Emerson GW-810-3760, Инструкция по установке и эксплуатации

Страница: 11 / 88

4 • RLDS I&O Manual 026-1309 Rev 11
2.3. Understanding
Monitoring Levels
Effective use of this instrument requires an
understanding of what constitutes reasonable alarm
setpoints for the type of gases being monitored.
All AC&R systems leak some refrigerant. Refrigerant
manufacturers define allowable exposure levels and
threshold limit values in units of parts per million
(PPM). In a good “tight” installation these
background levels will be acceptably low and often
do not require corrective action. You can reduce
nuisance alarms and needless service calls if the alarm
levels are set at practical limits.
Recommended monitoring levels based on
compliance to ANSI/BSR ASHRAE 15-2007 and
ASHRAE Safety Code 34-2007 have been developed
and are listed in Appendix A: Recommended
Refrigerant Gas Alarm Settings Section .
Setting the unit at these recommended alarm levels
will satisfy the needs of most users. However, the
PPM levels generated by system leaks into the
environment are greatly influenced by the volume of
air in the sampling area, air circulation, size of the
leak, distance to the monitoring point, and a host of
other variables. In some cases the set points may need
to be adjusted either up or down to achieve effective
monitoring. Please contact your representative ( 770-
425-2724 ) for assistance in obtaining these levels.
2.4. Response to the
Presence of Multiple
Refrigerants
The RLDS is a refrigerant level monitor, not a gas
analyzer. You must program the monitor to test for a
specific refrigerant in each zone, and it will only
return accurate concentration readings for that
particular refrigerant. If a leak occurs of another
refrigerant gas type, the monitor may return incorrect
readings.
Most applications only require detection of a single
refrigerant and the problems that are associated with
monitoring multiple gases are rarely an issue. If there
is a possibility of multiple refrigerants leaking in the
same sampling zone, you should carefully consider
which refrigerant compound you program the unit to
monitor.
2.5. Suggested Location of
Sampling Points
At the point of origin of a refrigerant leak, the gas is
nearly pure (highly concentrated). As the refrigerant
is dispersed into the air, the gas molecules diffuse,
causing a dilution of the original concentration. The
RLDS measures the refrigerant concentration at the
sample collection point, so if the termination of the
collection line is not at the exact point of the
refrigerant leak, the unit will read a diluted mixture of
the refrigerant gas and air.
Gases of interest may be heavier or lighter than air
and may collect above or below the point of the leak.
Therefore sampling point placement is critical and
must take into account properties of the target gas and
air flow within the space.
DO NOT block any of the zones. Unused zones may
be disabled by setting the distance parameter to zero
feet in the zone setup screen.
The RLDS should be centrally located in the
mechanical room and be readily accessible for easy
visual monitoring and servicing. The combined
length of sample tubing, plus exhaust tubing, should
not exceed 1200 feet (366 meters) for any zone. The
fresh air purge line should draw from an area that does
not contain any gas other than fresh air. The exhaust
line should run to an outside location if possible.
Ideally, two to three pick up points spaced around
each chiller will provide sufficient coverage. It may
Leak Detector Gas Type Sampling Point
Location
Multi-Zone Halogen Mount sampling
points 6-18 inches
above floor
Multi-Zone CO2 (Carbon
Dioxide)
Mount sampling
points 4-6 feet above
floor (breathing zone)
Table 2-1 - Sampling Point Locations
NOTE: The combined length of the purge line
and the exhaust line cannot exceed 500 feet
(152.4 meters).