What You'll Learn

• How to select the correct TrueFlow Grid size for your return grille
• How to place the grid for an airtight seal and accurate measurement
• How to connect the TrueFlow Grid to the TEC DG-1000 (or DG-8)
• How the App-to-App connection works between the TEC TrueFlow App and measureQuick
• How to read and confirm airflow results in measureQuick
• Why measured airflow produces better diagnostics than estimated airflow
• How to troubleshoot common setup problems

What You'll Need

• Device: iPhone (iOS 15+) or Android phone (Android 10+) with measureQuick installed
• Account: measureQuick account with active subscription (see Creating Your measureQuick Account)
• TrueFlow Grid: TEC TrueFlow Grid in the correct size for your return grille
• Pressure gauge: TEC DG-1000 or DG-8 digital pressure gauge
• TEC TrueFlow App: Installed on the same phone as measureQuick
• Time: 15-20 minutes for first setup; 5-10 minutes once familiar

Step-by-Step Guide

Step 1: Select the Right Grid Size

The TrueFlow Grid must cover the entire return grille opening. Measure the width and height of the opening (not the grille frame) and match it to one of the available sizes.

The TrueFlow Grid has 8 adapter plate sizes covering these standard filter openings. If your return grille opening is larger than 25 x 25 inches, a single TrueFlow Grid will not cover it. You will need an alternative airflow measurement method (see TrueFlow Airflow Measurement or Flow Hood Testing).

TrueFlow Grid specifications:

How the grid works: The TrueFlow Grid is a known-opening pressure averaging device. It contains multiple sensing ports across its surface that feed into a single pressure channel on the DG-1000. The DG-1000 reads the average pressure drop across the grid, and the TEC TrueFlow App converts that pressure reading into CFM based on the grid's known resistance characteristics for the selected size. This is the same measurement principle used by blower doors and duct testers.

Tip: Bring a tape measure to the job. Guessing the grille size is the most common source of setup error.

Step 2: Prepare the Return Grille

1. Turn the HVAC system ON. The blower must be running during the airflow measurement.
2. Locate the return grille you will measure.
3. Remove the return air filter from behind the grille. The TrueFlow Grid replaces the filter during the test.
4. If the grille has a hinged door, swing it open so the duct opening is fully exposed.

[Visual Reference] With the return air filter removed, you should see the open duct cavity behind the grille. The rectangular opening is where the TrueFlow Grid will be placed. If the grille has a hinged door, it should be swung fully open so the entire duct cross-section is accessible. Note the filter size printed on the grille frame or the filter itself before removing it.

Tip: Write down or photograph the filter size before removing it. This is a quick way to confirm you have the right grid size.

Step 3: Place the TrueFlow Grid

1. Hold the TrueFlow Grid flat against the return grille opening, on the duct side (behind the grille, not the room side).
2. Press all four edges firmly against the opening. The grid must seal completely. Any air bypassing the grid will produce a low reading.
3. If using the 25 x 25 cut-to-fit model, trim the grid to match the exact opening dimensions before placement.

[Visual Reference] The TrueFlow Grid sits flat against the return grille opening on the duct side (behind the grille, not the room side). All four edges of the grid should press firmly and evenly against the opening with no visible gaps. Any air bypassing the grid around the edges will produce a falsely low airflow reading. Run your hand around the perimeter while the blower runs to check for leaks.

Check the seal by running your hand around the perimeter of the grid while the blower is running. You should not feel air escaping around the edges.

Step 4: Power On and Connect the DG-1000

The TrueFlow Grid does not connect directly to measureQuick. It connects to a TEC DG-1000 (or DG-8) digital pressure gauge, which does the pressure measurement. Here is the connection chain:

TrueFlow Grid --> DG-1000 (via BLE) --> TEC TrueFlow App --> measureQuick

1. Power on the TEC DG-1000.
2. Make sure Bluetooth is enabled on the DG-1000 (check the DG-1000 settings menu).
3. On your phone, open the TEC TrueFlow App (not measureQuick yet).
4. In the TEC TrueFlow App, tap to scan for your DG-1000. Select it from the list of available devices.
5. Wait for the connection indicator to show "Connected."

Airflow measurement equipment: TEC DG-1000 manometer, TrueFlow Grid nozzle plate, and duct tester connection diagram showing how pressure converts to CFM

The DG-1000 measures the pressure drop across the TrueFlow Grid. The TEC TrueFlow App uses this pressure reading, combined with the grid size, to calculate actual CFM.

