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Troubleshooting Guide: Frozen HVAC Coils

by | Sep 25, 2020

Have the HVAC coils in your commercial building frozen? Use this as a guide to troubleshoot and determine the root cause of the freezing event.


*Note each end-user sets ATC programming logic as they see fit. Situations will vary from coil to coil. The following list reviews the basics in determining the root cause of coil freezes and can be used as a troubleshooting checklist.* 

// Failure of Preheat Coil:

When a preheat coil fails to warm up the frigid outside air coming into the AHU the air can reach vulnerable coils causing them to freeze, bulge and split. If you suspect your preheat coil has failed check the following potential issues:

If your AHU utilizes a steam preheat coil:

  • Steam PRV or control valve failure
  • ATC failure
  • Blockage inside the steam or condensate piping
  • Loss of steam pressure from source (i.e. boiler, campus energy, etc.)

If your AHU utilizes a hot water preheat coil:

  • Hot water supply temperature should be between  120°F-180°F, designed leaving water temperature should be well over freezing temps
  • Check that the preheat hot water system has the proper GPM flow rate and pressure
  • Ensure the preheat coil is not air-bound – air vent if necessary



// Failure of Freeze Stat:

Customer-installed freeze stats sometimes fail to shut down the fan above the freezing point.

  • Check the set point of the freeze stat
  • Investigate freeze stat control circuit to make sure it is powered and functioning properly

// Rooftop AHUs / RTUs

If outside air enters a side panel door on a rooftop AHU, frigid outside air can bypass the preheat coil and cause coils to freeze.

  • Make sure all side panel doors are closed
  • Check that no insulation has been removed from side panels
Split Frozen HVAC Coil and Freeze Block Coil

The Best Freeze Protection

Even with safeguards in place on a standard coil, mechanical failure, human error, and extreme weather conditions can allow freezing air to reach vulnerable coils causing them to freeze, bulge and split.

Until now better technology for freeze protection was unavailable. For superior HVAC coil freeze protection consider replacing critical coils with Cooney Freeze Block Coils.

Coil Freeze Plugs vs Freeze Block Coils

Coil Freeze Plugs vs Freeze Block Coils

Learn about your coil freeze protection options! In this blog, we examine Freeze Block Coils & Freeze Plugs comparing their effectiveness, maintenance requirements, flood risk, lifespan, durability, and warranty coverage. Keep reading to determine which option is best suited for your facility’s specific needs. Don’t miss out on expert guidance from our team; book a call today to explore the benefits of using Freeze Block Coils. Make an informed decision now to avoid costly repairs and potential facility damage caused by freezing events in the future.

Smart Coil for Critical Facilities

Smart Coil for Critical Facilities

For facility managers overseeing mission-critical operations, ensuring the highest level of protection against freeze damage is paramount. Cooney Smart Coils offer an easy and effective solution, compatible with both new air-handling units and existing HVAC systems. Whether you’re undertaking a new construction project or need to replace a damaged coil, Cooney’s Freeze Block technology offers unparalleled protection without compromising the system’s efficiency or capacity. With expert guidance available to help select the best coil for your specific needs, upgrading to Smart Coils is not just a smart choice—it’s a strategic investment in your facility’s operational integrity and longevity.

Maximizing HVAC Performance with Replacement Coil Upgrades

Maximizing HVAC Performance with Replacement Coil Upgrades

Upgrade your HVAC system’s performance and efficiency with energy efficient replacement coils from Cooney Engineered Solutions. Our knowledgeable experts will guide you in selecting the best coil for your application, saving on energy costs and prolonging the lifespan of your equipment. Say goodbye to traditional methods and consider our innovative Freeze Block technology for optimal coil freeze protection


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