Frosted Evaporator Coils Can Affect the Efficiency of an HVAC System

October 25, 2017


Having regular maintenance on your HVAC system can prevent frost from accumulating on the evaporator coils.

HVAC maintenance

As the weather becomes colder the frosted evaporator coils start restricting the airflow and can reduce the HVAC efficiency. This is a common problem faced by the building owners and managers. Frost is the root cause of many HVAC issues.

When the temperature in the evaporator coil becomes lower than the dew point and dew collects on the surface of the coil, it does not pose a problem. But when the temperature reduces further and goes beyond the freezing point turning dew into frost it reduces the airflow and can cause a a major HVAC problem.

Types of Frost

The initial layer of ice which forms on the evaporator coil is thin and is not harmful. In fact, it is conducive for the functioning of the HVAC. It increases the evaporator tube’s surface area.

The subsequent layers of ice are more snow-like or crystalline depending on the temperature of the evaporator, humidity and airflow. They are known as hoar frost or radiant frost. They reduce the heat absorbing capacity of the evaporator.

Indications of Diminished Airflow

  • Low Levels of Head Pressure – The heat load is reduced and the refrigerant in the evaporator coil fails to vaporize when there is diminished airflow. So there is low condensing pressure.
  • Discharge Temperature is at a Lower Level – If the liquid refrigerant does not evaporate it can go through the coil and enter the compressor. This can lead to wet compression. The discharge temperature may also become low. This is an indication of diminished airflow.
  • Low Level of Condenser Splits – Low levels of condensing pressures and temperatures will lead to low levels of condensing splits. There will be no need for the condenser to raise its temperature to reject the minor heat load.
  • The Compressor Crankcase is Cold – The compressor may get flooded because of the low heat and there may be some liquid refrigerant in its crankcase. Due to this the crankcase may frost or sweat and become cold.
  • Suction Pressures Are at a Low Level – When the heat load is reduced in the evaporator coil the vaporization rate of the refrigerant also reduces. This lowers the vapor pressures.
  • Amp Draw is Higher Than Normal – The refrigerant which comes from the suction line has a higher density when it does not vaporize fully. So the compressor has to work harder and the amp draw is higher than normal.

Importance of Regular HVAC Maintenance

HVAC accounts for nearly 40 -70% of the energy bills of commercial buildings. It is possible to reduce 20% of the energy bills by scheduling a regular maintenance plan. Proactive maintenance measures can prevent frost from accumulating on the evaporator coils. They can also solve the problems of diminished airflow.

HVAC Maintenance St Louis

Scott-Lee Heating Company offers Precision Maintenance Agreements for customers who want to keep their systems running at peak performance. When your heating and cooling equipment runs efficiently, you save energy. Save energy and you will save money too.

Call us today at (314) 200-0788 or fill out our online contact form.