Integrating Refrigerant Leak Detection into Safety Systems
Most refrigerant gas detection installations fall under the requirements of refrigeration safety standards. Examples include ASHRAE 15 in the United States and EN 378 in Europe. What these standards have in common is that the requirements on gas detection systems are not isolated from the rest of the safety protocols required to operate a refrigeration system.
One example of the integration of a refrigerant gas detector into a refrigeration safety system is the requirement to initiate mechanical ventilation fans in the event of a leak being detected. This typically applies to machinery rooms.
Another mandated requirement in certain locations, including machinery rooms and cold rooms, is the actuation of audible and visual alarms to alert personnel in the event of a refrigerant leak.
Furthermore, large or catastrophic leaks can occur in which case the mitigation required is to shut down the refrigeration system.
Going beyond safety standard requirements, many operators will integrate the output from their refrigerant gas detection system directly into their refrigeration control system. This can allow for monitoring and collation of data alongside the many other data points being gathered, such as energy performance and temperature.
Outputs from Refrigerant Gas Detectors
There is a myriad of solutions on the market that fall into the category of “refrigerant gas detectors”. Attention must be paid foremost to choosing an instrument that will effectively detect refrigerants leaks from the system to which is being applied. Closely behind that, one should consider what needs to be done in the event of a leak, and how the gas detection system supports that.
Typical output options from gas detectors can include one or many of the following outputs:
- Relays: many refrigerant leak detection systems have relays that will be triggered in the event of an alarm threshold being surpassed. Often there are multiple relays available, set for activation at warning thresholds and full alarm thresholds. The relays can be used to directly actuate ventilation fans, audio-visual alarms, or other devices. Consideration should be given to where the power for these devices comes from – a separate supply, or from the relays themselves if they are appropriate specified and rated to do so. In some cases, a simple relay output is taken as an input into control system which then initiates any further actions required
- Analog outputs: analog outputs will indicate the gas concentration detected by the refrigerant sensor. Scales include 4-20mA, 0-5V, 1-5V, 0-10V, and 2-10V. The lower and upper limits of the analog scale will equate to the lower and upper range of the gas detector. The output can be integrated into a control system for data collection and instigation of further action if a threshold set in the control system is surpassed by the analog reading. In some instances, an output outside of the scale can be used to indicate a fault status.
- Modbus: Modbus is a digital communications protocol widely used in the refrigeration industry. It allows for a communications bus to be daisy-chained across multiple refrigerant gas detectors, rather than each having a separate cable run back to a control system. Each gas detector must be uniquely addressed to identify it to the control system. A plethora of data can be gathered via Modbus. Depending on the gas detector being used, this can include information such as: alarm status, gas concentration, fault status, fault codes, service/maintenance due date, and much more. Modbus also allows the gas detector to be configured via the control system in addition to being directly configured.
Installation Considerations
In addition to considering which outputs are needed, it’s essential to factor in the ease of wiring for communication purposes. Systems with multiple cable glands and wiring terminals simplify the process of daisy-chaining power and Modbus connections, as well as linking relays for alarm and fault status, or connecting multiple outputs from one refrigerant gas detector. A streamlined wiring setup not only saves considerable time but also reduces costs during installation. By prioritizing systems with user-friendly wiring configurations, you can streamline the installation process and optimize the efficiency of your refrigerant gas detection system.