Retrotec DucTester 340 User manual

Retrotec
Residential DucTester
Operation Manual
Model 340x & 340 DucTester Systems
rev-2019-08-29

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©Retrotec 2017
Made by Retrotec
1060 East Pole Road
Everson, WA USA 98247
For support:
Call 1 [phone] in USA
[phone] outside USA [email protected] or
Fax [phone]
Manual for:
Models 340x with DM32 and Model 340 with DM32 WiFi

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©Retrotec 2017
Copyright © 2014-2019 Retrotec
All rights reserved.
This document contains materials protected under International and Federal Copyright Laws. No part of
this book may be reproduced or transmitted in any form or by any means, electronic or mechanical,
including photocopying, recording, or by any information storage and retrieval system without express
written permission from Retrotec.
Retrotec makes no warranties with respect to this documentation and disclaims any implied warranties
of merchantability, quality, or fitness for any particular purpose. The information in this document is
subject to change without notice. Retrotec reserves the right to make revisions to this publication
without obligation to notify any person or entity of any such changes.
DucTester, Infiltrometer, FanTestic are Trademarks of Retrotec. Other trademarks or brand names
mentioned herein are trademarks or registered trademarks of their respective owners.
Table of Contents
Important equipment-related safeguards .......................................................................... 8
Important occupant safeguards during testing ................................................................... 8
1. Why measure Duct Leakage?......................................................................10
1.1 Energy loss ........................................................................................................... 10
1.2 Duct sealing saves money ..................................................................................... 10
1.3 Problems from duct leakage: ................................................................................ 10
2. How much duct leakage is acceptable under existing Codes? .....................11
3. Model 300 / 400 System Types:..................................................................14
4. Types of Duct Leakage Tests.......................................................................15
4.1 What is duct leakage to the outdoors?.................................................................. 15
4.2 What is duct leakage to the indoors? .................................................................... 15
5. Model 340 DucTesters................................................................................17
Models include US340 and EU340 with 10 inch Flex Duct ................................................. 17
5.1 The calibrated DucTester fan ................................................................................ 17
5.1.1. Range Configurations............................................................................................ 18
5.1.2. Retrotec calibrated fan: Model 300...................................................................... 19
5.2 Digital Gauge........................................................................................................ 21
5.3 Flex Duct .............................................................................................................. 21
5.4 Additional included duct testing components ....................................................... 22
5.4.1. Grill Mask for sealing registers ............................................................................. 22
5.4.2. Umbilical for connecting fan and DM32 gauge .................................................... 22

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5.4.3. Flange for connecting flex to ductwork at register .............................................. 22
5.4.4. Toolbag keeps all testing components in one place............................................. 22
5.4.5. Tubing Accessory Kit ............................................................................................. 22
5.4.6. Power Cord ........................................................................................................... 23
5.4.7. 9v Power Supply adapter for charging DM32 gauge............................................ 23
5.4.8. Additional parts and accessories for the DucTester............................................. 23
6. Prepare for the Duct Leakage Test..............................................................24
6.1 Unpack, connect the gauge to the DucTester ........................................................ 24
6.2 Charge the gauge.................................................................................................. 24
6.3 Follow the Quick Guide that came with your system............................................. 24
6.4 Seal all supply registers......................................................................................... 26
6.4.1. Before beginning the duct leakage test................................................................ 26
6.5 Make all connections on the gauge and fan........................................................... 27
6.6 Blue Tube location matters when testing leaky ducts............................................ 28
6.7 Connect the Flex Duct to the Duct System............................................................. 29
6.7.1. Connect to the return register.............................................................................. 29
6.7.2. OR Connect to the air handler cabinet ................................................................. 30
6.7.3. OR Connect to a return using a Flow Hood .......................................................... 30
6.8 Install Range Configuration on fan ........................................................................ 32
6.9 Select a test direction then connect flex duct to the DucTester.............................. 32
6.9.1. Blow air into the ducts for depressurization ........................................................ 32
6.9.2. Blow air out of the ducts for pressurization ......................................................... 33
7. Set up the gauge to display Duct Leakage Results.......................................34
7.1 Mode setup for duct testing in the US................................................................... 34
7.2 Mode Setup for various standards around the world............................................. 35
7.3 Setting up and using the DM32 gauge for Duct testing .......................................... 35
8. Conduct the Duct Leakage test ...................................................................37
8.1 Total Duct Leakage ............................................................................................... 37
8.2 Duct Leakage to Outdoors with 2 gauges and 2 fans.............................................. 38
8.2.1. Method #1: Set both duct and house to -25 Pa (or 25 Pa).................................. 38
8.2.2. Method #2: Set duct to house pressure to 0 Pa (using DucTester gauge) .......... 39
8.3 Duct Leakage to Outdoors with 1 gauge and 2 fans ............................................... 41
8.4 Combined Total Duct Leakage and Duct Leakage to Outdoors Method .................. 43

