As always with me, a little knowledge is a dangerous thing, but let me express my views on train and tram air conditioning.
As the temperature rose to 43 degrees today and trains failed one after another, we are told by Metro Trains that the Comeng train air con system was not designed to operate above 35 degrees. We were told this by the previous company Connex. We have been told this by the state government. Temperatures of 35 degrees plus happen every summer in Melbourne, so I am not sure why they would not be 'designed' to cope.
While the controls of an air con unit can be quite a complex piece of electronics, the basics are not. You have a compressor and a fan. Compressed gas gets cold and a fan blows through the cold area and blows out cold air into your room or vehicle, car, train, bus or tram.
The size of the compressor and the ability of the fan to distribute the cool air should be matched to the the size of the area cooled and the conditions of the area. Clearly a moving vehicle with opening doors and full of people will need to get more cooling than a a single room in a house.
Melbourne's Combino trams, the newer ones that operate in St Kilda Road and Swanston Street very obviously have inadequate air con systems. If you listen carefully on a warm day, you can hear the system cut in and out. If you listen on a hot day, you will not hear the system cut out and yet the tram is uncomfortably warm. Inadequate air conditioning. Trams with air systems designed for Germany do not have appropriate air conditioning for Melbourne.
Adelaide also bought new trams four or so years ago. They too were Euro designed and had inadequate air conditioning. Passengers were blamed for not having eaten breakfast and fainting. Remedial work was done, haha, putting heavier tinting on the windows. Eventually the government bit the bullet and spent millions on upgrading the tram air conditioning. Adelaide has bought even more new trams and retired its very old fleet. I will bet that their newest trams do have adequate air conditioning.
I have not been on one of the French trams, the Citadis that also operate in Melbourne, on a really hot day, so I can't speak for them, except that on a warm day, they seem ok.
Melbourne's B class trams, the older articulated trams have excellent air conditioning. It is a bit noisy but also easy to hear when it cuts in and out. Even when the weather is quite warm, it still cuts out at times, and yet the tram remains deliciously cool inside.
Our trains, of the three different main types, are very comfortable with working air con. The older Comeng trains are the ones with air con that is 'only designed to operate' up to 35 deg.
Back to the tech. In a big area that has inadequate air conditioning, the compressor will just work non stop. That is, it is running at full capacity and can do so for a long time, until it is either switched off or the weather cools down. If it runs non stop, it will wear out more quickly than if it was cutting in and out at regular intervals, but that is a long time.
This is what they are designed to do. That is, run for long extended periods. I just cannot possibly imagine why these Comeng train air conditioners keep failing and after being in service for such a long time, a fix for the problem hasn't been found without an expensive upgrade.
I am afraid I just do not believe the phrase, 'designed to operate up to 35 degrees'. I would believe 'designed to cool efficiently up to 35 degrees'.