Optimizing the way we keep space cold: an overview of low charge NH3 systems

Friday, September 29, 2017

We have come to expect that large Industrial Refrigeration systems are utilizing ammonia (NH3) systems to keep their products cold, fresh and safe. The benefits of employing environmentally responsible natural refrigerants, the large range of operating temperature – as low as -60°F – and the higher efficiencies that come with using NH3 systems are undeniable

Traditional NH3 systems are not one size fits all. These are highly engineered systems that are erected on-site and become integrated into the building structure. Considering the necessary resources and time constraints involved in constructing these NH3 systems, leading manufacturers have collaborated with Danfoss on a new solution that results in faster project completion times at a lower expense, enabling a global breakthrough in low charge system solutions. 


These low charge systems offer alternative benefits to traditional large-scale systems. By virtue of Danfoss’ compact, direct weld valves and valve stations, these systems reduce leak potential and lower installation and service costs. The full range of Danfoss components in low charge systems are optimized for a wide pressure range to combine high quality with safe, reliable operation. 

Typical low charge system installations will require multiple parallel low charge systems, ranging from 5 to 60 tons of refrigeration in each, to meet the capacity required for the entire installation. Each system requires a refrigerant charge of 1 to 6 lbs. of NH3 per ton, comparing favorably to the 20 to 30lbs. of NHper ton in traditional systems. This significant charge reduction leads to less regulation and can eliminate the need for a Process Safety Management (PSM) program by keeping the total charge below the 10,000 lb. threshold. Along with this charge reduction, off-site consequence analysis, compliance costs, and liability are also all lowered. Since each system is independent of one another, the risk of a large refrigerant release is eliminated and concerns posed to the surrounding community are significantly reduced. 

The ‘one compressor per penthouse’ design eliminates the need to consistently run large compressors at part load, potentially lowering energy consumption and qualifying low charge systems for substantial utility rebates. Additionally, frequency drives are standard in most low charge systems, reducing motor speeds under part load and thus ensuring electricity usage is kept at a minimum.

Low charge systems are shipped with piping pre-welded between the compressor package, condenser and valves ready to be installed with a maximum of two welds. These systems simplify the complexity of projects even further by operating with one compressor and one condenser, which can be air-cooled on some packages. If the condenser is air-cooled, this eliminates the need for water supply piping for evaporative condensers often used in site-erected systems. 

The installed cost of low charge systems can be competitive with traditional site-erected systems, and can be reduced even further by eliminating water supply piping if air-cooled condensers are included in the low charge system design. 

Low charge NH3 systems will continue to positively impact the landscape of the Industrial Refrigeration industry. As a result of successful collaboration with leading manufacturers, Danfoss will continue to solve today’s biggest issues by Engineering Tomorrow.