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8.5 If no Results are displayed (--)............................................................................... 44
8.6 Cannot achieve test pressure................................................................................ 45
9. Restore the house to pre-test conditions after testing is complete.............46
10. Create a Duct Leakage Test Report with Potential Energy Savings...........47
10.1 Get the Excel spreadsheet based software to run on your system ......................... 48
10.1.1. Enable Macros (with Office 2007) ........................................................................ 48
10.1.2. Enable Macros (with Office 2010) ........................................................................ 48
10.1.3. Showing/Hiding the Ribbon.................................................................................. 49
10.1.4. Enter test information and results into green cells.............................................. 49
10.2 Choose metric or imperial units for results............................................................ 49
10.2.1. Imperial units ........................................................................................................ 49
10.2.2. Metric units........................................................................................................... 49
10.3 Choose Duct Test type .......................................................................................... 50
10.4 Enter the Target test pressure............................................................................... 50
10.5 Enter date the test was carried out ....................................................................... 50
10.6 Enter specific parameters for the conditions of this test........................................ 50
10.6.1. Conditioned Floor Area......................................................................................... 50
10.6.2. Air Handler Flow ................................................................................................... 51
10.6.3. Baseline pressure.................................................................................................. 51
10.6.4. Enter whether pressurizing or depressurizing (Test direction) ............................ 51
10.7 Enter readings from this test................................................................................. 51
10.7.1. Duct Pressure........................................................................................................ 51
10.7.2. “Enter Flow directly” selection or Range Configuration selection ....................... 52
10.7.3. Convert “Flow/Area” data so it can be entered into spreadsheet....................... 53
10.8 Spreadsheet will calculate Cost of Duct Leakage.................................................... 53
10.8.1. % of Duct Leakage to Outdoors ............................................................................ 54
10.8.2. Annual Cooling Cost.............................................................................................. 54
10.8.3. Annual Heating Cost ............................................................................................. 54
10.8.4. Average Duct Operating Pressure......................................................................... 54
10.8.5. Leakage Split ......................................................................................................... 54
10.8.6. Supply Leakage Penalty ........................................................................................ 54
10.8.7. Return Leakage Penalty ........................................................................................ 55
10.9 Save the Duct Leakage Test Report as a PDF file.................................................... 55

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10.9.1. With Office 2007:.................................................................................................. 55
10.9.2. With Office 2010................................................................................................... 55
11. Find air leaks in the ducts........................................................................56
11.1 Using a smoke puffer............................................................................................ 56
11.2 Using theatrical smoke ......................................................................................... 56
11.3 Using an infrared camera...................................................................................... 56
11.4 Using a wet hand.................................................................................................. 56
11.5 Using a Pressure Pan............................................................................................. 56
12. Measure the Air Handler system flow .....................................................58
12.1 For Code compliance ............................................................................................ 58
12.2 Why measure the Air Handler system flow?.......................................................... 58
12.3 Measure with a DucTester as a powered flow hood on the return......................... 58
12.4 Measure air handler flow using a blower door ...................................................... 59
12.4.1. Supply plenum pressure matching method.......................................................... 59
12.4.2. Set pressure in front of return register to zero method or using your Blower Door
as a powered flow hood ....................................................................................................... 61
12.5 Measure large exhaust and intake flow rates........................................................ 62
12.6 Measure with a DucTester on the air handler cabinet ........................................... 63
12.7 Measure with a gauge and a flow grid................................................................... 63
12.8 Measure using air handler blower curves.............................................................. 63
12.9 Measure using Hole Flow on the gauge................................................................. 64
12.10 Measure with a Blower Door attached to the return or cabinet......................... 64
12.11 Other methods ................................................................................................. 64
13. Estimate HVAC system energy loss from ducts........................................65
13.1 Duct Air Leakage Measurements........................................................................... 65
13.2 Methodology........................................................................................................ 65
14. Field Check the DucTester to find out what is not working......................69
14.1 Field Check the gauge ........................................................................................... 69
14.2 Field Check the DucTester as a system .................................................................. 69
15. Avoid common mistakes .........................................................................70
16. Create a Blower Door with a DucTester fan.............................................72
16.1 Use a DucTester to test tight enclosures................................................................ 72
16.2 Blower Door systems for testing tight enclosures.................................................. 72

