Rinnai P70EV-701 Genuine HD70 Sub PCB & Surge Protector Spare Most engineers are going to focus on the main PCB when they're trying to figure out what's gone wrong with their Rinnai HD70. And let's be fair, they probably should. But there's another bit of kit that's doing a pretty vital job in the background - the sub PCB. And when this one packs up, it's not at all hard to misread the symptoms and end up with a big headache. The P70EV-701 is effectively a sub PCB and a surge protector all in one neat package. It's a pretty crucial dual role, and it's not complicated at all but it's bloody important. First off, it sorts out the electrical link to the solenoid valves - a secondary circuit board that's got to be working properly if you want to avoid problems. Then when the unit is shut down by a diagnostic code (ie, the main PCB has given up after