DG-1000 specs for reference:

• Two independent pressure channels
• Range: -2,500 to +2,500 Pa (-10 to +10 in. H2O)
• Accuracy: 0.9% of reading or 0.12 Pa, whichever is greater
• Resolution: 0.1 Pa (0-999.9 Pa), 1 Pa (1,000+ Pa)
• Connectivity: WiFi, Bluetooth, USB, Ethernet (four options; the TrueFlow App uses Bluetooth)
• Battery: 10+ hours continuous operation (rechargeable lithium-ion)
• Dimensions: 7.0 x 4.2 x 1.4 inches
• Touch screen interface with magnetic mounting
• Auto-zeroing: The DG-1000 automatically re-zeros itself at regular intervals. You will hear a click sound when it auto-zeros. Unlike Fieldpiece manometers, you do not need to manually zero the DG-1000 before each reading.

The TEC DG-8 ($699.00) is also compatible as the companion gauge for TrueFlow Grid. It has one pressure channel, Bluetooth + USB connectivity, and the same 0.9% accuracy.

Step 5: Configure the TEC TrueFlow App

1. In the TEC TrueFlow App, select your grid size from the dropdown menu. This must match the grid you placed on the return grille.
2. Confirm the system fan is running.
3. Tap Start Test (or equivalent) in the TEC TrueFlow App.
4. The app reads the pressure differential from the DG-1000 and calculates CFM.
5. Wait for the reading to stabilize. This typically takes 5-10 seconds. A stable reading means the CFM value stops fluctuating.

[Visual Reference] The TEC TrueFlow App shows the selected grid size in a dropdown at the top, a large CFM reading in the center of the screen, and a stability indicator. When the reading stabilizes (CFM value stops fluctuating), the measurement is ready to send to measureQuick. The app calculates CFM from the pressure differential measured by the connected DG-1000.

The TEC TrueFlow App now holds the measured airflow value. The next step sends it to measureQuick.

Step 6: Send Airflow Data to measureQuick (App-to-App)

This is the key step that distinguishes the TrueFlow Grid from direct Bluetooth tools. The TrueFlow Grid uses an App-to-App connection. The TEC TrueFlow App shares data with measureQuick; the grid does not pair directly with measureQuick via Bluetooth.

1. Open measureQuick on the same phone.
2. Start or resume the project and test workflow where you need the airflow reading.
3. Navigate to the airflow measurement field in your active workflow.
4. measureQuick detects the TEC TrueFlow App running on the same device and receives the calculated CFM value.
5. The airflow field populates automatically with the measured value.

measureQuick workflow screen showing the airflow field populated with a CFM value from TrueFlow

In the measureQuick database, this measurement is recorded with airflow_source = "trueflow", distinguishing it from estimated or manually entered values.

Tip: Both apps must be running on the same phone. If you run the TEC TrueFlow App on one device and measureQuick on another, the App-to-App transfer will not work.

Step 7: Verify the Reading in measureQuick

After the airflow value appears in measureQuick:

1. Confirm the CFM value looks reasonable for the system. A 2-ton system typically moves 700-900 CFM. A 3-ton system typically moves 1,050-1,350 CFM. The general benchmark is 350-450 CFM per ton.
2. Check that the diagnostics screen reflects the new airflow data. Subsystem evaluations that depend on airflow (superheat, subcooling, temperature differential) will update.
3. Review the Vitals Score. Measured airflow from TrueFlow carries more weight in the Vitals Score than estimated airflow, because the measurement is direct and accurate.

measureQuick diagnostics screen with airflow populated and Vitals Score updated

Step 8: Remove the Grid and Reinstall the Filter

WARNING: REMOVE THE TRUEFLOW GRID AND REPLACE THE FILTER before continuing with the rest of your diagnostic workflow. Leaving the TrueFlow Grid in the unit is the single most common procedural error cited across live training events. The grid blocks normal airflow, which means all subsequent measurements - temperatures, pressures, superheat, subcooling - will be wrong. Every reading you take with the grid still in place is unreliable.

After you record the measurement:

1. Remove the TrueFlow Grid from the return grille.
2. Reinstall the return air filter.
3. Close the grille if applicable.
4. Confirm the filter is back in place before moving to any other measurement step.

Do not leave the TrueFlow Grid in place during normal system operation. It is a measurement tool, not a filter.

Why Measured Airflow Matters

measureQuick can estimate airflow from system parameters when no direct measurement is available. Estimated airflow is calculated from equipment ratings and operating conditions. It is useful as a fallback, but it assumes the duct system is performing as designed.

Measured airflow from the TrueFlow Grid reflects what the system is actually delivering. As Jim Bergmann noted on the Enthalpy Method podcast, "instruments are very expensive, right, so that TrueFlow grid, that's like seven hundred dollars" - but the diagnostic accuracy it provides pays for itself by catching duct problems that estimated airflow masks. This matters because:

• Duct restrictions, leaks, and dirty filters reduce actual airflow below design values.
• Superheat and subcooling calculations are more accurate with real CFM data.
• The Vitals Score weights measured airflow higher than estimated airflow.
• Static pressure readings combined with measured airflow reveal duct system problems that estimated airflow masks.

