Despatch LND Series with Protocol Plus - Manual (Page 23)

15
Automatic Nitrogen and Water Cooling
Your oven may be fitted with optional automatic water cooling and/or nitrogen control
features. These features replace the manual on/off valves with solenoid valves which
can be operated either by switches in the control panel or programmed event outputs on
the temperature control instrument.
The additional switches in the control panel have AUTO and MANUAL positions.
Placing the switch in MANUAL energizes the appropriate solenoid valve. Leaving the
switch in the AUTO position allows the solenoid valve to be operated by the control
event outputs.
Refer to the following section on the control instrument for more information on
programming the event outputs. The standard configuration for these optional features
is for event relay 1 to operate water cooling, event relay 3 to operate nitrogen purge,
and event relay 4 to operate nitrogen maintain. In addition, if the optional door lock
feature is also installed, it will be in the locked position any time the nitrogen maintain
solenoid is energized.
Typically, the control is programmed so that the purge and maintain valves are
energized at the beginning of a program in a segment of long enough duration to purge
the oven (see the oxygen level chart discussed earlier). The next program segment then
de-energizes the purge valve while leaving the maintain valve energized. The maintain
valve should be left energized for as long as the nitrogen level is desired to be
maintained.
The water cooling solenoid valve is energized in the last segment(s) of the program to
bring the chamber temperature down to a safe unloading temperature.