Trane RTWA 70-125 TON - Manual (Page 62)

62 RLC-SVD03A-EN
Module Power and Miscellaneous I/O
diagnostic suggests that there is a problem with the valve or the valve
wiring. To confirm this, it is necessary to continue the procedure. The
Electrical Integrity test will be completed in about 2 seconds. Regardless
of whether or not a diagnostic occurs, the UCM will proceed with the
stroke timing portion of the test.
Stroke Timing Test
5. At this time the UCM will drive the valve closed. Thus the total closing
time will be 25 seconds. Due to mechanical characteristics of the valve, it
will make a clicking sound when it reaches its end stops (either full open
or full closed). In most cases, the valve will already be closed when this
test is initiated, so a normally operating valve will exhibit the clicking for
approximately 25 seconds.
NOTE: The loudness of the clicking varies from one valve to another and
ambient noise can muffle the clicking sound. Therefore, it may be necessary
to use a tool to aid in the hearing of the clicking (such as a screwdriver held
between the EXV and the ear.)
6. Following the 25 seconds of closing, the valve will immediately be
stepped open for the same period of time (25 seconds). As soon as the
valve begins its opening movement the clicking should stop. while it
moves through its stroke. The service technician would then note the
time between when the clicking stopped until the time it restarts. This
would give an indication of the opening stroke time.
NOTE: If the valve and switching circuitry is operating properly, the silent
valve movement should last for approximately 15 seconds.
End of stroke clicking should then be heard for 10 seconds.
7. The module will then reverse direction and the valve will be stepped
closed again for a full 25 seconds. Since the valve should have started
from the full open position, the time to stroke closed should be noted and
it should be approximately the same as the opening time above. If both
opening and closing stroke times are correct to within ±5 seconds of the
time specified, no further testing is required. If any valve fails this test,
the service technician should perform the EXV Valve Winding Resistance
Check, steps 8 thru 10 below.
SEO EXV Valve Winding Resistance Check
1. Disconnect the appropriate EXV valve from the pin header of the EXV
module.
2. With a digital ohm-meter, check the resistance of the valve windings and
associated leads/connector by measuring the resistance of pin pairs at
the connector plug. Pin pairs are #5 and #3, #5 and #2, and #5 and #1 for
Circuit 1. Pin numbers are indicated by corresponding position # on the
board or by the raised numbers of the connector block. The resistances
should all be 40 ohms ±4 ohms at 75F winding temperature. (At a valve
winding temp of 148F the resistance would be no more than 54 ohms; at
a valve winding temp of 32F the resistance would be no less than 33
ohms).