Retrotec Duc-Tester Field Calibration Check

Use this 5 minute check to verify each new Duc-Tester and operator. Repeat every month or after 20 tests to detect problems early. If readings fall outside the specified range, use the Problem/Solution Checklist to fix the problem. No further calibration of the system is ever required unless the Duc-Tester fails this Check.

# Problem Problem Frequency

Typical error

Details

1. Wrong Range Configuration or Device

Constant -80% to +400%

Setting the Digital Gauge to the wrong Range Config or Device is the most common error. Often occurs just after a change of Range or Device.

2. Tubing Connections incorrect

Sometimes 20% Especially for pressurizing houses and depressurizing ducts, tubes are hooked up incorrectly most of the time.

3. Plugged tubes Seldom 20% to 200%

Wide range of errors but not that common.

4. Leaking tubes Less Seldom 10% to 50%

Wide range of errors but not that common. Usually the pressure source will restore some leaked away air but if excessive, pressure indications will fall.

5. Flex duct leaking

Slow degradation

1% to 25%

Very common but small. Always there to some degree. This procedure will identify a leaking duct so it may be patched with duct tape.

6. gauge channels read differently

Rare 1% to 20%

One of 2 channels reading differently. Uncommon but could be a big error. If both channels have an identical error, the effect on the result is negligible.

7. Gauge won’t zero

Rare 1% to 5%

One of 2 channels reading differently. Uncommon but could be a big error. If both channels have an identical error, the effect on the result is negligible. It is the difference between the channels that causes the errors.

Problems causing inaccurate readings in order of frequency are:

Retrotec Duc-Tester

Field Calibration Checkfor pressurization

Measure the flow rate at 25 Pa.

Tape on the Plate (calibrated for 104 cfm at 25 Pa).

Air flow

Detailed Duc-Tester Pressurization Field Calibration Check Procedure

Tape the Field Calibration Plate to the flex duct flange & attach the red tube.

Attach the flex-duct to the outlet side to pressurize the duct. Install the Mid flow ring.

Connect up as if you were testing a duct. Set to “Flow @ 25 Pa”, time averaging to 8 seconds. Adjust the speed until PrA reads close to 25 Pa. Allow the flex duct to straighten out to its full length.

Wait for 30 seconds after fan speed stabilizes.

Depressurization is the same as Pressurization except the flex-duct is mounted on the Duc-Tester inlet.

Air flow

Gauge Model ____Serial # ________

Fan model Serial # ______

97 to 106 cfm is a Pass

Field Calibration Plate for Duc-Tester, 100 cfm @25 Pa. Part number DU-159

Date of Verification Technician CFM @ 25 Pa result on Range _

P= pressurizeD= depressurize

Comments

Duc-Tester Problem/Solution Checklist

Record results.

If Flow is less than 97cfm and greater than 106 cfm, use the Problem/Solution Checklist.

Note: even though the accuracy is within 3% of measured flow, this is a calibration check to see if something is wrong.

#Problem Solution Details

1 Wrong Range Configuration or Device

DM-2 “Range Config” must be set to Mid,

the Device must be set to “DU200”

Ensure the Mid sized flow ring is mounted.

For the Verification test the Range Configuration must be set on the DM-2 to “Mid” and the Device set to “DU200”. The Mid sized low flow plate must be installed.

Getting one of these 3 settings wrong, is the most common error. Incorrectly setting the Range Configuration will result in a -80% error for setting it one range to low to +400% error for setting it one range too high. Setting the Device incorrectly would give a wide range of errors. All large.

The DM-2 retains its previous settings when turned off. If the range changes or the DM-2 is used on a different Device then these settings must be changed also. Always mark down the range configuration and device used on a test form.

If you always test on the Mid Range Configuration and always use the DU200 fan there is no problem but when you change ranges or use your DM-2 on your blower door, then forgetting to change these settings will be a massively largest source of error.

Mid

2 Tubing Connections incorrect

Ensure all tubes are connected properly. Red tube between Verification Plate (which is substituting for the duct leak) and the Blue port on DM-2. You can use the Red port but the duct pressure will show negative when pressurizing.

Yellow tube between the “Ref B (Fan)”port on Duc-Tester and the yellow port on DM-2.

Water drop

3 Plugged tubes Watch for water in the tubes. One drop of water in any of the tubes will allow readings to be taken but they will be very inaccurate. Avoid letting any of the tubes be dragged through puddles of water and check them if water is dropped onto an tube end or gauge fitting. Tubes can be blown out with dry air or simply twirled around to eject the water by centrifugal force. Water drops in the Duc-Tester body can be blown out. Water in the gauge fittings require careful disassembly and should not be attempted.

Tubes can also be twisted inside the equipment, causing restricted flow or may prevent pressure from being transmitted altogether. Do not attempt to repair this.

4 Leaking tubes Check for leaking tubes. Leaking tubes are less of a problem since the tubes don’t have to be perfectly tight to work properly. But, moderate leaks could degrade readings. Check this by blowing in the tubes and crimping them off with a vice grip or paper clip. Don’t hold onto the tubes since heat will cause the pressure to increase. If the pressure drops more than 25% in a minute, the connections must be checked. Often cutting one eight of an inch of tubing off the end of a doubtful connection will solve the problem. Other times, putting an extremely small amount of silicone grease from a barely greasing finger will suffice to stop the leak. Clamp

5 Flex duct leaking

Check visually with bright light If the reading is above 106 cfm ensure the duct is not leaking. Tape up any holes from the inside if you pressurize ducts mostly.

Smoke may be useful for finding leaks or try shining a light inside and notice where it leaks out in a darkened room. Or hold the duct up to the Sun and notice the light coming in as shown in this picture. This hole could not be seen otherwise. Hole

6 One of 2 channels reading differently

Check one channel against the other. If the gauge is having a problem, normally one channel is OK. Compare the two to detect the problem.

Run the Duc-Tester up to maximum speed on the Mid Range Configuration. Set Time Averaging to 8s. T the flow pressure signal from the Duc-Tester to the Yellow and Red ports of the DM-2. Compare Channel A & B at maximum pressure and 50 Pa.

Differences of more than 2% require exchange or factory calibration.

Now, move the tubes to the Green and Blue ports of the DM-2. Compare Channel A & B at maximum pressure and 50 Pa.

7 Gauge won’t zero

Remove all tubes and see if the gauge will hold zero. Make sure Auto Zero is ON.

The above Solutions will fix most problems. If your Duc-Tester still fails the Verification Test, request an exchange or loaner from your distributor while yours is sent back to the factory.

Retrotec Blower-Door Field Calibration Check ProcedureBlower Doors can be tested in a similar fashion using larger calibration plates like the one shown.

Measure the background leakage. Measure the increased leakage with the hole open. The Blower Door should be able to measure the difference within 15% otherwise something may be wrong. Follow a procedure similar to the one outlined in the Duc-Tester Problem/Solution Checklist

Install your Aluminum frame in a small, tight room with the vents and exhaust fans taped shut. Install this panel in the upper hole. Alternatively, cut a piece of cardboard with a one foot by 3 foot hole in it, centered in above the fan.