Product Overview & Areas of Application
The fothermo PVB-30-AC is a wall-mounted solar hybrid boiler for water heating using photovoltaic power and on-demand auxiliary heating via the 230 V mains supply. The direct current from the connected photovoltaic modules is used directly to heat the stored water without an upstream inverter.
The device belongs to the 30-liter class and has an actual usable capacity of 29 liters. Thanks to the integrated mains auxiliary heating, the hybrid boiler can replace a classic electric boiler in a compact hot water system and maintain an adjustable minimum temperature even when solar radiation is low.
Technology & Equipment
For photovoltaic operation, a continuously adjustable heating output of up to 550 W is available. An integrated MPP tracker adjusts the operating point to the available solar power. The digital display shows the water temperature, PV input power, PV voltage, and the total photovoltaic energy used.
A second heating element enables auxiliary heating with 1,500 W via the 230 V mains supply. The desired minimum temperature is set using a rotary thermostat. If the water temperature falls below this value, the water is automatically reheated with mains electricity.
The pressure-resistant storage tank is made of enamelled steel and is additionally protected against corrosion by a magnesium anode. Thermal insulation made of CFC-free polyurethane foam reduces standby heat losses.
Everyday Benefits
Water heating is primarily carried out with directly available solar power. The mains auxiliary heating only takes over when the set minimum temperature is not reached. This reduces the share of mains electricity without having to completely do without weather-independent hot water supply.
At maximum PV heating output, the water temperature increases by approximately 16 °C per hour. The 1,500 W mains auxiliary heating achieves a temperature rise of about 43 °C per hour. A storage tank fully heated to 65 °C can provide approximately 72 to 75 liters of hot water at around 34 to 35 °C when mixed with cold water.
System Integration & Compatibility
The photovoltaic modules are connected directly to the hybrid boiler via MC4 connectors. Multiple modules must only be connected in parallel. For the 30-liter model, a photovoltaic output of 300 to 600 Wp is recommended; up to 2,000 Wp can be connected. The maximum open-circuit voltage must not exceed 42.4 V DC.
The hybrid boiler can also be operated exclusively with photovoltaic power. For automatic grid-based auxiliary heating, the existing 230 V connection is connected to a suitable socket. Photovoltaic modules, parallel connectors, extension cables, and mounting systems must be selected separately.
Technical Data at a Glance
| Storage Type | Pressure-resistant solar electric wall-mounted storage tank |
| Usable Capacity | 29 liters |
| Suitable for drinking water | Yes |
| Storage tank | Steel with enamel coating |
| Heat exchanger | None |
| Insulation | CFC-free rigid polyurethane foam |
| Maximum water temperature | 65 °C |
| Maximum operating pressure | 7 bar |
| Dimensions | Height 600 mm, width 400 mm, depth 400 mm |
| Weight | 15 kg |
Mounting
The PVB-30-AC is intended exclusively for vertical, fixed wall mounting in a dry and frost-free room. The wall and mounting elements must be designed for at least three times the weight of the device when filled with water.
The combined check and pressure relief valve must be installed at the cold water connection. The supply pressure should be between 1 and 5 bar. If the line pressure is higher, a suitable pressure reducing valve is required.
Before connecting the photovoltaic modules or the 230 V mains supply, the tank must be completely filled with water, vented, and checked for leaks.
Notes
Photovoltaic modules may only be connected in parallel. A series connection can exceed the permissible input voltage and damage the hybrid boiler.
During water heating, expansion water may escape from the pressure relief valve. The side valve opening must remain permanently open and be drained via a suitable drain option.
The magnesium anode is a wear part and must be checked regularly. In addition, if the water is hard, the storage tank must be checked and descaled on a regular basis.
Scope of delivery
- 1 x fothermo solar hybrid boiler PVB-30-AC
- 1 x combined check and pressure relief valve
- 1 x manufacturer's operating instructions
