70
SERVICING
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,
alignment, 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.
WARNING
Disconnect gas and electrical power supply.
1. Connect a water manometer or adequate gauge to
the inlet pressure fitting of the gas valve.
2. Remove the pressure tap fitting at the manifold if
provided or check at the gas valve outlet fitting and
connect another manometer or gauge.
Inlet
Pressure Boss
Low Fire
Regulator Adjust
Manometer
Manometer
Hose
High Fire Regulator
Adjust
Regulator
Vent
Outlet
Pressure Boss
Open to
Atmosphere
Single Stage 36G54
Summary of Contents for DRG0361DL00001S
Page 20: ...20 SYSTEM OPERATION...
