Step-by-Step Setup for the Retrotec US340 Duct Tester with DM32

Ever wondered what’s involved in a duct leakage test?

It’s more than just hooking up a fan and pressing a button. From sealing every register to fine-tuning pressure readings, every step impacts your results. Below, we break down the setup process for the Retrotec US340 Duct Tester with DM32, so you know exactly what it takes to get an accurate test.

This isn’t an exhaustive guide—every house has its quirks—but whether you’re a pro looking to refine your process or just curious about what’s happening behind the scenes, this will give you a solid idea of what’s involved.

Vent Cap SystemsRetrotec, Ltd.Retrotec US340x DUCTESTER (Latest Model)In this close-up shot, the DM32x manometer takes the spotlight, revealing its sleek design and intricate details. Attached to the fan, which is seamlessly connected to a return air vent, the image emphasizes the integrated nature of the system. It's a visual testament to Retrotec's commitment to precision and user-friendly design, inviting potential users to appreciate the tool's finesse and practicality.

Retrotec US340x - Product Page

1. Pre-Test Preparation

Gather Equipment:

Inspect the System:

  • Identify all supply and return vents.
  • Locate air handler(s) and ductwork.
  • Ensure all dampers are fully open.

Seal the System:

  • Close all exterior doors, windows, and vents.
  • Seal all supply and return registers using Vent Caps or duct mask tape.
  • Seal any leaks outside the conditioned space, such as gaps in the return plenum.

Turn Off HVAC Fans:

Shut down all thermostats to prevent system operation during testing.

2. Setting Up the Duct Tester

Connect the Fan:

  • Attach the flex duct to the US340 duct tester fan.
  • Secure the duct to the return side of the system using the included flange and collar.

Setup the DM32 Gauge:

  • Power on the DM32 and select "Duct Testing" mode.
  • Connect the pressure hoses:
    • Blue hose: Connect to the reference port on the fan (measuring duct pressure).
    • Red hose: Connect to the duct tester to measure fan pressure.
    • Yellow hose (if needed): Can be used for an additional pressure reference point.

Range Plate Selection:

  • Insert the correct range plate based on the expected leakage.
  • Larger leaks → smaller plates to maintain proper pressure differential.
  • Smaller leaks → larger plates for accurate readings.

3. Conducting the Test

Set the Baseline Pressure:

  • With the duct tester fan off, check the baseline pressure.
  • Adjust for any baseline offset using the gauge.

Pressurize or Depressurize:

  • Pressurization Test: Set the fan to blow air into the system.
  • Depressurization Test: Set the fan to pull air from the system.
  • Adjust the fan speed to reach 25 Pascals (Pa) of pressure difference.

Record the Readings:

  • DM32 will display the flow rate required to maintain 25 Pa.
  • Note the CFM @ 25 Pa (Cubic Feet per Minute at 25 Pascals).

Adjust for Multi-Zone Testing:

  • If the home has zoned ductwork:
    • Open one zone at a time and repeat the test.
    • Record each zone’s leakage separately.

4. Interpreting Results

Compare Leakage to Standards:

  • Check against ASHRAE 62.2 or ENERGY STAR requirements.
  • Acceptable leakage typically falls under 4-6 CFM per 100 sq. ft.

5. Completing the Test

By following these steps, you’ll get an accurate measurement of duct leakage and identify efficiency improvements for the row house’s HVAC system. 🚀