Low-charge ammonia: Taking industrial refrigeration by storm

But how should it be defined – by total charge or charge/capacity ratio?

Low charge ammonia (NH₃) is increasingly a topic of interest and importance to the industrial sector. The applications are getting bigger and the charges are getting smaller.

Having less of the toxic refrigerant in the system is a great advantage for a system’s safety and its susceptibility to regulatory standards. The former “more is better” philosophy when it comes to the charge is getting rejected. Increasingly, all but the essential charge gets eliminated and the heat transfer to a secondary fluid or the air is maximised. Terry L. Chapp discusses this development in a white paper (download the paper below the article).

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The actual size of the ammonia charge in any given facility has come under a large and expansive examination by regulatory authorities, communities, and insurance providers.” –– Terry L. Chapp

Chapp describes the technological advancements that allow decreasing the charge.

These are:

Advanced controls for precise liquid metering
Advanced heat-transfer technology with higher heat-transfer coefficients
Advanced manufacturing technology providing better components
Advanced auxiliary components optimised for the refrigerant

However, there is an open question about low charge ammonia: What exactly is low charge? To answer this question, two major viewpoints are being discussed. Some people argue that the definition should be based on the specific charge per system used and the cooling power provided. Others say that the total amount of refrigerant used is sufficient.

sheccoBase, the market research body of shecco (publisher of this website), will publish the World Guide to Low Charge Ammonia this year. During ATMOsphere America 2018, Derek Hamilton from sheccoBase presented a preview of the guide’s findings. One aspect was the definition of low charge. sheccoBase did a survey and found out that 65% of the respondents favour a definition based on the specific charge of the system without reference to capacity.

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The majority of people responded to the survey favor a definition based on specific ammonia charge, rather than relative to the cooling capacity” — Derek Hamilton, shecco

During the same conference, professor Pega Hrnjak, co-director of the Air Conditioning and Refrigeration Center (ACRC) at the University of Illinois, and founder and president of R&D company Creative Thermal Solutions (CTS), shared his thoughts about the topic. He observed a “race” by companies to call their units ultra-low or low charge ammonia. He also stated that the U.S. Environmental Protection Agency (EPA) does not require a leak reporting of less than 50 kg of NH₃. Hrnjak argues that a definition of maximum allowable charge (like the limit placed on hydrocarbons in self-contained systems) is needed to decrease regulatory burdens. This will help maximise efficiency and capacity, and move the technology forward.

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That was in ASHRAE 15 – 5 to 6 pounds [maximum] in the building and that will allow ammonia to be seen as a normal refrigerant. This will be a boost to the technology.” — Pega Hrnjak, CTS

However the definition may be, companies such as Scantec or EVAPCO promise energy savings from lowering the charge. Safety will also be increased as less refrigerant can leak. NH₃ is a climate- friendly and viable alternative for HFCs, which are potent greenhouse gasses (GHG) and contribute to global warming.

To find out more about low charge installations, read the articles below.

Scantec: ‘Adopt low-charge NH₃ to comply with HFC phasedown’