Xylem XL Series H-522 - Plus - Manual (Page 230)

21-4 Operation with the H-355 "Smart Gas" System
XL™ Series
PC Interface View Built In Display Screen
Purge Pressure Purge Pressur[XXX]/Min
This is the pressure that the H-355 uses to purge the orifice line. The range is 15 to 80 PSI. This
must be set higher than the purge threshold if the auto purge option is enabled. When adjusting
the purge PSI the purge duration will automatically change to make sure it is set long enough to
handle the new purge pressure.
When the H-355 purges it sequences through a series of operations. First it isolates the sensor
from the pressure line to protect the sensor from the high purge pressure. Then the compressor
turns on and builds the pressure up to the level indicated by this option, “Purge Pressure.” When
the pressure is at the desired level another valve opens applying the full tank pressure to the
orifice line without any restrictions. The line is now being purged. The purge will continue for
several seconds based on the value in the “Purge Duration” option. After the purge, the purge
valve is turned off and the line pressure is again applied to the sensor. The compressor may turn
on again if needed to maintain the desired bubble rate. If the compressor does turn on it is a good
indication the purge duration is set long enough to properly purge the line and return to normal
operation. If the compressor does not turn on after the purge then increase the purge duration by
10 or 20 seconds to make sure the line pressure has stabilized.
PC Interface View Built In Display Screen
Purge Duration Purge Time: [XXX]sec
This is the duration of a purge in seconds. The range is 30 to 240 seconds. Higher purge pressure
values require more time for the purge to complete properly. If the purge time is too short the
pressure in the tank will be abnormally high causing a much higher bubble rate. The abnormally
high bubble rate may cause stage readings that are slightly higher than expected. If the H-355
compressor turns on after the purge is done then the purge time is long enough. The worst case
would also be at lower water levels as more air would have to be released from the tank. The
purge duration is set automatically when ever the purge pressure is changed. The following table
shows the minimum time to build up the purge pressure, the minimum purge duration that should
be used based on purge pressure and the total minimum time a purge should take based on the
different purge pressures. Note that battery conditions, orifice line length, temperature and other
factors may affect these times.