I am a subway enthusiast. As a young boy, I lived in The Bronx and rode subways as a way to get around the city. Now, living in Kansas City, my interest in the lore and functioning of this incredible system continues. From a firsthand perspective, I can assure you that air conditioning for subway cars is an important development.
photo: John Urbanski
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If someone offered you an air conditioner that could keep 200 people in a room cool and relaxed in the middle of a hot summer day, and still be compact enough to allow technicians to replace it with a an overhead hoist: in which office building would you want to look to see this marvel move its air?
Now suppose this same person assured you that the air conditioner wouldn’t miss a step at 50 mph?
Obviously, we're not talking about an office building. We are talking about the latest generation high-tech New York City subway car. Manufactured by Bombardier Transportation, the R142 subway car is 51 feet long and nearly ten feet wide and weighs 40 tons. First tested late in 1999, the R142 runs in consists of ten cars each on one of the world’s busiest subway lines. At rush hour, each car might carry as many as 200 crushed straphangers.
Keeping these busy commuters from losing their cool on a sweltering, 90 degree day offers special challenges far beyond heat removal. Subway trains accelerate and decelerate hundreds of times a trip, subjecting the climate control system to positive and negative G-forces, vibration and swaying. The trains operate year-round, so the ventilation system must be ready for all seasons.
As the trains climb onto elevated lines, they encounter dust, rain, snow and ice, all of which find their way into air intakes and accumulate in pools within the air conditioner. Additionally, since MTA New York City Transit considers fire the most serious danger to passengers underground, it demanded the air conditioning be fire-resistant, even in the presence of arcing from the 600 volt third rail and flammable materials that may have been brought aboard the train.
To meet these challenges, Bombardier designed a roof-mounted, 6.5 ton air conditioning unit. Bombardier needed a powerful, yet efficient fan and duct system, and to get it, the world-famous passenger railcar manufacturer turned to Multifan USA, the Bloomington, Illinois-based subsidiary of Vostermans Ventilation B.V. in the Netherlands and IBT, Vostermans’s master distributor in Kansas City.
Vostermans Ventilation delivered an innovative, integrated Multifan fan for the condenser unit that moves 150 m3 of fresh air per minute as the train carries its load at up to 50 mph, while filtering dust and diverting water and ice by harnessing the air pressure supplied by the unit itself and some simple physics. Moving all that air is a three-phase 460-volt AC motor, which turns a 24-inch fan at up to 1,000 rpm.
The unit is also rugged and simple to maintain. MTA New York City Transit’s workers can swap it out of the railcar in under an hour without taking the train to a heavy overhaul shop. In a subway system that moves over five million people a day through 468 stations, that is more than a convenience; it is a necessity. Today, over 1,000 R142 cars are in daily service in New York. In 2006, the R142 averaged nearly 190,000 miles between trips to the repair shops. Compare that to the average pickup truck!
Bombardier's refrigerant compressor can run in reverse as well, allowing Bombardier's unit to act as a heat pump in winter, should its transit authority customer request it.
That cool subway train turns just as comfortably warm on a white winter day. And that’s the way customers like it!
