Rinnai PA-700 A Series PCB - The Genuine Article The PCB on the Rinnai Infinity A Series is the brains of the operation - the bit that keeps your water heater up and running - from detecting that water's flowing to firing up the ignition, to dialling back the gas valve, giving the combustion fan a bit more or less oomph, and keeping an eye on all the safety systems. It's all run through this single board. The Infinity A Series range is designed specifically for the UK domestic market - these are ErP A-rated continuous flow gas-fired hot water heaters that promise high efficiency and low running costs, on top of giving you exactly the right temperature water when you need it. And it all comes down to the PCB not working right - if the board develops a fault, the appliance starts to lose control, and without the right diagnosis and a genuine replacemen