Is it illegal for a property company to obtain an advanced refrigeration certificate without a salary increase?

Not illegal. According to Article 47 of the Labor Law, the employing unit shall independently determine the wage distribution mode and wage level of the unit according to the production and operation characteristics and economic benefits of the unit. Article 48: The State implements the minimum wage guarantee system. The specific standard of the minimum wage shall be formulated by the people's governments of provinces, autonomous regions and municipalities directly under the Central Government and reported to the State Council for the record. The wages paid by the employer to the workers shall not be lower than the local minimum wage. Therefore, it is not illegal to take an advanced refrigeration certificate without a salary increase.