Oriflow Cobra User manual

Cobra
Duct Leakage Tester
User Manual

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Cobra Tester User Manual © Copyright 2021
Links to Online Help
(QR Code)
Video –Duct Leakage Testing
Online Technical Library
Online Max Leakage Calculator
(SMACNA Leakage Class)
Online Max Leakage Calculator
(% Allowable)

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Cobra Tester User Manual © Copyright 2021
Table of Contents
Introduction
Introduction ……………………………………….………………………….…………… 3
Safety Precautions
Safety Precautions ………… READ FIRST! ……….….……………….……………… 3
Prior to Testing
Are You Using the Correct Tester? …………………………………….…...…………. 4
System Preparation …………………….……………….…………….……...….……… 4
Power Requirements …………………………………....…………….……...….……… 4
Extension Cord Requirements ………………………....…………….……...…………. 5
Flex-Duct Length ………………………………………...…………………….……...…. 5
Determining Maximum Allowable Leakage ….………..……………...…….….……… 5
FREE Oriflow duct test summary form (SMACNA or DW/143) ………….….………. 5
Determining Which Orifice Plate to Use ……………....……………..……..…………. 6 - 7
Duct Leakage Test Setup and Procedure
Install Orifice Plate and Upper Tube Section ……………………………..………..…. 8 - 9
Connect Flex-Duct to Orifice Tube ………………........…………….……...….……… 9
Connect Flex-Duct and Static Pressure Tap to Duct System ………….……………. 10 - 11
Duct Leakage Test Setup (SUPPLY) ………………….………….….……..…………. 12
Duct Leakage Test Setup (RETURN/EXHAUST) …………………..……..…………. 13
Zeroing Pressure Gauges ……………………………………………..……..…………. 14
Avoiding Over-Pressurization …………………………..……………...…….…………. 15
Obtaining System Test Pressure ……………………………………...…….…………. 15 - 16
Determining Leakage Rate……………………………………………..….….…………. 16 - 17
Troubleshooting
Can’t obtain system test pressure (DUCT PRESSURE TOO LOW) …………….…. 18
Can’t obtain system test pressure (DUCT PRESSURE TOO HIGH) …….……….… 19
ORIFICE PLATE gauge reading maxed out ………......……………...….…....……… 19
GFCI/GFI trips …………………………………………………………………………….. 19
Error Codes ………………………………………………………………………….…….. 19
Zero or very small reading on ORIFICE PLATE gauge .………………........……..…. 20
DUCT SYSTEM Gauge (Digital) Displays UFL or OFL ……………………………….. 21
ORIFICE PLATE Gauge (Digital) Displays UFL or OFL ……………………………….. 21

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Cobra Tester User Manual © Copyright 2021
Introduction
The COBRA duct leakage tester is the most widely used tester in the U.S. It is the simplest to
use tester on the market backed by unparalleled customer service and technical support. Call
us, find out.
The recommended recalibration interval for the plates is 5 years. Note the authority having
jurisdiction may override this requirement, and if so, Oriflow has reasonable rates for re-
calibrating orifice plates manufactured by Oriflow. Call us at 727-400-4881 to receive lead
time and pricing for calibration. After you order the calibration, just ship the two orifice tube
sections along with the Oriflow orifice plates to:
Oriflow Calibrations
2125 Range Rd., Suite B
Clearwater, Florida 33765
Safety Precautions
Before operating your tester, read the following safety precautions:
✓DO NOT operate the tester outdoors, in the rain, or where it will get wet,
✓DO NOT operate the tester while it is near or in water,
✓DO NOT operate the tester with a damaged electrical cord or plug,
✓DO NOT operate the tester without an inlet safety screen,
✓DO NOT put fingers, hands or any object near inlet of blower while it is running,
✓DO NOT touch the blower wheel when the unit is plugged in,
✓DO NOT look into the discharge end of the tester when the unit is plugged in,
✓DO NOT use the tester as a ladder or step stool,
✓DO NOT allow children near the tester,
Things you SHOULD DO:
✓Use an extension cord of the proper gauge (see Table 3 on page 5),
✓Make sure unit is electrically grounded,
✓Use the proper voltage and phase listed on the Voltage/Phase/Hz label (front panel),
✓Lock the casters when the tester is positioned horizontally,
✓Use the tester on level ground,
✓Secure the tester when transporting it,
✓Wear proper hearing protection, safety glasses and work gloves,
✓Seek assistance when lifting the tester (e.g., loading onto truck, going up or down
stairs).

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Cobra Tester User Manual © Copyright 2021
Prior to Testing
Are you Using the Correct Tester?
See Table 1 for the maximum capacity for each duct tester when using the largest orifice
plate.
Table 1 –Duct Leakage Tester Capacities
Model
Maximum Leakage Capacity (cfm)*
System Test Pressure (in.wg.)
0.10
1
2
4
6
7
8
9
10
12
14
16
Cobra
680
cfm
650
cfm
645
cfm
600
cfm
465
cfm
405
cfm
350
cfm
250
cfm
—
—
—
—
Panther
1400
cfm
1350
cfm
1320
cfm
1210
cfm
1065
cfm
970
cfm
875
cfm
875
cfm
615
cfm
270
cfm
—
—
Rhino
1700
cfm
1630
cfm
1550
cfm
1420
cfm
1330
cfm
1255
cfm
1185
cfm
1185
cfm
1035
cfm
895
cfm
660
cfm
480
cfm
* Direct hookup (no flex) and using the largest sized orifice available for the model listed.
System Preparation
Cap off all ends of system using clear plastic and duct tape or sheetmetal duct end caps.
Make sure you test the part of the duct system that leakage testing is required. Usually, this is
from the system fan up to, but not including, the VAV boxes (terminal units). Refer to the
engineer's specifications and all applicable codes and test standards.
Power Requirements
Do you have an adequate power supply for your tester (see Table 2)?
Table 2 –Tester Amp Draw
Tester Model
Voltage
Flow Control
Option
Full Load
Amps
Cobra
115
Slide Gate
12.8
Cobra
115
VFD
14.0
Cobra
230
Slide Gate
6.4
Cobra
230
VFD
8.0

