7
ThermJet, V2, Technical Information, Edition 2.14
Step 2: Control Methodology
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If the burner is shut off during operation at
temperatures above 1000°F (538°C), provisions
must be made to provide an adequate amount of
flowing combustion air to keep the burner internal
components cool.
The control methodology is the basis for the rest of the
design process. Once it is known what the system will look
like, the components that are in it can be selected. The
control methodology chosen depends on the type of
process to be controlled.
NOTE:
The stated operational characteristics only apply if
the described control circuits are followed. Use of different
control methods will result in unknown operational
performance characteristics. Use the control circuits
contained within this section or contact Eclipse for written,
approved alternatives.
There are two main methods to control the input of a
ThermJet system. Each of these methods also has two
variants. These methods may be applied to single burner
as well as multiple burner systems.
The methods and variants are:
1. Modulating control:
a. Modulating gas & air, on-ratio control or excess air
b. Modulating gas with fixed-air control on page 9.
2. High/low control:
a. High/low air & gas control (pulse firing) on page
b. High/low gas with fixed-air control (Can also be
used for pulse firing) on page 11.
NOTE:
Use of a ratio regulator in a fixed-air system is
optional. However, eliminating the ratio regulator will
adversely affect the ignition reliability at inputs greater
than 40% of maximum.
Use of a ratio regulator in a fixed-air system also provides
automatic gas modulation if system air flow changes over
time (such as a clogged air filter).
In the pages that follow you will find schematics of these
control methods. The symbols in the schematics are
explained in the “Key to System Schematics” (see
Appendix).
Automatic Gas Shut-Off by Burner or
Shut-Off by Zone
The automatic gas shut-off valve can be installed in two
operational modes:
1. Automatic Gas Shut-Off by Burner
If the flame monitoring system detects a failure, the
gas shut-off valves close the gas supply to the burner
that caused the failure.
2. Automatic Gas Shut-Off by Zone
If the flame monitoring system detects a failure, the
gas shut-off valves close the gas supply to all the
burners in the zone that caused the failure.
NOTE:
All ThermJet control schematics on the following
pages reflect a single gas automatic shut-off valve.
This
may be changed to conform to local safety and/or
insurance requirements. (Refer to the ThermJet
Installation Guide No. 205).
NOTICE
