Innovative Conversion Program Targets HCFC-22 Rinks

The City of Montreal has been moving forward with a cooling system conversion program for rinks still using HCFC-22 refrigerant. This motivated in part by the pressures of the Montreal Protocol, which will result in the phase out of HCFC-22 by 2020.

The City owns and operates 47 rinks: 41 inside and six outside. Currently, 13 rinks use ammonia (R-717), one is now in conversion, eight are in the design or quotation stage, and 29 are still chilled with HCFC-22. The conversion rate target is four arenas per year. 

Current study

Aware of the breakthroughs that carbon dioxide (CO2) systems have made in the cooling industry, the City asked the Natural Resources Canada’s CanmetENERGY Research Centre to investigate the technology, and provide a comparative study against other available technologies. Ammonia (NH3) is currently the  standard for its rink fleet.

“It is important to adopt a standard design for our rink upgrade project; for environmental, energy, economic and maintenance concerns,” explained Claude Dumas.

Acknowledgment

The DSTI Services selected the R-717 after consulting the Montreal Public Health Department (PHD) and the Civil Security Centre (CSC). Its standard design has also been acknowledged by the Commission de la santé et de la sécurité du travail (CSST) and the Association québécoise pour la maîtrise de l’énergie (AQME).

The City was a finalist at the 2012 Quebec Heath & Safety Great Awards for its new air cleaner device specially designed for the purpose of cleaning the mechanical room in the case of an ammonia leak. It also received Sustainable honours at the AQME’s 2012 Énergia Gala for its Rink Conversion Program.

Recommendations

As the arenas are located in densely populated areas, the City has had to review the usual design for ammonia-based cooling systems. The first goal was to decrease the refrigerant load. “Our systems use a critical load of 250 lb. (113 kg) of ammonia for a cooling capacity of 71 RT (249.6 kW), which reduces the risk in case of a leakage,” said Costas Labos. As such, the installation of a U shape droplet separator (see Figure 1) helps to reduce the refrigerant load even more, down to 100 lb. (45.3 kg) while minimizing the footprint.

“In addition, by separating the class T mechanical room in two areas – engine room and control room – it’s possible to create a pressure differential between both rooms, isolating the cooling appliances from the electrical and control devices, which increases the personnel safety,” added Dumas.

The development of a closed-loop oil recovery system – another original design by the city of Montreal – reduces risk during maintenance work and allows the recovering and recycling of compressor oil. In addition, brine is run through the cooling slab in four short loops. Developed by the city in 1991, this innovation is now a design reference for other arenas.

Special Applications

In order to optimize system operation, two ammonia heat pumps were installed for heating in Pierre “Pete”-Morin and Père-Marquette arenas in 2012. Their reliability and coefficiency of performance (COP) are now under analysis.

Dumas is waiting for the CanmetENERGY research results, which will be released this summer, to comment on the report that will compare technologies using NH3, halocarbons and CO2, in terms of viability, resistance and safety. Developed for the agri-food industry, the CO2 technology is relatively new for rink applications, and the City of Montreal’s questions and concerns have not all been answered. <>

Luc Boily is the managing editor of Plomberie, Chauffage et Climatisation (PCC), HPAC’s sister publication. He can be reached at lboily.pcc@videotron.ca.