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Common Service
Questions Asked
About The AFG Oil Burner
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Periodically we receive
important questions from service technicians and appliance installers pertaining to the
model AFG oil burner. This article, which is an update of the bulletin originally released
in August 1998, will address the most frequently asked questions. 1. WHAT IS STATIC PRESSURE, AND WHY IS IT IMPORTANT WITH
TODAY’S APPLICATIONS?
Static pressure refers to the amount of compressive or expansive
energy in a fluid or gas. This energy will be present whether the fluid or gas is in
motion or at rest. Static pressure is the means of producing and maintaining flow against
a resistance.
High static pressure burners have been developed to accommodate
the more modern, flow restrictive appliances and to assist with low draft conditions. A
drop in static pressure can cause problems that range from delayed ignition, rumbles, and
pulsation to the inability to adjust the burner for clean operation. In these cases, more
static pressure is required to ensure uniform, dependable combustion performance under
variable conditions.
The air handling components of the AFG enable it to develop
greater static pressure than the conventional model AF burner (FIGURE 1). The fan in a
high static pressure burner starts with enough high pressure to effectively push the
products of combustion through the appliance without interruption. The higher static
pressure also acts like a shock absorber or tightly wound spring during the cycle to
resist and absorb flame pulsations. This is especially needed in most modern appliances,
which are designed with more efficient heat exchanger passages and increased draft loss
for greater heat transfer.
2. HOW DOES THE AFG ACHIEVE
ITS HIGHER LEVEL OF STATIC PRESSURE?
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A vital part of the AFG design is a
stationary piece of black plastic installed inside the burner housing. This device is
known as the "air guide". The air guide’s purpose is to direct the air into
the optimal point of the specially designed tablock blower wheel (FIGURE 2). This allows
it to develop a greater static pressure than the model AF style wheel, yet maintain the
same quantity (cfm) of air flow.
WARNING! Do not operate the AFG burner without the air guide
installed. If the air guide is removed, the burner could be seriously disabled, and the
performance severely affected. Delayed ignition, puffback, and appliance soot up could
result.
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3. WHEN REPLACING THE
MOTOR, WHAT FACTORS SHOULD BE KEPT IN MIND?
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The specified motor for the AFG is either of the closed end type or
has small openings in the end bell at the motor shaft end. The small openings are covered
once the fan wheel is installed onto the motor. The back plate of the wheel is positioned
close to the motor end bell with a gap setting of 0.030" (approximately 1/32")
for maximum efficiency and output (FIGURE 3).
Use of a motor style with openings which are not covered once the fan wheel has
been installed will cause a lack of static pressure at the burner retention head due to
leakage and turbulence.
Use a 0.030" (1/32") thickness feeler gauge to measure the gap between the
motor and the blower wheel. Place the gauge flush to the top of the motor and bottom of
blower wheel as shown in FIGURE 3. The set screw must be centered on the flat of
the motor shaft. Tighten the set screw.
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4. WHAT PURPOSE IS SERVED BY
HAVING GASKETS ON THE TRANSFORMER OR IGNITOR BASEPLATE?
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The housing is sealed on the underside of the ignition unit with
gaskets (use kit part no. 51304) to prevent loss of static pressure caused by air leakage
around the baseplate.
Note: On a job site where you are experiencing mild rumbles at start up, shut down, or
during the running cycle, a missing gasket (FIGURE 4) may be contributing to the condition
and should be included in your investigation. Air leakage from the burner housing will
reduce the valuable static pressure needed at the flame retention head.
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5. WHAT IS THE LOW FIRING RATE
BAFFLE, AND WHEN SHOULD IT BE USED?
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The low firing rate baffle, or LFRB (FIGURE 5), was
designed to control the air flow at the discharge of the blower wheel. The baffle reduces
the volume of air from the blower. This allows the air shutter or band to be set with
larger openings while achieving the same combustion performance readings. When firing low
rates in dusty, lint-laden• areas, the wider air openings that accompany the
installation of the LFRB help to ensure trouble free operation by reducing the possibility
of air inlet blocking.
A secondary function of the LFRB is to regulate the quantity of high velocity air
through the center of the retention head. This improves ignition and flame stability. When
retrofitting burners with the LFRB, refer to the chart on page 4 for basic guidelines.
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MIGHT I NEED THE LOW
FIRING RATE BAFFLE? |
For pretested I packaged burners, refer to
the manufacturer’s information to verify that you have the correct factory-tested
combination specified to achieve the best overall performance. Also, remember that most
modern appliances have multiple firing rates. For example, four rates may be fired with
the same retention head, but only two of the four firing rates may utilize the LFRB. How
do you locate this important information? Consult the OEM installation information,
contact the manufacturer, refer to Beckett’s new updated "OEM Spec Guide For
Wholesalers & Installers" (Beckett no. 6711), or call Beckett Technical
Services at 1-800-OIL-BURN (1-800-645-2876).
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| HEAD |
FIRING RATE
(GPH) |
LFRB |
| F0 |
0.5 |
Yes |
| 0.65 |
Yes |
| 0.75 |
No |
| F3 |
0.75 |
Yes |
| 0.85 |
Yes |
| 0.90 |
No |
| 1.00 |
No |
| F6 |
0.85 |
Yes |
| 0.90 |
Yes |
| 1.00 |
No |
| L1 |
0.75-0.85 |
Yes |
| V1 |
0.75-1.00 |
Yes |
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SERVICE CHECKLIST FOR MAINTAINING
ADEQUATE STATIC PRESSURE
Burners designed for higher static pressure
operation deliver exceptional combustion performance over a wide range of applications and
variable conditions. In order to obtain the maximum benefits from this improved design,
always give careful attention to the following requirements:
1. AIR GUIDE. Make sure the air guide is correctly
installed and free from any damage or debris.
2. BLOWER WHEEL. Thoroughly clean the fan blades during
the scheduled tune up. Verify that the blower wheel is set to the specified gap of
0.030" from the motor end bell surface. Replace only with factory specified blower
wheels that are exactly the same. Do not use non-equivalent parts.
3. MOTOR. Use a motor that has a closed end bell or
minimal ventilation openings on the shaft end. If the motor has ventilation openings, they
must not be visible when the blower wheel is installed.
4. IGNITOR I TRANSFORMER BASEPLATE GASKETS. The
baseplate and wiring compartment barrier gaskets must always be installed and in good
condition. Check for signs of wear or damage, and replace questionable gaskets with
factory original parts.
5. LOW FIRING RATE BAFFLE. The baffle should be used
according to the specifications provided by the appliance or burner manufacturer. It
should be securely positioned and kept clean.
Keep this list in mind when servicing the AFG burner, and you
will be able to maintain its static pressure at the required level. This contributes to
dependable, efficient performance, with fewer service hassles and more customer
satisfaction.
We hope this information answers some of the questions that you
may have had regarding the AFG burner and some of the important features that are a part
of its design. If you have a technical question or would like to recommend a topic for a
future issue of our technical bulletins, please feel free to call us. We value any
suggestions you may have and look forward to hearing from you.
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