Revision 5
34
August 2021
The safe purge indication (Red to Green flag) occurs at a control cabinet pressure positive
pressure of 1" H
2
O (0.25kPa) above atmospheric pressure. The over-pressure relief valve
opens at a control cabinet pressure of 4" H
2
O (1kPa) above atmospheric pressure. The
normal control cabinet purge flow rate is 1.3 SCFM (2.2m
3
/h), as governed by selected
orifices mounted in the cabinet purge vents.
Purging of the control cabinet is required for hazardous area classification and to mitigate
corrosive element exposure on the system electrical equipment. This adjustment must be
performed with the
Cabinet Cooler Air Valve
closed, as the cabinet cooler adds additional
air flow into the control cabinet. If the cabinet cooler air valve is NOT closed when adjusting
the purge air flow, it is possible that the cabinet internal pressure will be sufficient when the
cooler is on (green flag) but insufficient when the cooler is off (red flag).
Seventeen minutes of normal purge air flow is required before the interior of the
control cabinet may be considered safe. DO NOT apply power to the control
cabinet until the control cabinet has been purged, with a green flag indicated on
the purge control box, for at least 17 minutes.
If a green flag cannot be achieved, this indicates that there is a leak somewhere in the control
cabinet that is preventing the necessary positive pressure from being established inside the
control cabinet. Check the retaining nuts on the cabinet door latches and tighten if necessary.
Also check the rubber sealing strip around the door opening for damage.
3.2.2 Cabinet Cooler Air Valve
A vortex cooler is mounted on the top of the analyzer control cabinet to maintain the control
cabinet interior temperature at or below a given setpoint. The location of the vortex cooler is
shown in Figure 15.
Figure 15: Location of Vortex Cooler
Air flow is automatically switched on to the vortex cooler by a control solenoid when the
temperature inside the control cabinet exceeds a user-configurable set-point (by default,
35°C). Additionally, there is a Cabinet Cooler Air Valve mounted behind the purge control
box on the top of the control cabinet. This block valve is used for coarse flow rate adjustment
to the cabinet cooler and is typically set to fully open or fully closed. Minor throttling of the air
flow to the cabinet cooler is possible by opening this valve only partially. The interior
temperature of the control cabinet is indicated on the analyzer display as
Cabinet
Temperature
. When the cooler solenoid switches on, supplying air to the vortex cooler, the
additional air flow into the control cabinet will cause the over-pressure relief valve to open.
Summary of Contents for 943-TGXeNA
Page 130: ...Revision 5 130 August 2021 Figure 82 Oven Cabinet Door Removed ...
Page 131: ...Revision 5 131 August 2021 Figure 83 Control Cabinet Door Removed ...
Page 132: ...Revision 5 132 August 2021 Figure 84 Power Steam Air Signals Connection Details ...
Page 133: ...Revision 5 133 August 2021 Figure 85 AC Wiring Schematic ...
Page 134: ...Revision 5 134 August 2021 Figure 86 DC Signals and Wiring Diagram ...
Page 135: ...Revision 5 135 August 2021 Figure 87 Flow Diagram ...