If it is sealed then are we forgetting about the input and output math about the energy here?
If it is sealed and the heat output that is getting released into the divided environment is more than the Air Conditioners capacity, then obviously it is going to be a big issue. For one reference purpose, it is evident that there will be war between the miners and AC units in either heating up or down the room environment.

However, I am also adding one more point about "how sealed the room is?" Is it a perfectly sealed room or it does have few cracks due to door hinges, windows etc? In a small room the pressure wont be much thus outer air can easily parse through these crack openings.

If so then it changes everything about that room. In summer hot air can easily take away the coldness with it. In cold it might have some positive effects. I am sure these details will help a lot when it comes to mining operation that will be run for virtually permeant.