Ametek Thermox 2000 ATEX Series User Manual page 140

6-12 | Thermox Series 2000 WDG-HPII / HPIIC - ATEX
Remote calibration unit (RCU) problem
The RCU contains one normally open solenoid-the aspirator air solenoid.
All other solenoids are normally closed. Problems with the RCU are
usually as follows:
Plumbing leaks
Solenoids not energizing
Plumbing Leak
To check for plumbing leaks, disconnect power from the RCU and pres-
surize the inlets. Apply a leak detecting liquid along the base of the sole-
noids and any plumbing fittings. Repair any leaks found.
Solenoid Not Energizing
The solenoid drive signal is a 12 VDC signal. This is used to close the aspi-
rator solenoid and open the appropriate calibration gas solenoid. To test a
solenoid valve, select the Inject Cal Gas option from the Calibrate key menu
to energize that solenoid. Verify that the solenoid drive signal is present.
The aspirator air solenoid is closed when the drive signal is applied. Other
solenoids are open when the drive signal is applied (cal gas flowing). With
the drive signal present, verify the proper flow. If no signal is present,
check the interconnecting wiring between the control unit and the RCU.
If wiring is correct, replace the Auto Cal Card. If the solenoid drive signal
is present, it indicates a problem with one of the solenoid valves. Replace
the solenoid valve, being sure that the solenoid O-ring seals are properly
positioned.
To check if a calibration gas solenoid is stuck open, verify that no drive
signal is present and check for flow on the RCU flow meter. If flow is
indicated when no solenoids are energized, a solenoid is stuck open. Shut
off your calibration gases (one at a time) until the flow drops to zero. This
identifies the defective solenoid valve (replace the solenoid valve, being
sure that the solenoid O-ring seals are properly positioned).