Why It Happens

When cold outside air meets warm, moist exhaust air inside the core, the exhaust can drop below 0 C and ice forms. Left alone, ice blocks the channels and destroys effectiveness.

Common Solutions

• Defrost bypass - periodically send warm supply air through the exhaust side to melt ice.
• Preheat - warm the incoming air slightly before the core so exhaust stays above freezing.
• Recirculation - mix a little return air into the intake during extreme cold.
• Frost-resistant core - wider channels and hydrophobic surfaces slow buildup.

Which to Pick

For most commercial systems a timed bypass or a small preheat coil is enough. The right choice depends on how cold your winter design temperature is.