Rinnai N Series PCB - Your Best Bet If You're Having Problems With Yours (PN-700) The Rinnai PN-700 PCB is the proper replacement control board for your Rinnai N Series water heater. This thing is the brains behind the operation - the electronic control unit that runs all the key functions like ignition, temperature control, fan operation and safety checks. In other words, it makes sure all the bits work together nicely, and that the water heats up to the right temperature. Deep down inside your Rinnai system, the PCB is chatting away to various sensors and components like thermistors, ignition systems and gas valves, making sure everything keeps going smoothly - until the control board packs up or gets damaged that is. And if it does go wrong, your appliance might start chucking out fault codes, or just stop working dead in its trac