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Appendix A: Calculate Air Flow based on Channel B Fan Pressure readings......74
Appendix B: Flow Conversion Tables................................................................75
Flow Conversion Table for Duct Test Pressure of 25 Pa..................................................... 75
Appendix C: Calculate flow if required test pressure cannot be reached ..........76
Extrapolation Error for Flow if gauge “n” doesn’t match actual n...................................... 77
Cannot Reach 25 Pa Factors ............................................................................................. 78
Cannot Reach 50 Pa Factors ............................................................................................. 79
Appendix D: Troubleshooting...........................................................................81
“--” appears on display: ................................................................................................... 81
Gauge “Flow” reading does not change? Turn off [@] ...................................................... 81
Fan does not run.............................................................................................................. 81
Checking the DucTester flows .......................................................................................... 81
Adjusting the fan Inlet Nozzle if is rubbing or debris needs to be removed from fan ......... 82
Appendix E: Using a generator for power.........................................................83
Generators ...................................................................................................................... 84
Honda Generator EU3000 (120V, 2000W, 67 lbs).............................................................. 84
GENYX G3000HI (230V, 3000W) generator ....................................................................... 84
Portable Power Supplies.................................................................................................. 84
Black and Decker Electromate 400 Model VEC026BD........................................................ 84
Appendix F: Duct-Test Recording Forms...........................................................85
Total Duct Leakage Test Form Test date: _______________/20____ ..................... 85
Total Duct Leakage Test Form (CA) Test date: _______________/20____.............. 86
Glossary............................................................................................................88

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©Retrotec 2017
Please read and save these instructions before using your
DucTester:
Important equipment-related safeguards
When using electrical appliances, basic safety precautions should always be followed. If Retrotec
equipment is used in a manner that does not follow the information provided in this manual, safety to
the operator and equipment performance may be impaired.
•Avoid contact with moving parts.
•Special attention should be made to keep children and pets away from the fan when it is
operating.
•Do not insert anything into the fan casing while the fan is moving.
•Ensure that no debris is inside the fan casing before operating the fan.
•Keep hands, hair and clothing away from fan at all times.
•The fan can cause damage or injury if it were to fall on someone/something.
•Do not use equipment for other than its intended use.
•Do not stand on the fan, or use the fan to support the weight of another object.
•To protect against risk of electric shock, do not place this equipment or power cord in water or
other liquid.
•Press the power plug firmly into the power receptacle on the fan. Failure to do so can cause
over-heating of the power cord and damage the fan.
•Do not use ungrounded outlets or adapter plugs. Never remove or modify the grounding prong.
•Do not operate any device with a damaged electrical cord, or after an equipment malfunction.
•Use only the included power plug to operate the fan.
•Do not run cord under carpeting. Do not cover cord with throw rugs, runners, or similar
coverings. Do not route cord under furniture or appliances. Arrange cord away from traffic area
and where it will not be tripped over.”
•Turn the unit off and unplug from any electrical outlet before moving and when not in use, or
when making any adjustments to the fan motor or electrical components.
•For use under indoor conditions only.
•For use where there is no exposure to water or dusty substances or explosive materials or
flammable materials.
•Ensure proper cooling of the fan motor.
•Equipment is intended for diagnostic testing and to be operated for brief periods under
supervision by a qualified operator. Not to be used in a role as a household appliance for the
purpose of moving air.
•Failure to follow these instructions carefully may result in bodily injury, damage to property
and/or equipment failure. Failing to operate equipment as intended may void warranty and
compliance with CE mark and other listings.
Important occupant safeguards during testing
Please read the following carefully before carrying out tests:
•If dust, pollen, mold spores, chemicals or other undesirable substances can get blown into living
spaces, keep those susceptible to these substances away from the test area, and wear dust
masks.

