Product Overview & Application
The fothermo PVB-80-AC is a wall-mounted solar hybrid boiler for domestic hot water preparation with directly connected photovoltaic modules and demand-based reheating via the 230 V mains supply. The direct current from the PV modules is converted into heat directly in the storage tank without an upstream inverter.
The device belongs to the 80-liter class and has an actual usable capacity of 77 liters. Thanks to the integrated mains reheating, the hybrid boiler can replace a conventional electric boiler and maintain an adjustable minimum temperature even when solar radiation is low.
Technology & Equipment
For photovoltaic operation, a heating output of up to 550 W is available. An integrated MPP tracker adjusts the electrical operating point to the available solar power. The current water temperature, PV input power, input voltage, and total photovoltaic energy used can be read on the digital display.
A second heating element enables reheating 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 using mains electricity.
The pressure-resistant storage tank is made of enamelled steel and is additionally protected against corrosion by a magnesium anode. The thermal insulation made of CFC-free polyurethane foam reduces standby heat losses. The PVB-80-AC has energy efficiency class C, load profile M, and a sound power level of 15 dB.
Everyday Benefits
Hot water preparation is primarily carried out using directly available photovoltaic energy. The mains reheating only takes over when the minimum temperature set on the thermostat is not reached. This allows the proportion of mains electricity to be reduced without having to do without weather-independent hot water supply.
At maximum PV heating output, the water temperature increases by approximately 6 °C per hour. The 1,500 W mains reheating achieves a temperature rise of about 16 °C per hour. If the storage tank is fully heated to 65 °C, approximately 180 liters of hot water at around 34 °C can be provided when mixed with cold water.
System Integration & Compatibility
The photovoltaic modules are connected directly to the hybrid boiler via MC4 connectors. Multiple modules may only be connected in parallel. For the 80-liter model, a photovoltaic output of 600 to 1,200 Wp is recommended. In total, up to 2,000 Wp can be connected, while the heating output of the boiler remains limited to a maximum of 550 W.
The maximum open-circuit voltage of the connected modules must not exceed 42.4 V DC. For automatic grid-assisted reheating, the existing 230 V connection is connected to a suitable socket. Photovoltaic modules, parallel connectors, extension cables, and mounting systems are not included in the standard scope of delivery.
Technical Data at a Glance
| Storage Type | Pressure-resistant solar electric wall-mounted storage tank |
| Usable Capacity | 77 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 |
| Energy efficiency | Class C, load profile M |
| Dimensions | Height 900 mm, width 480 mm, depth 470 mm |
| Weight | 25 kg |
Installation
The PVB-80-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 appliance 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 must 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, with hard water, regular inspection and descaling of the storage tank are required.
Scope of delivery
- 1 x fothermo solar hybrid boiler PVB-80-AC
- 1 x combined check and pressure relief valve
- 1 x manufacturer's operating instructions
