Selecting a Ductless Mini-Split Unit for Your Home

If you’re considering a new HVAC system for your Toronto area home, a mini-split system is tough to beat. With the help of inverter technology, these systems are highly efficient and only generate enough heating or cooling to meet your specific temperature needs. However, in order to utilize this efficiency while staying cool in the summer and warm in the winter, you need to select the right size unit for your home.

Why is Choosing the Right Size Ductless Mini-Split Unit So Important?

The wrong size mini-split unit can seriously hinder its performance. A correctly sized unit, on the other hand, will be able to effectively and efficiently heat or cool your entire home. So, how do you know which size to choose?

When selecting a ductless mini-split HVAC system, it all comes down to the BTUs. Installing a system with a BTU rating capable of meeting your needs and home’s specifications is a must.

What is a BTU?

BTU stands for British Thermal Unit. Used to measure thermal energy, one BTU has enough power to increase or decrease the temperature of a single pound of water by a single degree Fahrenheit.

As far as BTUs and HVACs go, the larger the space, the more BTUs you’ll need. Ductless mini-split units come in a wide-range of BTU ratings. Some are rated as low as 6,000 BTUs, while other units are rated up to 56,000 BTU.

On a side note, keep in mind that the heating capacity of a mini-split unit should be slightly greater than its cooling capacity. It’s also important to avoid choosing a system that is too big for your space. This will ensure optimal performance and save you on cooling and heating costs.

The Pitfalls of an Undersized Ductless Mini-Split:

  • Higher utility bills
  • Increased wear and tear
  • Inadequate heating or cooling power
  • Cold or hot spots

You may save some money by going with a smaller mini-split unit, but it will cost you in the long run. For starters, it will run constantly, resulting in higher utility bills and increased wear and tear. You’ll also experience cold or hot spots due to the unit’s inadequate heating and cooling power, so your comfort will be affected as well.

Bigger Isn’t Always Better

All that said, a larger mini-split with a higher BTU rating isn’t always the best choice. In addition to costing more, which pretty much cancels out any energy savings it might offer, an oversized mini-split will result in short cycling.

As its name suggests, short cycling is when a mini-split system turns off and on repeatedly for short periods of time. Similar to an undersized unit that runs all the time, a larger, short cycling mini-split unit will cause added wear and tear. This can lead to malfunctions, repairs, and premature failure.

To top it all off, an oversized ductless mini-split prone to short cycling will also create a more humid environment. Since mini-splits dehumidify the air while heating or cooling it, one that is constantly turning off and on will not be able to do so properly, resulting in added humidity and dampness.

How to Size a Mini-Split the Right Way

When deciding on a ductless mini-split HVAC unit for your home, it’s important to consider the size of a room or rooms for single or multi-zone configurations. Since the rooms in your home are likely sized differently, the air handlers for each zone of your home will likely have different BTU ratings. The compressor on the outside of your home should be able to complement each indoor unit.

Now, as far as actual sizing goes, a professional HVAC technician will be able to help you determine the right size mini-split for your needs. To get an accurate estimate of the mini-split size(s) needed, he or she will perform the following steps:

  1. Measure the Square Footage of Each Room
    A professional will determine the square footage of each room measuring each one’s length by its width and multiplying the two figures. So, if a room is 35 feet long and 25 feet wide, the formula would look like this: 35 x 25 = 875 square feet.
  2. Determine the Approximate BTU Rating
    For an approximate BTU rating, the HVAC professional will multiply the room’s square footage by 25. So, for an 875 square foot room, the formula would look like this: 875 x 25 = 21,875 BTUs. This simple calculation works best for rectangular shaped rooms. However, not all rooms are rectangular – some are circular, triangular, and so on.

A professional technician can help you determine the right size mini-split for any room configuration. Therefore, before you get out the protractor and measuring tape, it’s a good idea to give your trusted local HVAC technician a call.

Mini-Split BTU Sizing Chart

Area Size BTU
150 to 300 sq. ft. 6,000
300 to 500 sq. ft. 9,000
400 to 650 sq. ft. 12,000
500 to 800 sq. ft. 15,000
600 to 1000 sq. ft. 18,000
800 to 1,300 sq. ft. 24,000
1,000 to 1,650 sq. ft. 30,000
1,200 to 2,000 sq. ft. 36,000
1,400 to 2,300 sq. ft. 42,000
1,600 to 2,650 sq. ft. 48,000
1,850 to 3,100 sq. ft. 56,000

Factors to Consider for Ductless Mini-Split Sizing

While room size plays a significant role in selecting the right BTU capacity, there are other factors to keep in mind as well. External factors, like environmental conditions, also play a role in determining the size of the unit you will need.

If you’ve ever lived through a Canadian winter, then you know all too well how indoor temperatures can be affected by the outside climate. However, did you know that where you live affects the size of the mini-split you need. For example, if you live somewhere with summer temps that regularly reach 90+ degrees Fahrenheit, you will need to increase the BTU rating of your mini-split unit by 30 percent or more.

Ceiling Height
When it comes to heating and cooling, ceiling height plays just as large of a role in the performance of a mini-split as square footage. The higher the ceilings, the more air there is that needs to be heated or cooled. Most homes have eight-foot ceilings, but if yours are higher, you should increase the BTU capacity of the mini-split you buy by a minimum of 20 percent.

Age of Your Home
Another factor to consider is the age of your home. Due to evolving technology and revised building codes, newer homes are typically better insulated than older homes. If you have an older home with poor insulation, you will need a ductless mini-split system with more power to keep it comfortably cool or warm. If this is the case, you should increase the BTU rating by 30 percent or more. On the other hand, if you live in a newer home with better insulation, it will require fewer BTUs.

Other Factors
Some other factors to consider when calculating your home’s required BTU capacity include:

  • Sunlight: Direct sunlight can heat up a room in a hurry. The more direct sunlight a room receives, the higher the BTU rating it will need.
  • Doors and Windows: Since doors and windows aren’t insulated and have cracks and gaps, they allow air to leak in. Therefore, the more doors and windows there are in the zone where your mini-split will be located, the greater the required BTU capacity.
  • Lightbulbs: Most people don’t think about lightbulbs when determining the size of their mini-split, but lightbulbs generate heat. Furthermore, some types of lightbulbs generate more heat than others.
  • Kitchen: Stoves and ovens also give off heat. If you want to install a mini-split for your kitchen or a neighboring room, you may need a larger mini-split with a higher BTU capacity.
  • Flooring: Carpet offers better insulation than hardwoods or tile. While the type of flooring in your home doesn’t play as large of a role as the other factors above, it is still something to keep in mind.
  • Size of Your Household: Last but not least, people also generate heat and can play a role in sizing your mini-split unit. You need to consider the number of occupants who will be spending time in the room where your mini-split will be.

Determining the size of the mini-split needed for your living space is a process commonly referred to as load calculation. Everything we just discussed goes into this calculation, allowing you to determine the amount of cold or warm air needed to consistently keep an area at a comfortable temperature.

While you can perform these calculations yourself by using this guide or any number of load calculators available online, it’s best to contact an HVAC technician for a professional consult. An experienced, well-qualified local mini-split technician will help ensure you install the exact unit for your home’s needs. Articles

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