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•Do not pressurize a duct system with air that is polluted or exposed to any toxic substances. For
example, blowing air from a car-port into a house or duct system while a motor vehicle is
running can quickly fill a house with toxic carbon monoxide.
•If combustion safety problems are found, tenants and building owners should be notified
immediately and steps taken to correct the problem including notifying a professional heating
contractor if basic remedial actions are not available.
•Air sealing duct work may change the pressure balance in a house and cause back drafting
where it did not occur before. For example, a return leaking to outdoors may have pressurized a
house but when corrected, leaky supplies may reverse that and cause depressurization which
could result in back drafting hot water heaters, furnaces or fireplaces.
•Be aware of all possible sources of combustion. Ensure any appliances do not turn on during the
test. Turn off power to the appliance, or set the appliance to the "Pilot" setting. It is possible
for flames to be sucked out of a combustion air inlet (flame rollout) during a test, which is a fire
hazard and can result in high carbon monoxide levels.
•If combustion safety problems are found, tenants and building owners should be notified
immediately and steps taken to correct the problem (including notifying a professional heating
contractor if basic remedial actions are not available). Remember, the presence of elevated
levels of carbon monoxide in ambient building air or in combustion products is a potentially life
threatening situation. Air sealing work should not be undertaken until existing combustion
safety problems are resolved, or unless air sealing is itself being used as a remedial action.

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1. Why measure Duct Leakage?
1.1 Energy loss
Leaky ducts pose health, safety and comfort problems and account for about 25% of the total energy
lost in a typical house. Because it’s “by far the most cost effective way to save energy” (EPA quote),
building codes now demand higher performance. Although visual duct inspections may be allowed in
some states, duct testing provides an easier, faster, verifiable pass /fail test result. In many instances, it
has a greater impact on energy use than air leaks anywhere else in the house or building enclosure. The
single largest cause of performance problems in small commercial buildings is often duct leakage.
The Duct Leakage Test Report software (in Excel) available from Retrotec can be used to estimate the
energy loss from duct leakage, as described in section 10.8.
1.2 Duct sealing saves money
A study completed in Florida examined 46 homes. They found that sealing the duct leakage reduced air
conditioner use by an average of 17%. This lead to savings of $110 per year, and the repairs were a
onetime cost of $200. Repeatedly, studies show that sealing leaky duct systems is one of the most cost-
effective measures that a home owner can take. Heating or cooling, the same holds true in all climates.
Another study in Arkansas noticed an average savings of 22% on heating bills when duct leakage sealing
was performed.
1.3 Problems from duct leakage:
•Leaky return ducts pull unconditioned air into the duct system, and reduce the efficiency and
capacity of the HVAC system.
•Conditioned (and expensive) air is lost directly to the outside, a crawlspace, or an attic.
•If moist air is pulled into return leaks, the dehumidification system is overwhelmed and the
building will be uncomfortable.
•An inefficient duct system will result in people seeking alternative sources of heating or cooling,
including increased use of electric heaters and fans.
•Dangerous gases, mold spores, insulations fibers, dust, and other contaminants can be drawn
into the duct system and are blown into conditioned spaces.

