Off-season start-ups to improve reliability of refrigerant system

Abstract

A vapor compression system includes a timer and a controller for periodically starting up the system during the off-season periods (primarily non-cooling months) in which the system would normally be shut down. This provides periodic lubrication to the compressor components and prevents severe flooded starts due to excessive accumulation of refrigerant in the compressor (compressor oil sump in particular) and other system components. Provision is also made to sequentially turn on and off system components such as the compressor, the evaporator fan and the condenser fan to enhance the system operation. The timing sequences are provided for the time intervals between the startups, as well as the off-season operation cycle times.

1 . A method of operating a vapor compression system during an off-season period during which the system is normally shut down, comprising the steps of:
 providing a timer for timing the time interval during which the system has been shut down;   starting the compressor if the time interval exceeds a first predetermined threshold;   shutting off the compressor after the time interval exceeds a second predetermined threshold.   
   
   
       2 . A method as set forth in  claim 1  and including the additional steps of starting and shutting off an evaporator fan. 
   
   
       3 . A method as set forth in  claim 2  wherein said evaporator fan is turned on and off at substantially the same times as the compressor is turned on and off. 
   
   
       4 . A method as set forth in  claim 1  and including the additional steps of turning on and off at least one condenser fan. 
   
   
       5 . A method as set forth in  claim 4  wherein said at least one condenser fan is turned on after the compressor is started. 
   
   
       6 . A method as set forth in  claim 4  wherein said condenser fan is turned off before the compressor is turned off. 
   
   
       7 . A method as set forth in  claim 1  wherein the additional step is provided of sensing at least one parameter to determine whether the compressor startup is required. 
   
   
       8 . A method as set forth in  claim 7  wherein said at least one parameter is selected from the group consisting of: ambient temperature, indoor temperature, suction pressure, discharge pressure, saturation suction temperature, saturation discharge temperature or a combination of thereof. 
   
   
       9 . A method as set forth in  claim 1  wherein the timer setting is determined by at least one parameter. 
   
   
       10 . A method as set forth in  claim 9  wherein said at least one parameter is selected from the group consisting of: ambient temperature and indoor temperature. 
   
   
       11 . A method as set forth in  claim 1  wherein the first predetermined threshold is between 2 days and 4 weeks. 
   
   
       12 . A method as set forth in  claim 1  wherein the second predetermined threshold is between 2 and 15 minutes. 
   
   
       13 . A vapor compression system, comprising:
 a compressor for compressing refrigerant;   a condenser for rejecting heat of compressed refrigerant;   an expansion device for expanding the compressed refrigerant to a lower pressure and temperature;   an evaporator for receiving refrigerant from said expansion device and then transferring heat from air to be cooled to the refrigerant;   a timer for determining a period of time during which the vapor compression system has been shut down; and   a controller for starting the compressor after the system has been shut down for a predetermined period of time.   
   
   
       14 . A vapor compression system as set forth in  claim 13  wherein an evaporator fan is operatively associated with said evaporator and said controller also turns on and off said evaporator fan. 
   
   
       15 . A vapor compression system as set forth in  claim 14  wherein said controller turns on and off said evaporator fan at substantially the same times as it turns on and off the compressor. 
   
   
       16 . A vapor compression system as set forth in  claim 13  wherein a condenser fan operatively associated with said condenser and said controller also turns on and off said condenser fan. 
   
   
       17 . A vapor compression system as set forth in  claim 16  wherein said controller turns on said condenser fan after it has turned on said compressor. 
   
   
       18 . A vapor compression system as set forth in  claim 16  wherein said controller turns off said condenser fan before it turns off said compressor. 
   
   
       19 . A vapor compression system as set forth in  claim 13  and including at least one sensor for sensing at least one parameter to determine whether the compressor startup is required. 
   
   
       20 . A vapor compression system as set forth in  claim 19  wherein at least one parameter is selected from the group consisting of: ambient temperature, indoor temperature, suction pressure, discharge pressure, saturation suction temperature, saturation discharge temperature or a combination of thereof. 
   
   
       21 . A vapor compression system as set forth in  claim 13  wherein the timer setting is determined by at least one parameter. 
   
   
       22 . A vapor compression system as set forth in  claim 21  wherein at least one parameter is selected from the group consisting of: ambient temperature and indoor temperature. 
   
   
       23 . A vapor compression system as set forth in  claim 13  wherein the period of time during which the vapor compression system has been shut down is between 2 days and 4 weeks. 
   
   
       24 . A vapor compression system as set forth in  claim 13  wherein the vapor compression system operation between consecutive shutdowns is between 2 and 15 minutes.