A method of operating a heating and cooling system, including (1) providing a heating/cooling apparatus comprising first and second heat exchangers, (2) providing a conduit module modularly coupled to the heating/cooling apparatus and adapted to be coupled to a plurality of fluid circuits for heating and/or cooling loads, and (3) operating a control system configured to operate the conduit module in a plurality of heating and/or cooling modes. The conduit module is positioned between the heating/cooling apparatus and the plurality of fluid circuits. The conduit module includes first, second, and third supply conduits and first, second, and third return conduits, to convey first, second, and source fluids to and from respective first, second, and source fluid circuits. The conduit module includes first, second, third, and fourth three-way valves to selectively regulate flow of the first, second, and source fluids.