TEC DB-DEP700 User manual
Copyright 2011 The Energy Conservatory (revised 02-11)
Fan Configuration Flow Range (cfm)
For Series B Duct Blaster
Ring 1 800 – 225
Ring 2 300 – 90
Ring 3 125 – 10
Quick Guide DB-DEP700
One-Point 25 Pascal Total Leakage Duct Depressurization Test
(pulling air out of the duct system)
Using the Minneapolis Duct Blaster
and DG-700 Digital Gauge
1. Connect the Duct Blaster fan to the duct system.
a) Choose a location to install the Duct Blaster fan. In single, double or triple returned systems, the largest and closest return to the air
handler is usually the best choice. Note: In multi-return systems (a return in every room), installing at the air handler cabinet is often best.
b) Remove any remote filters from the chosen return and then connect the black square transition piece to the return using temporary tape.
Completely seal the remaining open area of the return with tape.
c) Pull the Duct Blaster fan and flex duct out of the carrying case. Disconnect the flex duct from the fan and insert the white foam flow
conditioner into the round transition piece. Connect the flex duct along with one of the Flow Rings to the inlet side of the fan (i.e. the side
without the metal guard) using the round transition piece and connect trim.
When installing the Flow Ring, sandwich it between the round transition piece
and the fan inlet flange. Use the Flow Ring which you think best matches the
needed fan flow. Connect the open end of the flex duct to the square transition
piece using the velcro strap on the flex duct.
d) Connect the fan speed controller to the fan and plug it into a grounded
power outlet.
e) If your DG-700 gauge and fan speed controller are compatible with Cruise Control, install the fan control cable into the 3.5 mm
communication jacks located on top of the DG-700 and on the side of the speed controller (otherwise skip this step). **
2. Prepare the duct system and house for the Test.
a) Adjust the HVAC system controls so that the air handler does not turn on during the Test.
b) Temporarily seal off all remaining supply and return registers, and combustion or ventilation air inlets which are connected to the duct
system. Use Duct Mask
temporary register sealing material provided with your Duct Blaster, or use painters tape and paper.
c) Turn off any exhaust fans, vented dryers, and room air conditioners.
d) Remove all central filters (i.e. in air handler or return plenum).
e) Open a door or window between the building and outside to prevent changes in building pressure when the Duct Blaster is running.
f) If the Duct Blaster is installed in an attic, garage or crawlspace - open vents or access panels or doors from these spaces to the outside.
3. Connect tubing to the DG-700 Pressure
Gauge.
a) Select a location to measure duct
pressure. The best location for measuring duct
pressure is often in the supply trunkline or
plenum. Drill a small hole (1/4" to 3/8" OD)
into the duct to allow a static pressure probe
to be installed. Install the static pressure
probe with the end of the probe pointing into
the air flow that will be coming from the Duct
Blaster fan. If the duct system is reasonably
airtight (e.g. less than 200 cfm25 of leakage),
duct pressures can be measured at any supply
register by inserting a piece of tubing through
the temporary register seal.
b) Connect tubing to the DG-700 as shown
in the illustration to the right.
** Your DG-700 gauge is compatible with Cruise Control if the CONFIG, CLEAR, START and ENTER keys have additional red
lettering below the main black script. Cruise Control also requires a Duct Blaster speed controller with a 3.5 mm communication jack
installed on the side of the controller box, and a fan control cable.
Optional fan
control cable
(for Cruise Control).
Connect the Red
tubing to the
Chan B Input tap.
The other end of
the Red tubing
should be
connected to the
brass tap in the
middle of the DB
fan housing.
Connect Chan A Ref
tap to inside of
building (if gauge is
located in the
building, leave this
tap open). Be sure
window is open.
Connect a piece of
tubing from the
Chan B Ref tap to
the plastic tap on the
Round Transition
Piece.
Connect the Green (or
Clear) tubing to the
Chan A Input tap. The
other end of the Green
tubing should be
connected to the duct
system (by either
inserting into a sealed
register, or connecting
to the end of the
installed static
pressure probe).
Optional fan
control cable
(for Cruise
Control).
Copyright 2011 The Energy Conservatory (revised 02-11)
4. Conducting the Test.
a) Turn on the gauge by pressing the ON/OFF button.
b) Press the MODE button three times to put the gauge into the PR/ FL @25 Mode. In this Mode, Channel A is used to measure duct
system pressure while Channel B is used to display estimated duct leakage at a test pressure of -25 Pascals. (The leakage estimate shown on
Channel B is determined by mathematically adjusting the actual air flow from the Duct Blaster fan using the real-time Channel A duct
system pressure reading and a Can’t Reach Pressure factor.)
c) Check (and adjust if necessary) the selected test Device (i.e. fan) and Configuration (i.e. Flow Ring) shown in the upper part of the
gauge display to match the fan and Flow Ring being used in the test. For example, the Device icon for the Series B Duct Blaster fan is
DB B, and the Configuration icon for Ring 2 is B2. Press the DEVICE button to change the selected fan. Press the CONFIG button to
change the selected Flow Ring.
d) Turn on the Duct Blaster fan.
If Using Cruise Control:
Turn the Duct Blaster speed controller to the “just on” position (i.e. turn the controller knob all the way down counter-clockwise
and flip the on/off switch to “ON” – the fan will not be turning). Now press the Begin Cruise (Enter) button. The Channel A
display will now show the number 25 (your target Cruise pressure). Press the Start Fan (Start) button. The Duct Blaster fan will
now slowly increase speed until the duct depressurization displayed on Channel A is approximately -25 Pascals.
If Manually Controlling Fan:
Turn on the Duct Blaster fan controller and slowly turn the fan controller knob clockwise. As the fan speed increases, the duct
depressurization displayed on Channel A should also increase. Continue to increase the fan speed until the duct depressurization
shown on Channel A is between -20 and -30 Pascals. Do not waste time adjusting and re-adjusting the fan speed control to
achieve a test pressure of exactly -25 Pascals.
e) Channel B will now display the One-Point 25 Pascal Total Duct Leakage estimate. Record this number. If the leakage estimate is
fluctuating more than desired, try changing the Time Averaging setting on the gauge by pressing the TIME AVG button and choosing the 5
or 10 second or Long-term averaging period. (If “------“ or “LO” appear on Channel B, see #5 below).
f) Turn off the Duct Blaster fan. If you are using Cruise Control, this is done by pressing the Stop Fan (Clear) button.
5. “-----” or “LO” appearing on Channel B
Whenever “-----” or “LO” appears on Channel B in the PR/ FL @ 25 Mode, the DG-700 can not calculate a reliable leakage estimate. The
messages “-----” and “LO” appear on Channel B under the following three conditions:
a) “-----” is continuously displayed when the duct test pressure from Channel A is below a minimum value of 5 Pascals. Estimating duct
leakage results when the test pressure is below this value may result in large errors. If possible, install a larger Flow Ring to generate more
fan flow.
b) “LO” is continuously displayed when there is negligible air flow through the test device.
c) “LO” alternates with a flow reading when the air flow reading through the device is unreliable (i.e. you are trying to measure a flow
outside of the calibrated range of the test device in its current configuration). If possible, you should change the test device configuration to
match the flow rate being measured (e.g. install a smaller Flow Ring).
Note: If you change the Flow Ring on the fan, be sure to change the Configuration setting on the gauge to match the installed Ring.
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