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Cobra Tester User Manual © Copyright 2021
Extension Cord Requirements
If you need an extension cord, is it the proper gauge? See Table 3 below for extension cord
requirements. Note these are minimum requirements. Always error on the side of thicker wire.
Table 3 –Required Extension Cord Wire Gauge
Tester Model
Flow Control
Option
Voltage
Extension Cord
Length (feet)
Minimum
Wire Gauge
Cobra
Slide Gate
115
10 to 50
14
50 to 100
12
Cobra
Slide Gate
230
10 to 50
14
50 to 100
14
Cobra
VFD
115
10 to 50
14
50 to 100
12
Cobra
VFD
230
10 to 50
14
50 to 100
14
Flex-Duct Length
Make sure you have enough flexible-duct with your tester for the job. Each
tester includes 12.5 feet, which is enough for most applications. Extra lengths
of flexible-duct are available at
https://oriflow.com/products/accessories/flexible-duct/.
Determining Maximum Allowable Leakage
To determine the maximum allowable leakage for the project, use ORIFLOW’s
free online programs to make these calculations
(https://oriflow.com/software/).
In the U.S., calculations are done for either of the two typical specifications:
1. SMACNA Leakage Class, or
2. Percentage of system flow.
In Europe, Australia and other countries outside of the U.S., the following DW/143
specification is commonly used:
1. Pressure Classification (Class A, B, C or D)
If the specification uses SMACNA Leakage Class or Pressure Classification, you will need to
calculate the total duct system surface area.
Oriflow has a FREE Adobe test summary sheet that will calculate duct surface area,
leakage factor, allowable leakage, actual leakage and Pass/Fail criteria. You can find
this test summary sheet using the QR code to the right. It’s an excellent tool that can
be printed or emailed.

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Cobra Tester User Manual © Copyright 2021
Determining Which Orifice Plate to Use
After determining the allowable leakage at the system test pressure, refer to the following
tables for the capacities of each orifice plate.
The proper orifice plate is the smallest orifice where the specified allowable leakage falls
between the minimum and maximum leakage at the system test pressure.
For example, if you are testing a system at 4 in.wg. pressure and the maximum allowable
leakage is 350 cfm, you will need a 3-inch orifice plate (See Table 6: 350 cfm falls between
82 and 375).
Table 4 –Tester Capacity using the 1-inch Orifice Plate*
System Test
Pressure
(in.wg.)
Minimum
Leakage**
(cfm)
COBRA Tester
Maximum
Leakage
(cfm)
0.10
9
47
1
9
44
2
9
42
3
9
39
4
9
36
5
9
32
6
9
29
7
9
24
8
9
19
9
9
12
* If you need to measure lower flow rates, contact us about the ‘low-flow’ orifice plate.
** Minimum based on 0.40 in.wg. across orifice plate.
Table 5 –Tester Capacity using the 2-inch Orifice Plate
System Test
Pressure
(in.wg.)
Minimum
Leakage**
(cfm)
COBRA Tester
Maximum
Leakage
(cfm)
0.10
34
180
1
34
170
2
34
165
3
34
155
4
34
140
5
34
125
6
34
115
7
34
95
8
34
75
9
34
45
** Minimum based on 0.40 in.wg. across orifice plate.

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Cobra Tester User Manual © Copyright 2021
Determining Which Orifice Plate to Use (continued)
Table 6 –Tester Capacity using the 3-inch Orifice Plate
System Test
Pressure
(in.wg.)
Minimum
Leakage**
(cfm)
COBRA Tester
Maximum
Leakage
(cfm)
0.10
82
440
1
82
420
2
82
410
3
82
390
4
82
375
5
82
340
6
82
290
7
82
245
8
82
195
9
82
130
** Minimum based on 0.40 in.wg. across orifice plate.
Table 7 –Tester Capacity using the 4-inch Orifice Plate
System Test
Pressure
(in.wg.)
Minimum
Leakage**
(cfm)
COBRA Tester
Maximum
Leakage
(cfm)
0.10
175
680
1
175
650
2
175
645
3
175
630
4
175
600
5
175
545
6
175
465
7
175
405
8
175
350
9
175
250
** Minimum based on 0.40 in.wg. across orifice plate.

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Cobra Tester User Manual © Copyright 2021
Duct Leakage Test Setup and Procedure
Install Orifice Plate and Upper Tube Section
The orifice plate that was determined from the previous section should now be installed with
the serial number facing upwards so the corresponding calibration certificate may be
referenced after installation. Refer to Figures 1 through 4.
Figure 1 –Install Orifice Plate and then Rotate Clockwise
Figure 2 –Rotate Orifice Plate Clockwise until it Locks in Place

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Cobra Tester User Manual © Copyright 2021
Install Orifice Plate and Upper Tube Section (continued)
After the orifice plate is locked in place, place the upper tube section over the bolt/wing nut
set, rotate clockwise, and tighten wing nuts (Figures 3 and 4).
Figure 3 –Install Upper Tube Section and Rotate Clockwise
Figure 4 –Tighten Wing Nuts after Rotation