Compressor crankcase heating control systems and methods

#The present disclosure relates to compressors and more particularly to heater control systems and methods for use with compressors.

#The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.

#Compressors may be used in a wide variety of industrial and residential applications to circulate refrigerant within a refrigeration, heat pump, HVAC, or chiller system (generically “heat pump systems”) to provide a desired heating or cooling effect. In any of the foregoing applications, the compressor should provide consistent and efficient operation to ensure that the particular heat pump system functions properly.

#The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein:

#FIG. 1A is a functional block diagram of a first example heat pump system according to the present disclosure;

#FIG. 1B is a functional block diagram of a second example heat pump system according to the present disclosure;

#Compressors may include heating elements that heat crankcases in order to avoid problems related to “cold starting” or “liquid flood-back.” “Cold starting” may refer to startup of a compressor when lubricants within the compressor are cold and diluted by refrigerant. The lubricants therefore are less viscous and have lower lubricating capabilities during cold starting, which may cause higher stress on one or more compressor components, such as a bearing.

#Heating the crankcase of a compressor increases a temperature of lubricants inside the crankcase. Increasing the temperature of the lubricants may improve performance and/or prevent damage to the compressor due to the increased viscosity of cold lubricants. “Liquid flood-back” may refer to when liquid migrates into the compressor shell. Liquid migrates back to a compressor when the compressor is off and the compressor temperature is less than (its surrounding) ambient temperature. Heating the crankcase of the compressor may minimize liquid migration to the compressor and may remove liquid that has migrated to the compressor.

#Typical crankcase heating elements, hereinafter referred to as “crankcase heaters,” may operate in different ways. For example, a crankcase heater may run continuously while the compressor is in an off state (i.e., not compressing). Continuous use of a crankcase heater while the compressor is in the off state may heat the lubricant more than is required to avoid “cold starting.” However, this continuous use of a crankcase heater is less efficient than desired due to wasted energy from excessive heating.