Adding a third fan to the NH-D15 G2 will usually only provide small performance improvements but increase noise emission significantly, so we do not recommend adding a third fan unless you prioritise cooling performance over acoustics. If you would like to add a third fan, we can send you fan clips free of charge and recommend the NF-A14x25r G2 PWM as it will provide the smoothest acoustics in combination with the stock PPB/PPA models. Please use our fan clips order form to order the clips free of charge.