Method and device for controlling the operation of a heat pump device

Method for controlling operation of a unit heat pump (10A) using NH3 as a refrigerant, has a compressor (16, 44), a condenser (18, 46), an expansion valve (20, 50) and evaporator (54), and constitutes one cycle heat pump, with the compressor a reciprocating compressor (16) having a plurality of cylinders, a drive motor (24, 45) which actuates the pistons of the cylinders, and having also pump lubricating oil (28) driven by the drive motor (24, 45), the method comprising: a first step of detecting the temperature of the fluid heat exchange in a condenser outlet (18) or the evaporator (54), the fluid exchange heat with the refrigerant termopermutado NH3 in the condenser and evaporator; a second step of maintaining the temperature of the fluid heat exchange in the condenser outlet (18) or the evaporator (54) so ​​that it is within a setting range by controlling, in operation with all cylinders, the capacity of the reciprocating compressor in a period between a maximum load and a minimum load for lubrication, in which the flow of a pump oil lubrication can be ensured, based on the control of the revolution speed of the drive motor (24 ) driving the reciprocating compressor (16); and a third step of maintaining the temperature of the fluid heat exchange in the condenser outlet (18) or the evaporator (54) to be within the range set by controlling the capacity of the reciprocating compressor (16) the minimum lubrication or lower load based on a combination of control of decreasing the number of operating cylinders and controlling the revolution speed of the drive motor (24).