HVAC 102

Drew Carr   February 24, 2016   Comments Off on HVAC 102

Air Conditioning, Heating

If you’re reading this, there’s a good chance that you’re not an expert on HVAC.

That being said, you most likely use (and pay for) HVAC every day, so knowing how it runs and what that means for your monthly bill is important. We sat down with Robert Lee and James Bagby of Fox Service Company to talk about two key terms you should remember for maintaining your HVAC. As it turns out, HVAC is a science.

FOX 0229 1


One term to remember is BTU. BTU stands for British thermal unit. Equal to about 1.06 kilocalorie, the BTU is the unit used to equate the energy output of your HVAC system. By understanding how your system uses BTUs, you can both sound smarter when talking about your HVAC, and also save yourself a lot of money.


In HVAC terms, a ton is equal to 12,000 BTUs. So the 5-ton system we mentioned in HVAC 101 hardly means an A/C unit that weighs 10,000 lbs—in this case, it’s a system with an output of 60,000 BTUs.

“A 5- ton system is 60,000 BTUs. Mr. Homeowner has one, and says ‘When I first moved in, my electric bill was 300 dollars and now it’s 500 dollars,’” says Lee. “So I can do a BTU output on the system, and say ‘Mr. Homeowner you’re only doing 48,000 BTUS. You’re only getting 4 tons worth of work instead of 5. You’re still spending the money it would cost for 5 tons, but you’re only getting 4. That’s why your electric bill is so high.’”

Fox 0229 2


Another term to remember is EER, which stands for Energy Efficiency Ratio. By knowing this term, you can get an accurate gauge on your HVAC system’s operation, and better understand what HVAC technicians are talking about.

“Let’s say it costs $1 for 10 BTUs, the output of the A/C system,” says Lee. “That is a 10:1 ratio, and in our world, that’s EER.”

Lee explains that while EER may start off in a good place, it can drop over time.

“So when the A/C is brand new and running great, we have a 10:1 ratio. 10 BTUs for $1. Then let’s say it gets dirty, or the refrigerant charge gets out of whack, or they forget to change the filter,” says Lee. “Now, we’re still spending $1 dollar, but instead of 10 BTUs we’re only getting 5. So now, to get the same 10 BTUS they would have to spend $2. So it’s twice as inefficient.”

It’s this drop in efficiency that not only effects your EER, but your wallet.

“In the summertime, during the hottest part of the day, the house absorbs more BTUs than the air conditioner can remove from the conditioned space, so it runs nonstop,” says Bagby. “What EER boils down to is the amount of energy you are using to run the air conditioner vs. the amount of heat your system is actually removing in BTUs from your home.”

Much like in HVAC 101, the key is maintenance. Lee says a good rule of thumb is to plan ahead.

“You get to work, you work 10 hours a day, you fight Austin traffic all the way home, you get home,” Lee says. “Do you want it to be 105 degrees in your house? That’s why we do A/C checks before the season.”

By checking out the A/C unit or heating units before the season, you can save yourself time, energy and best of all money.