Specifications

Ammonia Gas Monitor – Multi Zone
Instruction 3015-5113 7
Functional Overview
General Description
Ammonia gas monitors are specified to support compliance to federal, state and local safety codes governing
emissions. Avoiding significant gas loss reduces equipment replacement costs, maintains equipment
efficiency, promotes safety, and protects the environment.
The Bacharach AGM-MZ provides continuous monitoring of ammonia gas levels in up to 16 separate test
zones. The instrument is easily programmed to monitor independent leaks (small), spills (medium), and
evacuations (large) levels that may be designated for each zone. The instrument also retains a log of
previous readings that can be easily accessed for analysis.
An audible alarm and front panel indicators are provided to signal alarm and fault conditions, and relay
contacts are provided that can be used to trigger external alarm devices in the event of a system fault, or if a
leak (small), spill (medium), or evacuation (large) level of gas is detected. The system also may be fitted with
and optional two channel 4-20mA current loop board for connection to remote monitoring equipment.
The AGM-MZ requires only minor periodic maintenance such as the occasional replacement of filters. The
monitor incorporates active diagnostics that continuously check the system for proper operation. A front
panel indicator is provided to alert an operator of system malfunctions, and fault codes are generated that
enable the user to identify the cause of the fault.
Communication Options
The AGM-MZ features full two-way communications via an RS-485 interface. MODBUS RTU is the
communication protocol standard. The instrument can be connected directly to a Building Management
System or it may be operated as a stand-alone system.
An RS-232C port is also provided for connection to a PC. This enables the AGM-MZ to be setup from a
personal computer.
Please refer to the Appendix for a more complete discussion of communication protocols.
Understanding Monitoring Levels
Effective use of this instrument requires an understanding of what constitutes reasonable alarm set points for
the ammonia gas that is monitored. Allowable exposure levels and threshold limit values in are measured 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. Bacharach has developed recommended monitoring levels based on
compliance to ANSI/BSR ASHRAE 15-1994 and ASHRAE Safety Code 34-1992. These reference levels are
listed in the Appendix.
Setting the monitor 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.
Suggested Location of Sampling Points
At the point of an ammonia leak the gas is nearly pure. As the ammonia is dispersed into the air, the gas
molecules diffuse, causing a dilution of the original concentration. The AGM-MZ measures the ammonia gas
concentration at the sample collection point. Therefore, if the termination of the collection line is not at the
exact point of the leak, the unit will read a diluted mixture of the gas and air.
It should also be noted that ammonia gas is half the density of air and tends to collect above the point of a
leak. A sample taken above the floor will have a greater concentration of gas than that collected below the
source of a leak. Sampling points should be located as close as possible to the sources of potential leaks.
If this is impractical, then the alarm set points should be adjusted for that zone to compensate for the
dilution of the gas. Sample inlet filters should be mounted close to the ceiling since ammonia is lighter than
air and rises.
. 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.