How to Extend the Life of Your HVAC Equipment – This Summer and Beyond (Part 1)

Michael W. Dickenson, P.E., CFEI

For most of us, seasonal maintenance on our home’s HVAC system is not a priority.  The majority of homeowners use their HVAC system until a component fails. Understanding the basics of how our home’s HVAC system functions can help us to prioritize our HVAC maintenance.

Some results of diligent seasonal maintenance yield:

  • Reduced equipment run times which increase mechanical equipment lifespan.
  • Reduced energy usage which can mean decreased energy bills.
  • Regular checks aid in preventing equipment downtime and can avoid uncomfortable scenarios.

In general, the HVAC system in our home circulates air that has passed the conditioned space.  Most HVAC systems in residential applications are either split-type units, or self-contained packaged units.  Both types of units contain similar components, such as the supply air fan, evaporator coil, and condenser coil.  Split-type units consist of an indoor piece of equipment as well as an outdoor piece of equipment, whereas the self-contained packaged units are an all-in-one unit located outside. Regardless of whether the HVAC system is a split-unit, or a self-contained packaged unit, a supply air fan is the device used to move the air to be conditioned.  In the cooling season, the supply air fan moves the air across the evaporator coil where moisture from the interior, conditioned spaces is removed in liquid form, known as condensate.  The result is cool, dry air which is passed back to the conditioned spaces.  The thermostat, located within the conditioned space, tells the system when the conditioned space is satisfied, which de-energizes the unit.  With the goal of extending equipment life, reducing energy costs, and preventing unwanted downtime, it is important to understand the following.

Return Air: Fight Premature Wear on Your HVAC Unit 

The term return air often refers to the air that has absorbed moisture from the interior, conditioned spaces and is upstream, or before the cooling coil.  The cooling coil is a series of intricate tubes and fins which, when in contact with the return air, results in water condensing on the cooling coil.  Gravity then carries the water to an internal drain pan where it is disposed of.  Dirt and airborne particles are removed from the return air to prevent a build-up on the cooling coil.  A build-up on the cooling coil would increase equipment run times and, in some cases, can cause premature wear.  Therefore, the best defense against a build-up of dirt and particles on the cooling coil is to ensure the particles are filtered.  The method of filtering the dirt and particles from the return air, in most cases, is with the use of a return air filter which resides within the return air grille.  The filter captures any dirt and particles.  The first line of defense against premature wear is to ensure the return air filter is changed-out at proper intervals.  The interval of change-out will depend on the household.  For example, a household with multiple occupants and pets may require a filter change-out each month; whereas, a household with a single occupant might require a return air filter change-out every three months.  With the ever-increasing popularity of smartphones in our lives, setting alarms/reminders aids in maintaining the required filter change-out period.

Cooling & Condenser Coils: Optimize Your HVAC Unit Run Times

Some integral components of an HVAC system include the cooling coil (evaporator) and the condenser coil.  For purposes of this section, we will focus on equipment operating in cooling mode (summer).  The cooling coil is the component which transfers heat from the conditioned space to refrigerant.  On occasion, even with regular return air filter change-outs, the cooling coil (evaporator) will accumulate dirt and debris.  As a result, the equipment must operate longer to satisfy the conditioned space temperature (sometimes referred to as setpoint).  The increased equipment run times take place due to a reduction in airflow passing over the evaporator.  A good maintenance practice for homeowners is to have the evaporator coil cleaned prior to the start of each cooling season.  The cleaning process, performed by a qualified technician, consists of evaporator cleaning by means of approved chemicals.  Due to the fragile nature of the evaporator, care must be taken to use the manufacturer-approved chemicals.  In addition, the evaporator fins may be cleaned by using fin combs.  It should be noted, the appropriate fin comb for the evaporator must be used to prevent damage to the fins.  In most cases, the chemical cleaners will remove built-up dirt and debris, allowing the dirt and debris to drain out the condensate drain piping.  

Note:  Dirt and debris must be removed on the upstream side of the evaporator coil; dirt and debris must never be forced through the evaporator.

The outdoor portion of the HVAC system, known as the condenser, rejects the heat to the outside.  The condenser contains a condenser coil.  The condenser coil may also accumulate dirt and debris, and must be cleaned by a trained, qualified technician.  A common mistake is to clean the condenser coil with high-pressure water; this will damage the condenser coil.  Like the evaporator, the condenser coil is fragile, and care must be taken not to bend or damage the coil fins.  A qualified HVAC technician will use approved chemicals on the condenser coil, then if needed, use low-pressure water to remove dirt and debris from the inside out.  Dirt and debris must never be forced through the condenser coil as this will damage the coil.

In general, the recommended intervals for evaporator and condenser coil maintenance are on an annual basis.  Diligent maintenance ensures the equipment functions by design and does not operate longer than required.  Reducing run times leads to reduced energy costs and improved overall equipment life.

In Part 2, we will continue the discussion of How to Extend the Life of Your HVAC Equipment when we talk about components and their functions of HVAC systems, as well as good maintenance/service practices.