SHOP TALK
troubleshooting
Diagrams and information included in Troubleshooting are supplied from various sources, and
RSES and RSES Journal assume no responsibility for the accuracy of the information presented.
A Gas Furnace
Combustion Analysis
BY JIM JOHNSON
E-mail your real-life troubleshooting problem—along with the
ultimate solution you found—to [email protected]. Be
sure to include as much supporting documentation as possible—
wiring diagrams, model/serial numbers, etc. If your problem is
published, you will be rewarded with a free heat-pump training
video, “Uncomplicating the Heat Pump: Refrigeration and Air
Flow Systems.”
I
n this month’s troubleshooting problem, you have already
found and solved the electrical problem that first brought
you to a home to repair a five-year-old gas furnace that was
not heating. As part of your follow-up process, to make sure
the system is performing properly once the repair is done,
you perform a combustion analysis.
The equipment is an 80% efficiency natural-gas unit,
standard up-flow, forced-air type unit. When you take the
appropriate steps to access the vent stack and employ a device that measures the details of combustion, the print-out
from your instrument shows the information in Figure 1.
Your two-part troubleshooting question is:
Which two factors do you scrutinize the closest in this particular situation, and what action do you need
to take in order to achieve maximum
efficiency for this equipment?
The answer to this month’s problem will be published in the March
2014 issue of RSES Journal.
If you have the answer to this question, submit your
name, home address, a day and evening phone number,
6 RSES Journal JANUARY 2014
Efficiency
Excess Air
Stack Temp
Primary Temp
Delta Temp
Oxygen
Carbon Dioxide
Carbon Monoxide
79.4%
80.0%
440°F
70.3°F
42.0°F
10.0%
6.1%
211 ppm
CO Air Free
393 ppm
Draft-0.03 wc
Figure 1
the month in which the question you are answering was
published and your answer to: Jordan Brandes, Associate
Editor, RSES Journal, 1911 Rohlwing Road, Suite A,
Rolling Meadows, IL 60008-1397; e-mail troubleshooting@
rses.org; or fax to 847-297-5038. Make sure your answer is
submitted by Jan. 31, 2014.
All correct answers will be entered into two drawings. The monthly winner will receive a copy of Johnson’s
video training program, “Evaluating Refrigeration Systems:
Troubleshooting & Identifying Problems,” and the quarterly drawing winner will receive the “Heat Pump Training
Package.”
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TAKE THE CHALLENGE
And the winner is…
The answer to the November 2013 problem, “A Gas
Furnace that Will Not Fire,” is that the ignitor has
failed. Our ohmmeter test showed that it had a higherthan-normal resistance, preventing burner ignition.
The winner of the November 2013 drawing is Brandon
Yeager of Greenwood Lake, NY. The winner should call
520-625-6847 or e-mail Johnson to facilitate shipment of
their prize. Drawing must be claimed by Feb. 28, 2014.
Jim Johnson, Director of Training, Technical Training
Associates, develops technician training workshops, DVDs,
audio books and e-books, many of which are now available at the RSES online store. Two new videos, “A Heat
Pump That Won’t Cool” and “A Heat Pump That’s Not
Delivering Any Air,” are now available for $20 each or
$30 for the pair. 40 minutes in length, the videos provide
information on a specific approach to troubleshooting a particular problem. Also be sure to check out the new website
at www.hvacrtroubleshooting.com, which focuses on equipment servicing and allows technicians and students to post
comments and questions relative to specific troubleshooting situations detailed on the site. For more information,
visit www.techtrainassoc.com, write HC 70, Box 3172,
Sahuarita, AZ 85629 or e-mail [email protected].
w inner
Yeager
9 Brandon
Greenwood Lake, NY
is the winner of the November 2013
Troubleshooting Challenge.
Circle Reader Service No. 68
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JANUARY 2014 RSES Journal 7