Fin-tube heat exchangers are widely used in air-source heat pumps and air-conditioners. Because these heat exchangers are comprised of a number of tubes, there are innumerable ways of organizing the refrigerant circuitry. It is important to determine the number of refrigerant circuits because the circuitry significantly influences the performance of the heat exchangers. A method for determining the optimum number of circuits is proposed in this work. This method is applied to determine the optimum number of circuits for a fin-tube condenser. The performance analyses of fin-tube condensers with various circuit configurations demonstrates that the new method is useful in determining the number of circuits required in a heat exchanger. (C) 2016 Elsevier Ltd. All rights reserved.