Unit Struggles to Meet Temperature

"I had my 3 ton unit checked the summer because it was behind in the hot weather. They said it was fine and now it is still behind when it is 75 degrees outside, what is the problem?"

First, if it is 95 degrees outside and you are doing at best 75 degrees in the house, it is doing what it is supposed to be doing. Once it gets to 100 and if you are doing 80 in the house then it is doing what it is supposed to be doing. In this area about 20 degrees cooler inside than the temperature outside means that the unit is keeping up and doing what it can do because of the heat and humidity.

Now, in October when it is 75 degrees, it should be keeping up with that cooling temperature inside the house. There is a problem. It could be one of three things. It could be the unit which was checked out, that could be a problem. It could be the air distribution, which is the duct system that could be the problem. It could also be the envelope which is the home that could be the problem. You need to have a professional to look at all of this but especially the unit.

What you could do yourself is to go check that duct system in the attic or under the house. We dug in to this questions deeper and he thought the duct system was in the attic and he thought he was losing some cooling that way. When they do a load in the house, on that system, duct loss in the attic for heat gain is calculated. That calculation is different than if it was in the crawl space because obviously you have more of a heat load if it is in the attic vs the crawl space. That should be factored in to the sizing of the unit, equipment, and the duct system so that shouldn’t be a problem. Get someone to check your unit, you can yourself look at the duct system, make sure no runs have fallen down, there are no holes where an animal or something got into it, you can look at all of that yourself.

Also you have to look at the envelope, the home itself, to make sure you have insulation in all spots because what we have seen happen to in an attic we will take an infrared gun and we take the temperature of the ceiling and it will be 75, 75, 80, 80, 102. You will know that you need insulation over there that is why it is so hot. Check those three things. If it is not the duct system, if it is not the home, then it is the unit. When you look at all three of them that factors in to why you are having a problem, especially with a home that has not had this problem previously. Hopefully you have lived here a few summers or at least the summer before and not had this problem. If it is a brand new problem then it is probably the duct system, or the unit, if it is something that has always happened then I would look at all three.

People will want to think that if they are having a heating or cooling problem then it is just the unit. It could be the duct system, it could be the house, or it could be all three that have a problem or it could be just one of the three have a problem. One of those three being off is going to cause you to not be comfortable. 

Your friend in comfort and energy savings,

Derek Cole

Derek Cole is the General Manager of One Hour Heating & Air Conditioning?, an independently owned and operated franchise based in Laurinburg, North Carolina since 1953 and named to the Inc. 5000 fastest-growing private companies in 2016. He has more than 15 years of experience in the HVAC industry and has created two You Tube broadcasts, The Comfort Experts and #AskDerekCole, filled with tips and tricks on saving energy and being comfortable. He was named the Top 40 under 40 in the HVAC industry by the News magazine and featured in Entrepreneur Magazine Franchise Player Spotlight. Derek has also been seen on CBS, FOX, NBC, ABC, Huffington Post, and Bloomberg Business sharing about One Hour Heating & Air Conditioning? and home comfort tips.