When troubleshooting a Rinnai HD70, most attention naturally goes to the main PCB — and for good reason, most faults do trace back there. But the sub PCB is doing an important job in the background, and when it fails, the symptoms can be easy to misread.
The P70EV-701 combines a sub PCB and surge protector in one component, doing two distinct jobs. First, it manages the electrical link to the solenoid valves via a secondary circuit board. Second, it's designed to keep the solenoid valves and the appliance's freeze protection running even if the main PCB has shut itself down after detecting a fault — a meaningful safeguard for an externally mounted water heater through a UK winter.
Its second role is protecting the appliance's main electronics from voltage spikes coming in on the mains supply, whether from the grid or nearby lightning activity. The sub PCB absorbs and suppresses these spikes before they reach the main board, reducing the risk of a surge event taking out the main PCB entirely.
⚠ Important: All electrical work on this appliance must be carried out by a Gas Safe registered engineer.
This component sits between the mains supply and your solenoid circuit, quietly absorbing surge damage and keeping freeze protection alive even when the main board has faulted out — which matters more than usual on an outdoor HD70 install through a UK winter. Fitting the genuine part restores both functions in a single component, rather than leaving the appliance's electronics and freeze protection exposed to whatever the mains supply sends next.
Order the Rinnai P70EV-701 HD70 Sub PCB & Surge Protector online today.
| Manufacturer | Rinnai |
|---|---|
| Part Number | P70EV-701 |
| Product Type | Sub PCB / Surge Protector |
| Compatible Series | Rinnai HD70 Series (REU-VRM3237 / REU-VR3237) |
| Primary Function | Solenoid Valve Circuit Continuity During PCB Fault Conditions |
| Secondary Function | Mains Surge and Voltage Spike Protection for Main PCB |
| Appliance Type | Continuous Flow Gas Water Heater |
| Installation | Gas Safe Registered Engineer Required |
