Despatch LND Series with Protocol Plus - Manual (Page 63)

55
Tests
Tests should be performed carefully and regularly. The safety of personnel as well as
the condition of equipment may depend upon the proper operation of any one of the
functions of the temperature control. Test the control every 40 hours. Check that the
heater LED is cycling on and off, indicating that the heater is working. Also check the
high limit function to make sure it is working properly.
To test the high limit:
1.
Go to Manual Mode and enter control setpoint value at least 20°F (11°C) lower
than the current process temperature.
2.
Press the Menu key and lower the high limit setpoint to a value just below the
current process temperature.
3.
The high limit alarm indicator should flash and a high limit alarm message should
be displayed. Verify that the heater relay has been disabled by checking that
2LED on the control panel circuit board is not lit.
4.
Return the control setpoint and high limit setpoint values to their original values.
5.
Press the Reset key.
Nitrogen Supply
Turn the three-way valve on the control panel to the
OFF position and screw the adjusting knob clockwise
on both PURGE and MAINTAIN flowmeter all the way
to the OFF position. Then open the tank valve on the
nitrogen supply and set the pressure regulator to
about 40 PSI. Check the nitrogen plumbing for leaks
with a soapy water solution. As nitrogen gas is odorless, all leaks should be stopped to
prevent the possibility of suffocation in a small work areas. Gas from a nitrogen leak
might displace much of the oxygen in the atmosphere.
WARNING:
Disconnect the main power
switch or power cord before
attempting any repair or ad-
justment.