October 2013
1
Using the DG-700 and TECLOG3 to Measure Worst Case Fan
Depressurization and Appliance Draft
Buildings with natural draft combustion appliances should be routinely tested to ensure that the
spillage of combustion products into the building is unlikely. Combustion safety testing is critical
because of the potential for severe health effects from spillage susceptible appliances, including
carbon monoxide poisoning. Building depressurization, caused by exhaust fans, dryers,
unbalanced forced air distribution systems, and duct leakage can be a major cause of appliance
spillage. As buildings (or combustion appliance rooms) are made tighter, these problems can be
made worse, although very leaky buildings can also have venting problems related to
depressurization. One way to determine how the combustion appliances respond to changes in
building pressures is to perform a worst case depressurization test, along with an appliance draft
test.
If you have a DG-700 gauge (or a DG-500 or APT data acquisition box) and a laptop computer,
you can easily perform and graphically document these important tests. All you need is a copy of
our TECLOG3 software (available for free at
www.energyconservatory.com
) and a
communication cable (USB or 9-pin serial), or TEC WiFi Link to connect the DG-700 gauge to
your computer. Using TECLOG3 along with your DG-700 gauge you can capture and record the
two best indicators of venting performance, namely the pressure in the Combustion Appliance
Zone (CAZ) and the appliance draft pressure. (Consult Chapter 10 of the Minneapolis Blower
Door Operation Manual for more details on combustion safety testing.)
Getting Started/Example File
Below is a quick summary of what is involved in performing these tests. This summary uses an
example test file recorded on a house with a natural draft water heater (the furnace was sealed
combustion). The DG-700 gauge is located in the CAZ for this test.
1.
Set up your DG-700 gauge to measure both the CAZ pressure and the vent pressure for a
natural draft appliance. Since we want to measure the CAZ pressure with reference to
outside, you will need to connect the
Channel A
Reference tap to the outside using a long
piece of tubing. Leave the
Channel A
Input tap open to the CAZ. Connect the
Channel B
Input tap to a static pressure probe installed in the appliance vent. Leave the
Channel B
Reference tap open to the CAZ.
2.
You will need to create a communication link between the DG-700 gauge and your laptop.
You have two options to create this link.
•
Physically connect the laptop to the DG-700 gauge using a USB or 9 pin
communication cable. This will typically require the laptop to be in the CAZ.
Note:
go to
http://www.energyconservatory.com/support/user-tips#1
for information on
using the DG-700 communication ports.
•
Or, use a TEC WiFi Link to create a wireless communication link between the gauge
and the laptop. This will allow the laptop to be almost anywhere in the house.
Note:
s
ee documentation that came with the WiFi Link.
3.
Start TECLOG3 and open the
Configuration Settings
window (click on
Configuration….Settings).
Enter
1.0
seconds into the
Sample Interval
field (this tells
TECLOG3 to take one second average pressure readings).
