Such a system is actually a gas heating system, not a heat pump heating system. The heat generated by the combustion process is sufficient for direct heating, but the original heat pump circulation system is used as heat transfer. By using the heat transfer function, it is avoided to specially set the heating system, so that the entire heating system is compact and has high utilization rate. In the latter system, although the outdoor unit does not require two refrigerant heat exchangers, two indoor air heat exchangers are required, and the indoor air must be transported by means of pipes.
Crankcase heaters are standard equipment for some compressors. Their main function is to avoid a large amount of refrigerant being dissolved when the temperature of the lubricating oil is low, so as to ensure a good lubrication effect during the starting process of the compressor. Because if the lubricating oil contains too much refrigerant, it may cause the lubricating oil to flow out of the compressor in a large amount of foam in a period of time after the compressor is started, and the compressor is therefore in a poorly lubricated state. Obviously, the crankcase heater can generate too little heat, and the impact on the economics and technical performance of the heat pump system is almost negligible. In other words, neither the volumetric flow rate of the refrigerant nor the compression ratio of the actual operation of the compressor can be reduced.
Since the air-conditioning industry has a practice that allows the accumulated hour of the year to exceed the design temperature range, it is generally not recommended to install a crankcase heater unless specifically requested by the compressor manufacturer. This minimizes some of the problems associated with installing and using crankcase heaters.