When summer hits Chilliwack and the temperature climbs past 30, your first instinct is to want the biggest, most powerful AC unit you can afford. Bigger has to be better, right? More cooling, faster relief from the heat.
It does not actually work that way. An oversized AC is one of the most common installation mistakes we see across the Fraser Valley, and it causes real problems. Here is what is actually going on, and why proper sizing matters more than raw cooling power.
What "tons" actually means
AC units are measured in tons. One ton equals about 12,000 BTU per hour of cooling. A typical Chilliwack rancher might need a 2.5 to 3 ton system. A larger two-story home might need 4 tons. The number is supposed to match your home's actual cooling load, not be picked from a brochure.
Cooling load depends on a bunch of things. Square footage matters, but so do ceiling height, window area, sun exposure, insulation quality, the number of people in the home, and whether you have got an open-concept layout or lots of closed rooms. A 2,000 square foot home in Sardis with great insulation and small north-facing windows needs less AC than the same square footage in Promontory with big west-facing windows that catch the afternoon sun.
A proper load calculation walks through all of that. It is called a Manual J calculation in the trade. Any qualified HVAC company doing an install in Chilliwack should run one before they recommend a system size. If a contractor quotes you a system based on square footage alone, get a second opinion.
What goes wrong when AC is too big
This is the part most homeowners do not expect. An oversized AC actually performs worse than a properly sized one. Here are the four problems we run into the most.
First, short cycling. A too-big AC blasts your home cold in 10 minutes, then shuts off. Then the temperature creeps back up and it kicks on again. This on-off-on-off pattern stresses the compressor, wears out parts faster, and uses more electricity than a smaller unit running longer cycles.
Second, humidity problems. An AC has two jobs. It removes heat, and it removes moisture from the air. The moisture removal happens slowly, when warm air passes over the cold coil and water condenses out. A small AC runs longer, removes more moisture, and leaves your home feeling drier and more comfortable. A big AC cools the air fast and shuts off before it has time to pull out moisture. The result is a cold, clammy house that feels worse than the temperature would suggest.
Third, uneven temperatures. Big AC units cool the rooms closest to the supply vents fast, then shut off before the cool air has time to reach further rooms. The bedroom upstairs stays warm while the living room downstairs is freezing. A properly sized unit cools more evenly because it runs longer.
Fourth, higher costs. Oversized AC means a higher equipment cost (you are paying for cooling capacity you do not need), higher electricity costs (short cycling is less efficient), and more expensive repairs over time (compressor wear).
What about undersized AC?
Yes, going too small is also a problem. An undersized AC will run constantly during heat waves and still will not keep up. You will see high electricity bills and a house that never quite gets cool.
The honest sweet spot is what the load calculation actually says. Not 10% bigger to be safe, not 10% smaller to save money. Right at the calculated size. Modern variable-speed AC units have a wider operating range, so they can adjust output up and down. With those systems, getting the size right matters less, but it still matters.
What Chilliwack summers actually demand
Chilliwack summers are not Phoenix. Our design temperature, the value contractors should use for sizing, is around 28 to 29 degrees Celsius. That is the peak you should expect to encounter on the hottest day of a typical summer. Going much higher than that in your sizing is wasted capacity.
But our humidity matters. Chilliwack summers can be muggy, especially after summer rain. That makes moisture removal a bigger factor in comfort than raw cooling power. A properly sized AC running long, slow cycles will do more for your comfort than an oversized one slamming cold air at you.
The questions to ask a contractor
When you are getting AC installed in Chilliwack, ask three questions. First, did you do a Manual J load calculation? Second, what is the recommended size based on that calculation, and why? Third, what is the SEER rating and the variable-speed capability of the unit you are recommending?
If the answer to question one is "no, but I have been doing this for 20 years and I can eyeball it," walk away. If they cannot explain question two in plain language, walk away. And if they are pushing a single-speed unit on you without explaining why, ask why a two-stage or variable-speed unit is not a better fit.
We do load calculations on every install. It is not optional. We would rather lose a quote to a competitor who sold the homeowner a bigger unit than install something that will not perform.
Free assessment
If you are thinking about adding AC to your Chilliwack home, or replacing one that has not been working well, call us at (604) 655-6929. We will come out, measure your home, run the calculation, and give you a written quote with the right system size. No upselling, no padded numbers, just a system that actually fits your home.