Abstract: The invention relates to apparatus for heating and/or cooling a room which is large enough to require at least two heat exchanger units. Controls are provided which dependingly relate the outgoing air stream temperatures of the heat exchangers to avoid the causing of drafts in the room. One of the heat exchangers is a guide unit and all others are follower units. Each heat exchanger has its own individual control such as a valve for admitting heat exchange fluid to the unit. The guide unit has associated room temperature sensor and setting devices for controlling its individual control. Each follower unit has a pair of temperature sensors for jointly controlling its associated individual control. One sensor of each pair is in the outflowing air stream of the guide unit and the other sensor of the pair is in the outflowing air stream of the associated follower unit.