Whitepaper: Advances in Refrigerant Detection Instruments for Refrigeration Safety Compliance

| October 9, 2018

Refrigerant leak detection inside a machinery room.

There are many reasons for facilities to install refrigerant detectors to monitor for leaks in their refrigeration systems. These can vary significantly depending on the application in question. For example, the requirements and drivers for refrigerant leak detection of a supermarket with a 3,500 lb refrigeration system for cooling an entire store will be very different to those to those of a hotel room or apartment building, which will be different from industrial refrigeration for food processing and cold storage. All users of HFO refrigerants over certain system sizes are required to have monitoring for safety standards and building code compliance in order to detect leaks that could lead to asphyxiation, and heavy users of commercial refrigeration will benefit in multiple ways from detecting low level leaks.

The Cost of Refrigerant

Refrigerants costs, particularly those with a high global warming potential (GWP), are increasing. Therefore, the cost of topping-up a refrigeration system as a result of lost charge due to leaks is no longer economically viable. In the case of multi-site enterprises, such as a regional or national supermarket chain, the cost of frequent refrigerant top-ups can run into the millions of dollars per year.

Energy Consumption

Refrigeration accounts for 60–70% of the energy consumed in the typical supermarket. Depending on the system, a loss of only 15% of the refrigerant charge can decrease the systems energy efficiency by as much as 50%. This additional energy consumption can significantly affect the profits of an

Refrigerant leak detection inside a machinery room. Individual location and can dramatically more impact across a large enterprise.

Product / Service Loss

Unchecked, refrigerant leaks can result in sub-optimal operation or system failure. Such a loss of cooling can be critical for food safety and result in the spoiling and disposal of refrigerated produce, increasing waste and costing money.

Environmental Impact

Most commonly used refrigerants will have an environmental impact if released to the atmosphere, with GWPs hundreds or thousands of times that of carbon dioxide. For instance, R-410A has a GWP of 2,088 tCO2e. Regulations, such the Environmental Protection Agency’s Clean Air Act Section 608 regulate the unmitigated emissions of these refrigerants and may impose fines if refrigerant leaks are beyond thresholds.

Safety Compliance

Although most refrigerants are not acutely toxic, at high concentrations they will displace oxygen and create a risk of asphyxiation. Globally a number of standards are in place to ensure the safe use of refrigeration systems, including EN 378 in the European Union and ASHRAE 15 in the United

States. While these regulations cover the whole refrigeration system installation, they contain specific clauses that reference the appropriate use of refrigerant leak detectors aligned with alarm requirements at concentrations that do not exceed dangerous levels. There is a paradigm shift in the way users interface with instruments designed to assist with compliance concerning refrigerant safety standards as new products develop. As technology continues to advance, it is being implemented into new product design.

Refrigerant Safety Standards

Chiller Monitoring Components and Layout

Refrigerant safety standards apply across all refrigeration applications. In addition to supermarkets and hotels, Chiller rooms, data centres, transport refrigeration and industrial cold storage facilities are also regulated by these safety standards. The primary standard relating to refrigerant use in the USA is ASHRAE 15-2013. The stated scope of the standard is to establish safeguards for life, limb, health and property and prescribe safety requirements. Typically, it must be referenced in conjunction with ASHRAE 34-2013, which establishes safety classifications for refrigerants and determines Refrigerant Concentration Limits (RCL) or the threshold at which the gas concentration presents an immediate danger to health. Refrigeration system specifiers should consider the maximum system charge calculations derived from section 7 of ASHRAE 15-2013. Taking an example of a system using the refrigerant R-134a, which as stipulated in ASHRAE 34- 2013 has an 8-hour Occupational Exposure Limit (OEL) of 1,000 ppm (parts per million), which is the maximum level for human exposure over the designated period. ASHRAE 34 stipulates a RCL of 50,000 ppm. The RCL for R-134a equates to a limit of 13 lb of refrigerant per 1,000 ft3 of occupied space, as detailed with the standards. When applying the following equation, which is derived from section 7 of ASHRAE 15-2013, a refrigeration system specifier may find that the refrigerant’s RCL is exceeded in applications such as chiller rooms, or enclosed spaces such as walk-in coolers and freezers.

Maximum total system refrigernat charge (lbs)

=

(⁄1,0003) × (3)

1,000

Chiller Monitoring Components and Layout

The volume of the occupied space should be calculated in line with the guidance in ASHRAE 15-2013, section 7.3. The provisions outlined by ASHRAE 15 designate safety requirements for personnel who may be in the machinery room where a refrigerant may leak and where the total system charge of refrigerant may exceed the RCL.

Clause “8.11.2.1” states that:

Each refrigerating machinery room shall contain a detector, located in an area where refrigerant from a leak will concentrate, that actuates an alarm and mechanical ventilation in accordance with Section 8.11.4 at a value not greater than the corresponding TLV-TWA (or toxicity measure consistent there with). The alarm shall annunciate visual and audible alarms inside the refrigerating machinery room and outside each entrance to the refrigerating machinery room. The alarms required in this section shall be of the manual reset type with the reset located inside the refrigerating machinery room.

