17
Eclipse ThermJet Design Guide No. 205, 3/5/07
Bypass start gas (optional)
A bypass start gas circuit provides gas flow around zone gas
conrol valves during the trial for ignition period. This should only
be used if excess air (proportional or fixed air control) is being
used on low fire; it should NOT be used with on-ratio low fire
systems. During the trial for ignition period, the solenoid valve
in the bypass line plus the automatic gas shut-off valve (either at
each burner or each zone) are opened. If a flame is established,
the bypass solenoid valve closes at the end of the trial for igni-
tion period. If a flame is not established, then the bypass sole-
noid valve and the automatic gas shut-off valve close.
Figure 3.5:
Bypass start gas circuit schematics
Main gas
shut-off
valve train
NC
Bypass option
Main gas
shut-off
valve train
Bypass option
NC
NC
Bypass option
Main gas
shut-off
valve train
Step 3:
Ignition System
(Continued)
Modulating gas with fixed air control
High/low air & gas control
High/Low gas with fixed air control