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2. How much duct leakage is acceptable under existing
Codes?
How much duct leakage is acceptable? The table primarily shows standards for new buildings; only
California has a listing for existing buildings. Changes occur as states adopt the new codes. Check at the
Online Code Environment and Advocacy Network website for up to date details on energy code
adoption. ENERGY STAR programs are listed even though they are voluntary programs rather than
Codes.
Table 1: Duct Leakage Compliance Values (Residential) according to existing Codes
Program/Region
Units/Test
Pressure
Leakage requirement
Abu Dhabi
Building Code
CFM25/100 sq ft at
+ 25 Pa
Total Duct Leakage: <=12 CFM25/100 sq ft
Duct Leakage to Outdoors: <=8 CFM25/100 sq ft
CA: USA
Title 24 –new building
(residential)
CFM25 at
+ 25 Pa
Total Duct Leakage: <=6% of system air handler flow (actual measured airflow
or airflow can be calculated by using the maximum of 400 CFM25 per Ton and
21.7 CFM25 per 1000 BTUh).
Maximum nominal duct leakage is 24CFM25/Ton or 1.302 CFM25/1000 BTUh for
design purposes.
CA: USA
Title 24–new building
(residential)
CFM25 at
+ 25 Pa
If testing at Rough-in without AHU
Total Duct Leakage: <= 4% of system air handler flow (actual measured airflow
or airflow can be calculated by using the maximum of 400 CFM25 per Ton and
21.7 CFM25 per 1000 BTUh).
CA: USA
Title 24–existing
building (residential)
CFM25 at
+ 25 Pa
Total Duct Leakage: <= 15% of system air handler flow (use actual measured
airflow or airflow can be calculated by using the maximum of 400 CFM25 per Ton
and 21.7 CFM25 per 1000 BTUh).
OR
Duct Leakage to Outdoors <= 10% of system air handler flow (use actual
measured airflow or airflow can be calculated by using the maximum of 400
CFM25 per Ton and 21.7 CFM25 per 1000 BTUh).
OR
if fail both, show a 60% reduction in leakage
CA: USA
Title 24–Ducts in
conditioned space
(residential)
CFM25 at
+ 25 Pa
If Ducts are in conditioned space
Duct Leakage to Outdoors: <= 25 CFM25
ENERGY STAR Homes
USA
Version 3 (Rev 05)
CFM25/100 sq ft at
+ or - 25 Pa
Total Duct Leakage: <= 8.0 CFM25/100 sq ft of conditioned floor area
AND
Duct Leakage to Outdoors: <= 4.0 CFM25/100 sq ft of conditioned floor area.
Florida State Energy
Code
FL: USA
2009 IECC International
Energy Conservation
Code
Global
CFM25/100 sq ft at
+ or - 25 Pa
Post Construction Test:
Total Duct Leakage: <= 12 CFM25/100 sq ft conditioned floor area.
OR
Duct Leakage to Outdoors: <= 8 CFM25/100 sq ft conditioned floor area.
OR
Rough-in Test with air handler
Total Duct Leakage: <= 6 CFM25/100 sq ft
OR
Rough-in Test with no air handler:
Total Duct Leakage: <= 4 CFM25/100 sq ft
Required:
-Where ducts are located outside the conditioned space
-In existing houses where more than 50% of the ducts are replaced
Not Required:
- If all ducts are located in the conditioned space

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Program/Region
Units/Test
Pressure
Leakage requirement
2012 IECC International
Energy Conservation
Code
Global
CFM25/100 sq ft at
+ or - 25 Pa
Post Construction Test:
Total Duct Leakage: <= 4 CFM25/100 sq ft conditioned floor area.
OR
Rough-in Test with air handler
Total Duct Leakage: <= 4 CFM25/100 sq ft
OR
Rough-in Test with no air handler:
Total Duct Leakage: <= 3 CFM25/100 sq ft
Required:
-Where ducts are located outside the conditioned space
-In existing houses where more than 50% of the ducts are replaced
Not Required:
- If all ducts are located in the conditioned space
New York State Energy
Code
NY: USA
CFM25/100 sq ft
Total leakage at
±25 Pa
Total Duct Leakage: <= 8.0 CFM25/100 sq ft of conditioned floor area or 6% of air
handler flow. Measured at supply closest to air handler.
Test equipment must be certified by manufacturer that it complies with ASTM
E1554-07 and ASHRAE Standard 152. Duct leakage to outdoors acceptable
under Method A of ASMT E1554-07.
North Carolina Energy
Conservation Code
NC: USA
CFM25/100 sq ft
Total leakage at
–25 Pa
Total Duct Leakage: <= 6.0 CFM25/100 sq ft of conditioned floor area.
Depressurize to -25 Pa measured at supply closest to air handler.
Test equipment must be certified by manufacturer that it complies with ASTM
E1554-07.
Northwest ENERGY STAR
Homes
ID, MO, OR, WA: USA
CFM50/sq ft
CFM50
+ 50 Pa
Total Duct Leakage, air handler in un-conditioned space
CFM50 <= floor area (sq ft) X 0.04 (which is same as CFM50/ sq ft <= 0.04)
OR CFM50 <= 50 (when house < 1250 sq ft)
OR
Total Duct Leakage, air handler in conditioned space
CFM50 <= floor area (sq ft) X 0.06 (which is same as CFM50/ sq ft <= 0.06)
OR CFM50 = 75 (when house < 1250 sq ft)
Not Required:
If both the ducts and air handler are located within the conditioned space
Oregon State Energy
Code
OR: USA
Washington State Energy
Code
WA: USA
CFM25/sq ft
Total leakage at
+ 25 Pa
Total Duct Leakage
with air handler NOT installed <= floor area (sq ft) X 0.04 CFM25
with air handler installed <= floor area (sq ft) X 0.08 CFM25
OR
Duct Leakage to Outdoors (recommended where possible)
<= floor area (sq ft) X 0.06 CFM25

