From the plans, it appears that there was a boiler room in the basement too, and is likely what fed the radiator seen in the picture. I doubt whether the compressors in the room directly behind the wall were running, since the refrigerators appear to have their own compressors in a separate room. Being 28 outside, I don't think they would have used air conditioning, even with the large crowd inside. A running methyl chloride system would have a high discharge temperature, according to the sources I found, in the neighborhood of 170-180 degree compressor discharge temperature. Methyl chloride will also self-ignite in the presence of aluminum. I don't know very much about the construction of a comfort air conditioning system back then, but I doubt that they would have remotely located evaporators like shown in the picture, especially since it appears from the pictures that there was a forced-air system in place