Refrigeration heat pump and auxiliary heating apparatus control system with switchover during low outdoor temperature

A control system for controlling a refrigeration heat pump apparatus and an auxiliary heating apparatus for reducing the change in controlled space temperature when the system switches from control by refrigeration heat pump appratus and auxiliary heating apparatus to control by auxiliary heating apparatus alone, comprising,

• space temperature responsive means having a first temperature responsive means for controlling in a first range of temperatures, a second temperature responsive means for controlling in a second range of temperatures, said first and second ranges of temperature are separated by a temperature differential, first anticipation circuit means operated by said first temperature responsive means and second anticipation circuit means operated by said second temperature responsive means,
• control apparatus comprising first relay means adapted to control the operation of the heat pump apparatus and second relay means adapted to control the operation of the auxiliary heating apparatus,
• outdoor temperature responsive means,
• changeover relay means connected to be energized when said outdoor responsive means responds to a temperature below a predetermined temperature,
• circuit means including said changeover relay means when the heat pump apparatus is to operate for connecting said first temperature responsive means to said first relay means,
• second circuit means including said changeover relay means when the heat pump apparatus is to operate for connecting said second temperature responsive means to said second relay means,
• third circuit means including said changeover relay means when operated at a predetermined outdoor temperature connecting said second relay means to said first temperature responsive means, deactivating said heat pump and disconnecting said second relay means from said second temperature responsive means, and
• means including said changeover relay means for connecting said first and second anticipation circuit means to be controlled by said first temperature responsive means to reduce the amount of change in controlled space temperature when operation is transferred from said second range to said first range.