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Table 2: Maximum allowable duct leakage (Residential) according to existing Codes
Code:
Based on
2009
IECC
GA
State
Code
WA
State
Code
VT
Residential
Building
Energy Std
ENERGY
STAR
Homes V3
Rev5
Northwest
ENERGY
STAR Homes
CA Title-
24
Code –
Altered
ducts
CA
Title-24
Code –
New
ducts
Based
on
2012
IECC
Region:
AL CT DC DE FL
IA ID IN KY MA
MI MT NC NE
NH NJ NM NV
NY OH OR RI
SC VA
GA
WA
VT
USA
ID
OR
MO
WA
CA
CA
MD
Test Pressure
± 25 Pa
±
25 Pa
+
25 Pa
±
25 Pa
±
25 Pa
+
50 Pa
+
25 Pa
+
25 Pa
±
25 Pa
Units
CFM
/100 sq ft
CFM
/100 sq
ft
CFM
/ sq ft
CFM
/100 sq ft
CFM
/100 sq ft
CFM
/ sq ft
CFM
CFM
CFM
/100 sq ft
Max Total Duct
Leakage, at rough
in, NO air handler
4
N/A
0.04
4
N/A
N/A
N/A
4% of
system
airflow
3
Max Total Duct
Leakage, at rough
in, with air
handler
6
6
0.08
3
N/A
N/A
N/A
6% of
system
airflow
4
Max Total Duct
Leakage, post
construction with
air handler
12
12
0.08
N/A
8
0.06 CFM/ sq
ft
or 75 CFM
15% of
system
airflow
6% of
system
airflow
4
Max Duct Leakage
to Outdoors, post
construction with
air handler
8
8
0.06
6
4
N/A
10% of
system
airflow
N/A
N/A
The table is listed from left to right in order of loosest to tightest “Total Duct Leakage” requirements.
Disclaimer: This information is not guaranteed. As Codes are being updated continually, this
table represents the most up to date information available at the time of publishing. Please
refer to “rev” date on cover page of this document to determine date of publishing.
Tighter ducts required

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3. Model 340 / 400 System Types:
The Model 340 shares its body and inlet nozzles and Flow Plates with several other models as shown
below. Each one is specialized for a certain application. The Model 340 is used primarily in the US for
relatively leaky US made ducts. The Model 350 is for tighter European ducts that often have to be 100
times tighter than US ducts. The Model 300 is simply the same fan but attached to a door panel for
testing tight houses, apartment, rooms or enclosures. The Model 450 is meant exclusively for testing
commercial ducts at 10 to 100 times the test pressure used for US residential duct that are tested at 25
Pa normally and sometimes 50 Pa. the Model 451 has 10 times the power and is much heavier than the
340 but still a fraction of the old fashioned Commercial duct testers in common use.
This manual focuses on the Model 340x. Be sure to refer to the Quick Guide that came with your
system or can be obtained at: http://retrotec.com
340x
350x
300x
440x/450x
The US DucTester system is
powerful enough to test
leaky ducts found in old
homes and tight ducts in
new homes.
‘European DucTester’
tailored for airtight
European ducts. Just
add the aluminum
frame to test houses.
The Model 300 is ideal
for testing tight houses
as large as a 1600
square feet of floor area
that leak as much as 3
Air changes per Hour.
Commercial duct
testing up to 20 in WC
(5000 Pa) in a
compact package.