Taking the Mystery Out of Refrigerant Leak Detector Configuration

Example of aspirated refrigerant leak detection system with low minimum detectable levels.

Refrigerant leak detection systems typically fit into one of two categories:

(1) Aspirated systems with low minimum detectable levels (MDL) which are designed to catch leaks early and minimize refrigerant loss (2) Diffusion-based instruments that offer 24/7 monitoring for safety compliance purposes. The diffusion-based instruments commonly use semiconductor sensors. While this technology does not provide low MDLs, the detection capacity delivers alarms well below the thresholds stated in ASHRAE 34. This type of instrument is typically less expensive and offers less complex features when compared to refrigerant monitors are designed to reduce refrigerant loss. However, the reality is that due to the pressure on price in this sector of the market, most of the refrigerant leak detectors available for this type of application are older and are in need of modernization. These leak detectors remain very unintuitive to install, configure and maintain. This paradigm is starting to shift as manufacturers find ways to improve the interface with these instruments using modern technology. Older instruments are usually set up manually.

Typically, a combination of potentiometers, jumpers on main printed circuit boards (PCBs) and DIP switches have been used for performing vital tasks when configuring and maintaining refrigerant leak detectors, including:

  • calibration
  • setting alarm levels
  • configuring alarm behaviour (failsafe, latching acknowledgement, reset)
  • output scaling
  • alarm delay programming
  • modbus node addressing

This results in a reliance on often complex instruction manuals, reviewing PCB drawings to determine where to connect voltmeters to in order to perform the assigned task, calculations to determine what the voltages mean in the real world. Such practices can create a lengthy process and require training in order to effectively maintain instruments. Some instruments do offer a route alternative to this via using small LCD screens. While being a step forward, the number of functions that the user needs to perform can lead to complex menu structures. These lead toward continued reliance on product manuals and/or training to decipher the meaning of function codes and data assigned to items that cannot be textualized on the small screen.

New innovations eliminate the difficulties, confusion and complexity of configuring and maintaining refrigerant leak detectors. The industry is seeing new instrumentation that makes use of the ubiquitous and intuitive capabilities of the smartphone via dedicated apps and Bluetooth® connectivity. The use of an app allows for clear, organized and intuitive configuration. Where before a potentiometer would have been adjusted to a specific calculated voltage via intrusive connection to an instrument, an end user can now simply select the button in the app, which says “Alarm Level” and type in, for example, “500” to set the parts per million-alarm level to 500 ppm.

Modbus node addressing and alarm configuration can be done in a similar manner. Maintenance is also becoming more straightforward and traceable. By initiating and performing instrument calibration via a dedicated app (with, of course, the required calibration gas), calibration certificates maybe generated and sent from in the field, capturing the data on the gas used and results to provide a maintenance audit trail. Furthermore, calibration itself can be eliminated as a requirement via the use of pre-calibrated smart sensors. These smart sensors are used in a “plug-&-play” manner, requiring minimal training, taking seconds to exchange, and removing the need for maintaining, carrying and using expensive calibration gas cylinders.

Time Is Money

Refrigerant leak detectors must be configured and maintained appropriately for the application and site, as per any gas detector in any application. This is a stipulation of most regulations, in addition to a recommendation from manufacturers. Doing so requires time, which costs money. Whereas older instruments usually required training to configure and maintain, and used painstaking methods newer instruments are changing this picture. By employing technology to create non-invasive methods of checking and maintaining instruments and by taking away the time required for calibration by using pre-calibrated sensors instead and in exchange for the old sensors, time is saved. This can be in the magnitude of up to 30 minutes per leak detector reducing to 5 minutes per leak detector. Taken across a site with, for example, 20 detectors, a 10-hour workday becomes a job that takes under 2 hours, freeing resources and saving money.

About the Author

Tom Burniston is product Manager, Refrigerant Leak Detection, for Bacharach Inc. Since 2014, he has focused on the refrigerant gas detection industry. He has published numerous articles and presented papers internationally at industry events to help the refrigeration industry understand and overcome the challenges of effective refrigerant detection, the nuances of different applications and changing refrigerant regulations in Europe and the US.

About Bacharach

Bacharach is a leading provider of gas and refrigerant leak detection, combustion and emissions analysis instrumentation, energy management, and data analytics solutions for commercial and industrial applications. Bacharach products make the heating, ventilation, air conditioning and refrigeration (HVAC-R) industries safer, cleaner, and more energy efficient, enabling customers to increase productivity, reduce costs, and protect lives and the environment.

Please visit www.mybacharach.com for additional information.

Logo: – https://www.mybacharach.com/press-center/

Blog: https://blog.mybacharach.com/

Facebook: /bacharachUSA

Twitter: @bacharachUSA

YouTube: /c/BacharachInc

LinkedIn: /company/bacharachwe

Print Friendly, PDF & Email

Tags: , ,

Category: Industry News, Whitepapers

Visit Our Other Brands: