Strained HVAC unit, Pippin Brothers, Lawton, OK
March 11, 2013

Pippin Brothers Home Services happily services the Greater Lawton, Fort Sill, and Duncan, Oklahoma area. If your house is uncomfortable; wasting energy; has plumbing problems or if you want to avoid breakdowns or verify everything in your home is working as it should, give us call at 580-699-5662. We've already helped many of your neighbors, and would be honored to help you.

Imagine for a moment that you’re jogging. But instead of breathing normally, you have to breathe through a straw.

Sounds crazy, right? Trying to force so much air through such a small opening would easily tire you out--and even cause some health issues if you did it every day.

Well, that’s what it’s like when you have undersized supply and return ducts. Except the adverse effects are a strained HVAC system, inadequate comfort, higher energy bills, breakdowns, expensive repairs and possibly even a premature end to the life of your equipment.


Well, before we get into that, let’s talk about the purpose of your ducts and vents.

What are supply and return ducts?

In order for your HVAC system to heat and cool your Lawton-area home, it needs a way to deliver the air.

It uses your supply ducts to deliver the heated or cooled air to the supply registers or diffusers that are located in several rooms.

Then the return grilles allow the air to return to the furnace or air conditioner where it is heated or cooled again. The process repeats until your room’s temperature reaches what’s set on the thermostat.

If the supply duct is too small or the register is too restrictive, your furnace or air conditioner has to blow longer and harder in order to heat your home. It’s like blowing out through a straw while jogging. It would take more time strain and effort to get all the air out.

If the return duct is too small, there are an inadequate number of return grilles or they are undersized, it can’t return enough air to recirculate back into the system. The average duct system has 25% less return air than required according to National Comfort Institute. Again, it’s like if you were breathing in through a straw while jogging. You wouldn’t have enough air to circulate back into your body (think oxygen deprivation). You’d hyperventilate, and your body would shut down.

This poor airflow not only makes your system run longer than necessary to provide comfort, but increases your energy bill as well. And just like breathing through a straw while jogging over a long period would adversely affect your health, so running your HVAC system for a long time with undersized ducts shorten its life.

Properly sized and installed ducts allow for a natural airflow in your Lawton-area home that won’t put a strain on your system and keep you comfortable and minimize energy bills.

Unfortunately, the typical American home duct system only performs at 57% efficiency according the National Comfort Institute.

Other problems that decrease airflow

Even if your ducts are properly sized, there are other problems that can restrict air circulation as well. These problems include:

  • Blocked supply registers – Don’t place furniture or drapes over your supply vents. They block the air coming out.
  • Dirty air filter - The air filter in your return vent keeps dirt out of your HVAC system, but if the filter becomes dirty, it restricts how much air can get back into your system to be reused. Check your filter at least once a month and change it when it’s visibly dirty.
  • Leaky air ducts - Leaks in your air ducts prevent your HVAC system from transporting all the air to your rooms. These can create hot or cold spots in your home. The average duct system leaks up to 40% of conditioned air according the Department of Energy. To learn more, read our post about leaky air ducts.

Breathe normally

Your body can only exhale what you inhale. Your HVAC system is no different. You wouldn’t breathe through a straw, so why should your HVAC system? If your HVAC system isn’t cooling or heating properly due to decreased airflow, contact Pippin Brothers so we can diagnose what the problem is and fix it.

Pippin Brothers' blog is designed to be the Lawton-area’s go-to source for heating, air conditioning, air quality and plumbing. If you have a question you’d like answered, ask us online.

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