What size of Air Conditioner do you need?

Bigger is not better. The Facts:


Have you ever walked into a large department store or supermarket in the early opening hours to do some shopping on a hot day expecting to get some cool relief ? In most cases it would feel uncomfortably cold and clammy. The feeling would be noticeably different if you returned later in the day when the store was full of customers and heat producing equipment had been running all day.


The reason for this is that the air conditioners are sized so that they would still provide enough cooling during the highest heat loading conditions. Air conditioning is not called “Air Cooling” because the comfort that is produced comes from a combination of:


· lowering the temperature (Cooling) and

· reducing or removing humidity (Dehumidifying).


The senior generation and snowbirds that migrate to Arizona or Texas will all say that the dry conditions are more comfortable. Most people will feel just as comfortable say at 25c (77f) with the humidity under control at 50% that at 22c (72f) with the humidity at 70%.



An Air Conditioner removes humidity by capturing droplets of condensate water from the warm room air as it passes over the Evaporator cooling coil. This removal of moisture can only take place while the air conditioner is running. What will happen if an air conditioner is oversized is that the unit will cool the space down too quickly and cycle off without removing much moisture. Since the thermostat only reacts to temperature there would be no way to make adjustments to correct the resulting problem with high humidity.

As a rule of thumb, we say that on the hottest day of the season (say 30c), a properly sized central Air Conditioner should be running close to 50% of the time and as much as 75% during the late afternoon hours.


The old curbside method of “Guestimating” tonnage to size Air Conditioning is 800 Sq’ / ton . This of course needs to be adjusted to consider the following:


1. Bi-level and 2 Story homes compared to a Bungalow

2. Year of construction/ insulation values

3. Windows and south facing exposure

4. Number of occupants and heat producing appliances

5. Lifestyle. Frequency of opening windows and doors. Expected recovery time


So as you can see Bigger in this case is certainly not better. An experienced HVAC comfort advisor will take the guesswork out of choosing the proper size of Central Air Conditioning for your Winnipeg home.


Call Tradesman today for a complimentary Heating or Air conditioning assessment for your home. 204-888-2020

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