also portable air conditioners made specifically to vent through fireplaces or even holes in the wall.
If you’re looking to cool down a space such as a basement, which has no windows or any other place where hot air can be vented out, it’s important to consider this before buying a portable air conditioner. You might be able to find a workaround which still allows the portable unit to be fitted so it can release hot air outside, but you’d have to plan this before buying the unit to avoid disappointment.
What Is BTU?
BTU stands for British Thermal Unit and is a measurement system used to rate the cooling or heating capacity for aircons, heaters and even fridges. In simple terms, it’s a measurement system that measures the ability of an appliance to change or regulate temperatures.
One BTU is the energy required to heat up one pound of water (1lb) one degree Fahrenheit (1°F) at sea level. When measured as energy, a BTU is about the same as 1055 joules.
Choosing the right BTU for your space is easy when installing a permanent central air conditioning system, seeing as your HVAC contractor will probably know how to calculate your BTU requirements.
When buying a portable air conditioner, however, things are a bit trickier. The BTU you need to cool a down a space efficiently will vary, but two of the most important factors to consider when deciding on BTU is the size of the space you’re trying to cool, as well as how much heat the space naturally has.
It goes without saying that bigger spaces require units with a higher BTU. You might also notice that some rooms in your house with bigger windows are naturally warmer because they get more sun. Kitchens can also tend to be hotter, seeing as using your oven or stove will release heat into the room.
When working with a fixed space, choosing the BTU is straightforward, but to get the most out of a portable unit, it has to be versatile so you can use it in different rooms of different sizes that naturally receive different amounts of heat from the sun.
Choosing the Right BTU for Your Portable Aircon
There are a few BTU calculators online that can help you establish the best aircon unit size based on the space you want to cool. However, these calculators aren’t necessarily the only thing you should go by when choosing a unit.
Some factors to consider when buying an aircon unit include:
- The insulation of the space you want to cool: A room with more windows will require more BTU’s than one consisting of mostly thick walls
- Desired temperature decrease: If your desired temperature is close to the climate outside, you’ll need less BTU’s
- Ceiling Height: If your ceiling is higher you’ll have more space to cool, requiring more BTU’s for every square foot
- Space shape: An open space with a lot of air between walls will be more efficient to cool than a narrow space, as airflow in narrow spaces is restricted. Running a fan to promote airflow can improve this problem
- Roofing color: Darker roofing absorbs more heat, requiring more BTU’s to stay cool
Seeing as you’ll want to move your portable aircon unit around, you’ll have to consider the average size, warmness, insulation and other factors of the spaces you want to cool. In cases where the room size and natural heat differ a lot from one space to another, you’ll have to compromise.
The guidelines for BTU’s per hour vs the square footage of the space you want to cool is as follows:
- 100-150 square feet: 5000 BTU
- 150-250 square feet: 6000 BTU
- 250-300 square feet: 7000 BTU
- 300-350 square feet: 8000 BTU
- 350-400 square feet: 9000 BTU
- 400-450 square feet: 10 000 BTU
- 450-550 square feet: 12 000 BTU
- 550-700 square feet: 14 000 BTU
To give you an idea, bedrooms can vary from 100 to 220 square feet. So depending on the size of your bedroom, it could take 5000 to 6000 BTU to cool.
Why Choosing the Right BTU is Important?
There’s no definite way to choose the right BTU for a portable air conditioning unit, as the best unit will depend on your personal requirements and the different spaces you want to cool. The bigger the difference in size and natural heat of the different rooms you want to cool, the more difficult it will be to choose a unit with the right amount of BTU’s.
The Problem with BTU Overload
Choosing the biggest portable air conditioning unit possible with the largest amount of BTU’s definitely isn’t the answer. A unit that’s too big will quickly cool the air to your desired temperature. Once the air is cooled, the unit will switch off to avoid cooling the air even more. Without the unit running, the air will start to heat up again, causing the unit to kick back in again and do another cooling cycle.
This constant cycle of cooling the space quickly, turning off and then kicking back in a while later for another short cycle, shortens the lifespan of your portable aircon unit, as the compressor responsible for condensing the gaseous refrigerant will soon give in.
Not Using Enough BTU’s
Conversely, a unit that doesn’t have enough BTU’s for the space you want to cool will never stop running. Even though the unit will be running non-stop, your room temperature might not be as low as you set to aircon. This is because the unit might simply not have enough cooling power to reach your desired temperature.
When the unit is constantly running with no periods of resting in between cycles, the lifespan of your portable aircon unit will also be shorter.
With summer on the way now is great time to invest in a quality aircon unit. By following guidelines and consulting professionals help, you can choose the best portable air conditioning unit for your space