Is a Bigger Air Conditioner Better?

Is Your Sacramento Valley Air Conditioner underperforming?

There are many reasons why your air conditioner may be underperforming.  Your system could be low on refrigerant, your evaporator coil could be clogged, the filter could be dirty, or the air ducts that lead to each room in your house could be damaged or crushed.  These problems can lead you to think your AC is undersized, and you should get a bigger air conditioner.  Today I want to tell you why getting a bigger AC may not be the best idea.

The Owner’s Hunch

Hi, I’m Greg Fox from Fox Family Heating, Air Conditioning, and Solar.  As the Sacramento area grows outward, new neighborhoods have sprouted up very quickly.  After the haste, many folks I’ve talked to have complained that their air conditioner seems to be undersized.  And sometimes they are right!  Sometimes the HVAC contractor that installed that system didn’t consider that the house has 10-foot ceilings instead of the usual 8-foot ceilings.

Doing the Math

That isn’t the only thing we look at either.  In both older and newer homes, the square footage of the house is important.  The type of windows and doors, the orientation of the house, as well as the impact of any trees that might be covering the house are all also important.  And the insulation levels in the house is also important.  All of these factors are used to figure out the proper size for a home’s AC unit.

Summer Heat

If your home’s air conditioner is undersized, you’ll know it because it will just run, and run, and run, even on 85- and 90-degree days.  That’s warm, but nothing compared to the average of 22 days per year of temperatures soaring to 100 degrees or more here in the Sacramento area.  Most air conditioners these days are designed to be efficient to 95 degrees or less.  Anything hotter than that, and EVERYONE’S air conditioner is going to run non-stop.

Going Bigger

This is typical for a lot of the homes around the Sacramento area.  But some people wonder if a bigger sized system is a good idea.  Here are some factors I would consider when considering the move to a bigger system:

Your air ducts are sized for the sized system you have now.  If you get a bigger system you can really affect the static pressure of the system.  Static pressure is like the blood pressure in your body.  If your heart was too big for your body, it could cause complications with your blood pressure, right?  Well it’s the same with the static pressure of your HVAC system.  The bigger air conditioner and its compressor won’t be able to operate under the same comfortable conditions as it would if it was properly sized.  This will lead to early system failures of your new HVAC system.

Comfort

A bigger system is also not going to feel as comfortable for your house.  Humidity isn’t as big a deal out here in California, but in other areas of the country it is.  Either way, the comfortability factor is compromised when you get a bigger system.

Imagine this.  When you turn on the AC in your car on a hot day, the air comes on full blast until you start to feel nice and cold in there.  Now, turn that AC back off, and its starts to feel muggy and strangely warm too quickly.  The car walls, seats, leather and other things in the car haven’t gotten cool yet.  That’s the same thing you’ll experience in a house with too big of a system.

The thermostat might satisfy at the temperature you’re asking for more quickly, but it kicks right back on quickly too.  This can really mess with the humidity levels in your home because the system hasn’t run long enough for it to do its job, which is to cool your house AND dehumidify the house at the same time.  Ideal humidity levels in our homes here are around 45-55%.  Anything more than that and it really starts to feel sticky in there.

Wear and Tear

Another reason to size it right is because now that your larger system is constantly turning on and off all day on these hotter days, the motors will wear out faster.  The most damaging time for a motor, especially your $2000 compressor, is when all that damaging heat and energy slam into that motor to get it running.  Yes, it levels off once its running but the starting and stopping is what really hurts those expensive motors.

The right sized system runs for longer times but cools your house more effectively by getting your walls, your furniture, the carpet and ceilings cool as well as the occupants in the house.  That’s why getting it right is so important.

Get it Right

If you’re an HVAC technician watching this video, don’t just go into the house and say, “Oh yeah you’ve got a 2.5-ton system in your house, so that’s what we’re going to go back with.”  You MIGHT BE going back with that same size system, but at least know for sure that’s what size your customer needs by doing a proper load calculation of the house and its surroundings.  An HVAC system is one of the most expensive things people buy for their homes.  It would be devastating to buy too small of a system or too large of a system.  You want to really get it just right!

Case in Point

I just went to a family’s house in the Natomas area.  Lots of newer homes have been built in this area.  This home had a 3.5-ton system on a house that I measured out at 2300 square feet.  This 3.5-ton system is too small for this house.  This was a house that had two thermostats, also known as a house with two zones, or a zoned house.  It uses one thermostat upstairs and one downstairs.

Zones

Zoned houses are designed to cool one floor at a time rather than the whole house.  Watch my video on “How to Cool a Two-Story House” for a better strategy on cooling this house, linked at the end of this blog post.  Basically though, I just set the schedule on their thermostat (which had never been set up before) to cool the downstairs living area during the day, and the upstairs sleeping areas starting around 7pm.

These folks were told by another company before mine to just set it to their desired temperature, which was 74 degrees, on both floors and press the HOLD button on the thermostat.  That’s why when I went into their home to give them an estimate for a new system, they were really focused on getting a bigger system; because that 3.5-ton system just could not keep up with that big house all day.  The temperature in the home was climbing throughout the hot days.

Each zone was only about 1300 square feet.  But they had 12-foot ceilings, 20-year-old vinyl, south facing windows, a south facing wall that is getting hammered by the sun all day, AND those walls are a part of the main living room downstairs and the master bedroom upstairs.  They can literally feel the heat radiating through their walls into those rooms. And they typically have some activity during the day upstairs, especially around the afternoon hours.

All this was taken into consideration as I advised them that the size of their system could be reduced by a half a ton, but considering everything about the house, the 3.5 ton would be just fine.

In Summary

Getting a larger AC than you need might sound appealing, but it’s torture on your new system.  It probably won’t last as long as it’s supposed to, and you’ll be buying a new system sooner than you should.

I hope this blog post has helped you understand the importance of not getting an oversized air conditioner for your home.  If you have any opinions on this topic, please feel free to comment below.  We really appreciate your input!

Thanks so much for stopping by, and we’ll see you on the next blog post!

Don’t miss our video on a related topic:

 

 

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