In the V12 database, tests with airflow_source = "trueflow" produce the most reliable diagnostic outputs. Tests with airflow_source = "estimated" or "manual" are useful but carry wider uncertainty.

Video Walkthrough

• (10:47) - The primary TrueFlow Grid integration video. Chris Hughes walks through the complete TrueFlow-to-measureQuick data flow including grid setup, DG-1000 connection, and App-to-App transfer

• (66,533 views, 72 min) - Full diagnostic walkthrough that includes airflow measurement in the context of system commissioning

• (6,296 views, 7:04) - Demonstrates how measured airflow data helps identify duct leakage by comparing measured CFM against expected values

• (23,171 views, 1:05:15, HVAC School) - Jim Bergmann discusses airflow measurement methods including the TrueFlow Grid in context of static pressure and capacity testing

Tips & Common Issues

Air leaking around the grid edges

The most common cause of low CFM readings. Run your hand around the grid perimeter while the blower runs. If you feel air escaping, reposition the grid and press it firmly against all four edges. On rough or uneven duct openings, use painter's tape or foam weatherstrip around the perimeter to create a better seal.

Wrong grid size selected in the TEC app

The TEC TrueFlow App uses the grid size to convert pressure into CFM. If you select the wrong size in the app, the CFM calculation will be incorrect even if the physical setup is perfect. Double-check that the size in the TEC app matches the actual grid you placed.

Filter left in place behind the grid

The TrueFlow Grid replaces the filter during the test. If the filter is still installed, the grid sits on top of it and the pressure reading reflects the combined restriction of both the filter and the grid, producing an inaccurate measurement. Always remove the filter before placing the grid.

DG-1000 not connecting to TEC TrueFlow App

Confirm Bluetooth is enabled on both the DG-1000 and your phone. Make sure the DG-1000 is powered on and not already connected to a different device. If the DG-1000 has been paired with another phone, you may need to clear its Bluetooth pairing list in the DG-1000 settings. The DG-1000 also supports WiFi, USB, and Ethernet, but the TrueFlow App specifically uses Bluetooth.

Airflow value not appearing in measureQuick

Both apps must be running on the same phone. If you switch phones between the TEC TrueFlow App and measureQuick, App-to-App data transfer will not work. Also confirm that you have an active test workflow open in measureQuick before switching from the TEC app.

CFM reading seems too low

Check for air leaks around the grid first. Then verify the blower is running at the correct speed (not a reduced fan speed setting). If the system has multiple return grilles, you are measuring only one of them. Total system airflow is the sum of all return grille measurements.

CFM reading fluctuates and will not stabilize

Wait at least 5-10 seconds after placing the grid before recording. The 5-second stabilization window is a standard practice for pressure averaging with the TrueFlow Grid. If the reading continues to fluctuate, check for doors opening/closing in the conditioned space, other return grilles that may be partially blocked, or wind effects on exterior ductwork. Close interior doors near the return to reduce pressure fluctuation.

Non-standard opening sizes

If your return grille opening does not match a standard grid size, use the 25x25 cut-to-fit grid. For openings that are slightly larger than the grid, use blue painter's tape, cardboard, or foam weatherstrip to seal the gap between the grid edge and the duct opening. Keep some sealing material in your TrueFlow bag for these situations. The grid must cover the opening completely; any air bypassing the grid produces a low reading.

Angled filter slots

Some systems have angled filter slots where the filter sits at a diagonal. The TrueFlow Grid does not measure accurately in angled orientations because airflow distribution across the grid surface becomes uneven, with a dead spot on one side and concentrated flow on the other. For angled filter slots, place the grid at the bottom of the slot where it can sit flat, or use an alternative measurement point.

Variable speed motor behavior during testing

On systems with variable speed (ECM) blower motors, the motor may ramp up when it senses the added restriction of the TrueFlow Grid. Run the system in high speed/high stage during TrueFlow measurements. If the system is in a lower stage or auto mode, the motor may compensate and produce readings that do not reflect normal operating airflow. PSC motors do not adjust speed in response to restriction, so this concern applies primarily to ECM and constant torque motors.

TrueFlow Grid battery

The TrueFlow Grid has a 2,000 mAh lithium-ion polymer rechargeable battery (USB-C charging). Charge it before heading to the job. A low battery can cause intermittent Bluetooth disconnections with the DG-1000.

Related Articles

Prerequisites (complete these first):

• Bluetooth Pairing Basics
• Static Pressure Measurement

Follow-up articles (next steps after this one):

• TrueFlow Airflow Measurement (advanced techniques, ductless systems, register readings)
• Flow Hood Testing
• Interpreting Static Pressure Results

Related in the same domain:

• Smart Tool Overview
• Bluetooth Pairing Basics
• Fieldpiece Probe Pairing
• Bluetooth Troubleshooting

Need Help?

If you get stuck or this article does not answer your question:

• Check the Related Articles section above
• Contact measureQuick support: support@measurequick.com