Eclipse ThermJet TJSR Series Design Manual page 8

High/Low/Off Control
The firing rate is set to two positions, the high and low fire
set points, or the burner is shut off. The off state is used
when the low fire rate causes the process temperature to
continue to rise. The setup is the same as high/low
control, but the solenoid is used not only as a flame safety
mechanism, but also for temperature control. When the
system is set to high/low/off control:
1. Manual butterfly valve sets high fire air flow rate.
2. Solenoid valve opens for high fire air flow and closes
for low fire air flow.
High/Low/Off Control
(single burner)
High/Low/Off Control
(multiple burners, shut-off by zone)
High/Low/Off Control
(Multiple burners, shut-off by burner)
8
3. Manual butterfly valve sets low fire bypass air flow.
4. Manual butterfly valve balances the air flow for burner
(multiple burner installations).
5. Ratio regulator adjusts gas flow as loading line
pressure changes due to air pressure changes.
6. Solenoid valve closes if low fire temperature is too
high.
7. Manual butterfly valve sets high fire gas flow.
Main Gas
Shut-Off
Valve Train
Main Gas
Shut-Off
Valve Train
To Other
Zones
To Other
Zones
Main Gas
Shut-Off
Valve Train
To Other
Zones
Figure 3.2 High/Low/Off Control
Eclipse ThermJet Self-Recuperative, V5, Design Guide 208, 9/16/2011
To Other
Zones
To Individual
Burner Piping