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4. Types of Duct Leakage Tests
Air leakage from a duct system can be very hard to identify. Most duct systems are predominantly
behind walls, in attics, crawlspaces, or other unconditioned and hard to access areas. Consequently,
most duct leaks are hard to find, and tend to go unnoticed by owners and contractors alike.
Unfortunately, the harder a leak is to find, the more crucial it tends to be, as these leaks are often found
in hot, humid, damp, and moldy environments. For more details on methods of finding air leaks in the
ducts, refer to later sections.
There are two types of duct leakage tests: a Total Duct Leakage test, and a Duct Leakage to the Outdoors
test.
Total Duct Leakage test is used to determine the total amount of air leakage from a duct system
(to outdoors and indoors)
•only a DucTester system is needed to create a pressure in the duct system
•See section 8.1 for test procedure
Duct Leakage to Outdoors test is used to determine the air leakage from a duct system to the
outdoors only
•Both a DucTester system and a Blower Door system are needed in to create a pressure
in the duct system and the house
•See section 8.2 for test procedure
4.1 What is duct leakage to the outdoors?
Duct systems can be either within the conditioned space (i.e., entirely enclosed in the building), or
outside of the building envelope (i.e., in crawl spaces and/or attics). When ducts are contained in the
conditioned space, air leaking from ducts will end up inside the home. When the ducts are outside of
the conditioned space, duct air leaks go directly to the outdoors; this causes conditioned supply air to
escape, and allows outdoor air to be sucked in through the return. If duct systems run within building
cavities, leaked air can go to both the outdoors and inside the house.
For Duct Leakage to Outdoors tests, the DucTester fan and Blower Door create the same pressure in the
house and the duct system. This neutralizes the pressure between the house and duct system, which
effectively means that there would be no airflow between the duct and inside the house, resulting in the
DucTester system only measuring duct leakage to the outdoors.
The studies discussed in section 1.2 mostly reference homes with duct systems outside of the
conditioned space. Duct leakage to the outdoors has the most impact on HVAC performance. However,
even when all ductwork is located within the building there can be significant loss to the outdoors.
4.2 What is duct leakage to the indoors?
Less is understood about the impacts of duct leakage to the indoors. One of the major concerns is that
leaky return systems can cause basements to depressurize, which can in turn cause combustion gases
(from the furnace) to spill into the home. This can cause serious health problems for the occupants,
especially if the gas mixture is high in carbon monoxide, an odorless, invisible gas and deadly gas. Along
with this problem, negative pressures can also cause increased moisture in the building, and possibly
allow radon gas to infiltrate as well.

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This is a schematic of a duct leakage test. Registers are sealed, the duct tester fan is connected to a
return and the pressure gauge picks up the pressure in the ducts.
Locate the step by step Quick Guide that came with your equipment or access it at www.retrotec.com.
Figure 1: DucTester setup, including tubing locations and necessary connections.

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5. Model 340 DucTesters
Models include 340x 340 with 10 inch Flex Duct
A complete DucTester includes a calibrated fan, a digital dual-channel Model DM32 digital touch screen
pressure gauge, and a Flex Duct with flange to attach the fan to a register. Systems also include a hard-
sided fan case, an AC adaptor for the gauge, and a roll of Grill Mask. All pressure tubing and Control
Cables are bundled together securely in one easy to use Umbilical cable (included), and the included
tubing accessory kit contains T connectors and tube lengths for other non-typical tasks.
Figure 2: A complete duct testing system.
5.1 The calibrated DucTester fan
Retrotec’s DucTester was specifically designed for testing ducts and tight enclosures. It has more than
three times the power necessary to test the leakiest duct system to current standards. The backward
curved centrifugal impeller is perfect for creating high test pressures. The elliptical nozzle is extremely
stable in both the pressurization and depressurization test directions, where it offers equivalent
accuracy in both directions.
A Flow Conditioner is not needed with Retrotec fans for depressurization testing. Some duct testing
fans require a flow conditioner when depressurizing a duct system, in order to get correct readings. The
Retrotec DucTester does not require a flow conditioner because it uses a flow nozzle, which is
intrinsically stable in either direction because the flow gets compressed as it goes through the nozzle.
All Retrotec models comply with ASTM E1554-07, ANSI/ASHRAE 152, ASTM E779-10, EN 13829, ATTMA
TS-1, CGSB 149.10 and RESNET standards.
The DucTester Fan can be used as part of a Blower Door system for testing tight enclosures, as shown in
section 16. For procedures on how to test an enclosure using a Blower Door system, see Residential
Pressure & Air Leakage Testing Manual and/or the Blower Door Operation Manual from the Retrotec
web site. You can also search on blower door as a tag to find these manual, guides and videos on the
website also.

