Solar diverters are an excellent way to maximise the value of your solar PV system by redirecting surplus electricity to heat water instead of exporting it to the grid. When installed and configured correctly, they can significantly reduce energy bills and improve self-consumption of your solar power.
However, like any piece of smart energy equipment, solar diverters can experience issues. At SolarTherm UK, we regularly diagnose and resolve these problems for homeowners and businesses across the South East. Below, we outline the most common solar diverter issues, their causes and how they can be fixed.
The Solar Diverter Is Not Activating
The issue: the diverter fails to send surplus solar energy to the immersion heater, even on sunny days.
Common causes:
- Incorrect CT clamp orientation or placement
- Loose wiring connections
- Incompatible immersion heater or wiring fault
- Export threshold set too high in the diverter settings
How it’s fixed: a qualified engineer will confirm correct CT clamp positioning, verify wiring integrity and ensure the diverter settings match the property’s load profile. In many cases, this is a calibration or configuration issue rather than a faulty unit.
Water Is Not Heating Properly
The issue: the diverter appears to be working, but hot water temperatures are inconsistent or lower than expected.
Common causes:
- Insufficient surplus solar generation
- Scaled or failing immersion heater element
- Competing electrical loads consuming excess power
- Hot water cylinder thermostat issues
How it’s fixed: we assess total household demand, immersion performance and cylinder condition. Sometimes the solution is as simple as replacing a worn immersion element or optimising household load usage during peak solar hours.
Diverter Is Drawing Power from the Grid
The issue: instead of using surplus solar, the diverter is pulling electricity from the grid.
Common causes:
- Incorrect CT clamp configuration
- Software or firmware misconfiguration
- Rapid load changes confusing the control logic
How it’s fixed: this issue requires precise diagnostics. At SolarTherm UK, we fine tune system response times and thresholds to ensure the diverter only activates when genuine surplus power is available.
Error Codes or Warning Lights
The issue: the diverter displays error messages, flashing lights or fault indicators.
Common causes:
- Sensor faults
- Communication errors between components
- Power supply issues
How it’s fixed: each diverter model uses different diagnostics. Our engineers are familiar with all major UK brands and can quickly interpret fault codes, reset systems or replace failed components where necessary.
The System Worked Before but Suddenly Stopped
The issues: the diverter previously functioned correctly but has stopped without any obvious changes.
Common causes:
- Recent electrical work affecting wiring or CT clamps
- Firmware updates or power outages resetting settings
- Component degradation over time
How it’s fixed: a full system health check is performed, including recent changes to the electrical system. We restore correct operation and implement safeguards to prevent recurrence.
Why Professional Diagnosis Matters
Solar diverters operate at the intersection of generation, consumption and export. Small configuration errors can significantly reduce performance or create unnecessary grid consumption. Attempting DIY fixes without specialist knowledge can worsen the problem or invalidate warranties.
At SolarTherm UK we combine in-depth solar PV expertise with manufacturer specific product knowledge. Our solar specialists will ensure your system is fitted to UK electrical standards. At SolarTherm UK we provide practical, cost effective solutions to all your solar needs, from solar PV systems to diverters and EV chargers. Our engineers are fully qualified and have MCS accreditation, ensuring that your system is of high quality and compliant for its lifetime.
Trust SolarTherm UK – The Solar Optimisation Specialists
If your solar diverter is underperforming, behaving unpredictably or not working at all, SolarTherm UK can help. From troubleshooting and repairs to system upgrades and new installations, we ensure your solar investment works as hard as possible for your.
Contact SolarTherm UK today to arrange a professional assessment. If you are looking to start your solar journey or upgrade an existing solar PV system contact us for a free, no obligation quote and design, tailored to your property, usage and future energy needs. No hard sell, just honest, expert advice.
Your home. Your energy. Your future.
