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7500 Series Manual
6.5.3 Program 3
Program 3 is used in hazardous gas atmospheres.
Pre-Purge
The purge valve (SV) is energized when enclosure pressure is greater than P1.
If enclosure pressure goes above P4 during purging, the SV will shut off but will energize when below P4.
Oscillation of SV may be noticed.
Setting the pressurization valve on the manifold has to be done after purging, or power to SV will have to
be interrupted to set this pressure. The solenoid valve is energized once enclosure pressure is above P1.
Adjusting the pressurization valve before the solenoid valve is energized allows the enclosure pressure to
be above P1 when purging is completed. Fine adjustment of P1 can be achieved after purging, when the
solenoid valve is off.
Operation Mode
After the purge timer counts down, SV shuts off and K1 is energized.
If enclosure pressure drops below P2, the SV is energized and will stay energized for the value of HYST
(%, leakage compensation). If HYST is set to 0, leakage compensation is turned off.
If enclosure pressure drops below P1, K1 turns off immediately or after the Shutdown delay timer times
out. K1 remains off until the enclosure goes through a successful purging.
If enclosure pressure goes above P4, K1 remains. If K2 is set up as Alarm, K2 will energize
6.5.4 Program 4
Program 4 is used in hazardous gas atmospheres.
Pre-Purge
The purge valve (SV) is immediately energized regardless of enclosure pressure.
If enclosure pressure goes above P4 during purging, the SV shuts off but will energize when below P4.
Oscillation of SV may be noticed.
Setting the pressurization valve on the manifold has to be done after purging, or power to SV will have to
be interrupted to set this pressure. The solenoid valve on the manifold is immediately energized before
this pressure can be set.
The purge timer begins counting down when enclosure pressure is greater than P3, and it has to remain
greater than P3 to purge successfully. If the pressure drops below P3 at any time, or for any length of
time during purging, the purge timer is reset and will not begin counting down until pressure is greater
than P3.
Warning!
If enclosure pressure is below P1 when K1 is used to provide power to the enclosure during operation, K1
will remain energized. An alarm is required and must be located such that an operator will be notified of the
alarm.
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