The present invention relates to a method of controlling pressure maintenance equipment for a cooling and heating system. More particularly, the present invention relates to a method of operating and controlling, under optimum conditions, pressure maintenance equipment with multiple sensors so as to check for irregularities in the sensors which measure the same physical parameter. In the present invention, measurement values of two or more sensors are used to detect whether an abnormality has occurred in any sensor. If a sensor is determined to be abnormal, a measurement value of the abnormal sensor is excluded when determining a reference control value. Thereby, the pressure can be precisely and reliably controlled in response to actual conditions of the system.