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5.1.1. Range Configurations
Open
74
47
29
Figure 3: Open Range is for the leakiest ducts and houses while Ranges 74, 47, 29 are for progressively tighter ducts.
All Retrotec calibrated fans have multiple Range Configurations in order to measure a wide range of air
leakage flow rates. Select the correct Range Configuration by running the fan speed up to ensure it is
running at over 50% speed and the gauge is giving a flow result. If not change to a lower range and
repeat.
A calibrated fan measures flow by measuring the pressure developed inside the fan, which is often
called Fan Pressure. As the fan speeds up, a suction pressure develops at the inlet of the fan that causes
air to flow. By measuring this Fan Pressure, airflow is calculated using flow equations that are inside the
Retrotec gauge and FanTestic software.
When the fan slows down, the Fan Pressure can become too small to accurately measure flow. To
increase the Fan Pressure, a restriction plate is placed in front of the fan. The fan, consequently, has to
turn faster to maintain the same room or duct pressure, which creates a larger, more accurate Fan
Pressure. By providing a set of flow restricting plates with calibrated holes, Retrotec DucTester fans can
measure flows from 0.005CFM to 800 CFM.
The Model 300 has 4 standard Range Configurations: Open, 74, 47and 29. Open range is accessed by
removing the cover over the fan inlet called End Plate 300. The numbered Ranges are 4 inch Plugs that
snap into the End Plate and will restrict the flow to allow you to measure lower flow rates. The numbers
refer to the approximate hole diameter in millimeters. Most residential ducts in new homes can be
tested using Range 47. Older existing houses can be tested using Range 74 and super tight ducts on
Range 29.
When depressurizing, the Flex Duct must be removed in order to change the Ranges.
Refer to the DM32 Flow Calculator on retrote.com for Range Plug flow capacities.

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5.1.2. Retrotec calibrated fan: Model 300
The Model 300 fan has 0.25 hp backward curved impeller that uses 48 Volts that comes from the
supplied power supply. Any input voltage from 100 to 280 Volts AC, 50 to 60 Hz is acceptable. Speed is
controlled using the knob on the 300 fan or the Retrotec digital gauge, which will control the fan to any
desired Set Pressure or Set Speed.
The Model 300 Fan has a speed control built into the Fan Top with a power input connection, a speed
control knob, an on/off switch, and the Fan Pressure fittings all on one Control Panel. Two CAT-5
connectors are used to connect to any Retrotec gauge for speed control purposes; not to be connected
to the Internet. The second CAT-5 connection allows this fan to be daisy chained to a second fan,
making them receive the same % speed signal thereby making two fans run in unison. The control signal
from one gauge will run both fans.
.
Figure 4: Retrotec Model 300 has a speed control knob and two Ethernet style Speed Control Ports for daisy chaining
speed controls for running many fans together. The yellow and green color coded tubing connections to the gauge are
shown.
The Model 300 has 4 Flow (Fan Pressure) sensors located inside the fan inlet, and 4 self-referencing
pickups located just above and below the fan inlet which are connected to the single green and yellow
ports.
Figure 5: Fan Pressure sensors are located in the fan inlet.
The 4 Flow sensors are located just inside the fan inlet, behind the protective grill. Together, they
measure the Fan Pressure, from which the fan airflow is calculated in the gauge. If the sensors become
blocked, it is possible to clear them by attaching a pressure tube to the yellow Ref B port, and blowing
air through the tube gently.

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The exterior of the inlet has the 4 self-referencing pressure pickups. They are connected to the green
Input B port, and are used as the reference for the Flow (Fan Pressure) Sensors. Self-referencing
ensures that the measured pressure difference is always accurate, no matter what the direction of flow
is with respect to the location of the gauge and operator and whether or not a flex duct is attached to
the inlet of the fan or not.
Figure 6: Self-referencing pressure pickup.