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posted November 11, 2013
Toronto has more outdoor compressor-cooled rinks than any city in the world Ė 52. But our civic knowledge of the physics of ice maintenance hasnít kept pace with our collective rink wealth. Many people seem to find it amazing, even shocking, that outdoor rinks can be skateable when the air temperature is above freezing, as high as 11 or even 15.
Whatís the surprise? Collectively, as taxpayers, we spend about $500 a day at each rink to fuel the compressors that cool the rink pad. The rink compressors vary between 100 and 200 horsepower each Ė you can hear their noise through the compressor-room doors at the sides of the buildings. These compressors push a brine (salt water) solution through a big tank of cooling ammonia, and then out into the extensive grid of PVC pipes underneath the concrete floor of the rink. The cold liquid brings the entire big concrete slab to well below freezing, so any water thatís put on the surface of the rink pads sets up as ice right away. The brine liquid in the pipe grid circulates back into a large pipe in the ďheader trenchĒ right next to the building, underneath where everybody stands when the zamboni is doing ice maintenance. From there the brine gets pushed back into the compressor room, where it passes through the freezing-cold ammonia tank, and out again into the pipes under the concrete, and so on.
The only serious match for this powerful cooling system is the sun, and in the months on either side of the December 21 winter solstice, the sun is very weak. It doesnít get to spend very much time above the horizon, and that suits the compressors just fine.
The sun begins to gain real power toward the end of February, which is why, on a sunny day on, letís say, February 25, when the air temperature is minus 8, the ice gets really mushy near the reflective boards, and even a bit soft in the middle. The compressors are losing ground as the sun prepares to bring on spring and summer. But on a low-sun Monday in November even at 11 degrees, a thin film of water forms on top of solid ice, and the shinny hockey and pleasure-skating are brilliant.
Itís not only rink users whose rink literacy is in some need of upgrading. The cityís rink staff are also confused. In our travels around the city's outdoor rinks, we have heard some zamboni drivers say that they canít make ice because the temperature is above zero. Over the years, the cityís Parks management has blamed a multitude of ice-making sins on the temperature, global warming, etc. Convenient - but most of the time, not true. The compressor-cooled rinks can do their job, and having all those rinks can take some of the sting out of the dark months of winter for Torontontians.
The science is there, the history is there (pre-amalgamation), professionals say it can be done, Harbourfront is doing it, even volunteers have done it. This list supplies the fundamentals of ice making.