REFRIGERANTS
Safety compliance versus leak reduction
Ken Easterday, product manager – fixed instruments at Bacharach looks at mechanical and machinery room refrigerant monitoring.
I
n commercial chiller and refrigeration rack applications, most refrigerant gas detectors currently specified for refrigeration equipment in the industrial safety
standards will provide gross levels of safety protection from large refrigerant leaks but are ineffective at providing an early warning of the most common refrigerant leaks. Ultrasensitive, multi-point refrigerant gas detection systems have been successfully used to achieve both occupant safety AND early warning leak detection that enable emissions reduction, cost savings, improved maintenance, and efficiency of cooling systems used in commercial buildings.
Concentration limits from ASHRAE 34, CSA B52 and EN 378.
Safety Requirements Industry standards have mostly harmonized around the design, operation, and maintenance of commercial refrigeration systems in mechanical rooms. ASHRAE 15 and 34 (United States of America), EN378 (European Union) and CSA B52 (Canada) guide the industry in their jurisdictions and are focused on the safety of operators and any person that may have access to or potentially have access to the mechanical room equipment where refrigerant gases may be present. These standards outline the proper use of equipment that contains refrigerants, the amount of charge for specific refrigerants and the exposure limits of refrigerant gases. These safety standards are further augmented by the International Fire Code and International Mechanical codes and in local jurisdictions. In addition to the safety standards above, EPA 608 (USA), CARB (California, USA) and F-Gas (EU) governmental regulations and laws outline the overall reduction of high GWP (Global Warming Potential) and ODP (Ozone Depletion Potential) refrigerants that are harmful to the environment. Most commercial buildings today, should have some
form of refrigerant gas detection in their mechanical rooms to protect the safety of personnel who may be working in and around refrigeration equipment. It’s important to understand the difference between the purpose of refrigerant gas detection used to meet safety standards and the type of refrigerant gas detection used to provide early warnings of leaks and reduce refrigerant emissions as provided by regional government regulations.
Safety based diffusion gas detection vs. ultrasensitive sampling system
Most refrigerant gas detectors that are used to meet mechanical room safety requirement are diffusion-style gas detectors. They are commonly wall mounted requiring the gas leak to reach the sensor element while the gas concentration will become less concentrated from the point of the leak to the location of gas detector. Once the gas is detected they can alarm quickly. If an IP rated enclosure is used then the response times could be longer. Safety based, diffusion detectors typically incorporate a gas sensor with a minimum detectable limit (MDL) of 100 PPM and preset alarm settings of 15% to 100% of the full scale range. Limiting the low alarm range reduces false alarms while still providing for a safety factor of about 7x before reaching the threshold of the OEL (Occupant Exposure Limit) which is the range of the typical high alarm setting. This safety factor becomes greater when considering that the OEL is typically used as the TLV-TWA (threshold limit value – time weighted average) and is defined as 8-hour time-weighted limit. The aim of the safety standards is to give warning to a technician or other commercial building employee before walking into a mechanical or machinery room where the refrigerant gas concentration may exceed safe
34 March 2021
www.acr-news.com
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