Static field route #19109

What do I do when a fan coil condensate trap is dry or air-locked and the pan overflows?

Equipment Connections: RTU, AHU, VAV, Fans & Louvers⚠️ CHECK BEFORE YOU FIXV191 answer-gap expansion

📖 Verified core answer

A condensate drain has to overcome unit pressure and maintain drainage. Prime/check the trap, venting, slope, and manufacturer trap detail before water damages ceilings or equipment.

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Field verification checklist

Check if water is standing in the pan while fan is running.
Verify trap depth/layout and vent/cleanout arrangement against manufacturer detail.
Prime the trap if required before commissioning.
Check slope, blockage, and drain termination.
Run the unit and confirm steady gravity drainage.

Ask foreman

The FCU/AHU at [tag] is overflowing because the condensate trap appears dry/air-locked. I checked trap, slope, and venting. Do you want the drain corrected per manufacturer trap detail?

Text to foreman

Route options

AMake the field correction only if it is within your assignment and the approved method.

BHold and document the condition if the fix affects airflow, access, life safety, pressure class, rated assemblies, equipment, or another trade.

CBring the foreman/detailer the location, what you checked, and what decision you need before cover, startup, or rework.

Do not do this

Do not assume a clean-looking condensate line will drain under fan pressure if the trap/vent logic is wrong.

Why this matters

Bad condensate trapping causes ceiling damage, equipment cabinet flooding, mold risk, and startup callbacks.

Final verification

Use this as field training guidance. Final direction still comes from the foreman, approved drawings, project specs, manufacturer installation instructions, employer safety policy, and AHJ/code requirements.

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