SERVICING
55
S-305 CHECKING MAIN BURNERS
The main burners are used to provide complete combustion
of various fuels in a limited space, and transfer this heat of the
burning process to the heat exchanger.
Proper ignition, combustion, and extinction are primarily due
to burner design, orifice sizing, gas pressure, primary and
secondary air, vent and proper seating of burners.
BECKETT BURNER
WARNING
Disconnect gas and electrical power supply.
In checking main burners, look for signs of rust, oversized and
undersized carry-over ports restricted with foreign material,
etc.
S-306 CHECKING ORIFICES
A predetermined fixed gas orifice is used in all of these
furnaces. That is an orifice which has a fixed bore and
position.
A
GAS
STREAM B
DENT OR
BURR
GAS
STREAM B
The length of Dimension "A" determines the angle of Gas
Stream Defraction, "B".
A dent or burr will cause severe deflection of gas stream.
No resizing should be attempted until all factors are taken into
consideration such as inlet manifold gas pressure, align-
ment, and positioning, specific gravity and BTU content of the
gas being consumed.
The only time resizing is required is when a reduction in firing
rate is required for an increase in altitude.
Orifices should be treated with care in order to prevent
damage. They should be removed and installed with a box-
end wrench in order to prevent distortion. In no instance
should an orifice be peened over and redrilled. This will
change the angle or deflection of the vacuum effect or
entraining of primary air, which will make it difficult to adjust
the flame properly. This same problem can occur if an orifice
spud of a different length is substituted.
WARNING
Disconnect gas and electrical power supply.
1. Check orifice visually for distortion and/or burrs.
2. Check orifice size with orifice sizing drills.
3. If resizing is required, a new orifice of the same physical
size and angle with proper drill size opening should be
installed.
S-307 CHECKING GAS PRESSURE
Gas inlet and manifold pressures should be checked and
adjusted in accordance to the type of fuel being consumed.
