There are many different options for providing conditioned air to a space. One possibility is a Direct Expansion (DX) System.
A DX system uses a refrigerant, a compound that changes phases from a gas to a liquid and back, to move heat indoors to outdoors or vice versa.
Refrigerants have been analyzed closely by environmental protection agencies. The Montreal Protocol, an international treaty designed to protect the ozone layer, was agreed on in August 1987 and began in August 1989. The goal of the Montreal Protocol is to phase out ozone depleting substances (ODS). Class I ODS, which contains chlorofluorocarbons (CFCs), were part of the first phase-out. CFCs were previously used in many applications including air-conditioning refrigerants. CFCs were 100% phased out Jan. 1, 1996. Common CFCs are shown in the image below.
Class II ODS, contains hydrochlorofluorocarbons (HCFCs), is currently being phased out and has greatly impacted the HVAC industry. A commonly known HCFC is Freon (HCFC-22 or R-22). On Jan. 1, 2010, the production, import and use of HCFC-22 was banned, except for continuing service needs of existing equipment. On Jan. 1, 2015, the production, import and use of all HCFCs were banned, except for continuing service needs of existing equipment. After 2020, the servicing of systems with HCFC refrigerants will rely on recycled or stockpiled quantities. On Jan. 1, 2030, all remaining HCFCs will be banned from production or import. Common HCFCs are shown in the image below.
The Kigali Amendment to the Montreal Protocol was adopted in October 2016. This amendment calls for the phasing down of production and consumption of hydrofluorocarbons (HFCs) by more than 80% over the next 30 years. Developed countries will begin reducing the consumption of HFCs in 2019. The amendment plans to provide financial support to countries needing it to help changeover to climate-friendly substitutes. It is expected the phase down will prevent 80 billion metric tons of carbon dioxide emissions. Common HFCs are shown in the image below.
There are several potential replacements for HFCs including hydrocarbons (HCs). The advantage of HCs is that they are not implicated in ozone depletion. They offer a cost-saving potential due to their superior energy efficiency. Some common HCs are isobutane (R600a) and propane (R290), both are used in refrigeration systems. The disadvantage of HCs is that they are flammable. Therefore, HCs are subject to international safety guidelines and legislation.
Allegheny Design Services
The next generation of refrigerants will require balancing cost, environmental impact, performance and safety.
Mechanical engineers at Allegheny Design Services are keeping a close eye on the changes. ADS can provide reliable, responsible and environmentally sound solutions during building design. We pride ourselves in offering timely solutions to complicated engineering issues, whether mechanical, electrical, plumbing or structural in nature. For MEP and structural issues, contact ADS at 304-599-0771. We look forward to working with you!
Thanks for reading,
Alex Clarkson, EIT, Junior Mechanical Engineer