Technical Tip:
Testing the Furnace Hotline

What is the Lennox-approved method for testing the heat exchanger of the induced-draft furnace line?

Though AHRI's original "3-Step Heat Exchanger Test Method" has always been successful, when the market turned to induced-draft systems, the three-step method became outdated. The latest approach and the only one approved by Lennox is the 5-Step Method published in the Induced-Draft Heat Inspection Procedure fact sheet.

Here is a brief synopsis of the procedure:

STEP 1: Look for flame disturbances.
STEP 2: Measure carbon monoxide levels in the air stream.
STEP 3: Measure CO levels in flue pipe.
STEP 4: Verify proper installation.
STEP 5: Visually inspect heat exchanger.

Note: This is not the comprehensive test process. Please refer to the written AHRI procedure available from your local Lennox representative or the website.

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