System and Method for Oil Return in an HVAC system

摘要

A system and a method are provided for returning oil in a heating, ventilation, and air conditioning (HVAC) system by determining when an ambient zone temperature is equal to or less than a temperature limit and reversing a direction of refrigerant flow of the HVAC system based on the length of time. Also, a system and a method are provided for monitoring the length of operation in a first and a second heating mode and for reversing a direction of refrigerant flow based on the length of time operation occurs in the first and second heating modes. A system and a method having a first compressor, a first heating mode, a second heating mode, a defrost mode, and a controller is disclosed. The controller selectively controls initiation of the defrost mode in response to an HVAC system operating in a heating mode of operation for a predetermined amount of time.

主权项

1. A heating, ventilation, and air conditioning (HVAC) system, comprising:
a processor configured to determine when an ambient zone temperature is equal to or less than a first temperature limit; a processor configured to calculate a first length of time using a first timer, the first length of time being the length of time that a first compressor operates at a first capacity to deliver refrigerant to a first circuit of a first heat exchanger and during which operation the ambient zone temperature is equal to or less than the first temperature limit; a processor configured to initiate reversing a direction of refrigerant flow of the HVAC system when the first length of time is equal to or greater than a first time limit; a processor configured to determine when the ambient zone temperature is equal to or less than a second temperature limit, the second temperature limit having a value higher than the value of the first temperature limit; a processor configured to calculate a second length of time using a second timer, the second length of time being the length of time that the first compressor operates at a second capacity to deliver refrigerant to the first circuit of the first heat exchanger, the second capacity being different than the first capacity, and during which operation the ambient zone temperature is equal to or less than the second temperature limit; and a processor configured to initiate reversing the direction of refrigerant flow of the HVAC system when the second length of time is equal to or greater than a second time limit.