Product Overview & Areas of Application
The fothermo PVB-80 is a wall-mounted solar off-grid boiler for direct hot water preparation using direct current from photovoltaic modules. In pure photovoltaic operation, the storage tank requires neither an inverter nor a connection to the public 230 V power grid.
The device belongs to the 80-liter class and has an actual usable capacity of 77 liters. It is suitable for independent hot water supply at off-grid locations as well as for preheating drinking water before an electric instantaneous water heater or an existing heating system.
Technology & Equipment
The integrated heating element uses a heating output of up to 550 W, depending on the available solar energy. An MPP tracker adapts the electrical operating point to the connected photovoltaic modules and the current solar radiation.
The digital display shows the current water temperature, the input power and input voltage of the photovoltaic modules, as well as the total photovoltaic energy used. An integrated reverse polarity protection supports safe PV connection.
The pressure-resistant storage tank is made of steel with an enamel coating and is additionally protected against corrosion by a magnesium anode. A 33 mm thick insulation made of polyurethane foam reduces heat losses from the storage tank.
Everyday Benefits
For the PVB-80, a photovoltaic output of 600 to 1,200 Wp is recommended. A higher connected module output supports hot water preparation, especially in weaker sunlight. According to the current product data sheet, up to 2,000 Wp can be connected, while the electrical heating output of the boiler remains limited to a maximum of 550 W.
With a heating output of 550 W, the water temperature increases by approximately 6 °C per hour. When the storage tank is fully heated to 65 °C, depending on the cold water temperature, about 180 liters of mixed water at 34 °C can be provided.
System Integration & Compatibility
The photovoltaic modules are connected directly to the off-grid boiler via MC4 connectors. Multiple modules may only be connected in parallel. The maximum open-circuit voltage of the connected modules must be limited to 42.4 V DC.
For optional auxiliary heating, an approved fothermo power supply unit can be connected. Depending on the power supply unit used, auxiliary heating outputs of 60, 160, or 240 W are available. The power supply unit, photovoltaic modules, parallel connectors, and extension cables are not included in the standard scope of delivery.
Technical Data at a Glance
| Storage Type | Photovoltaic Electric Wall-Mounted Storage Tank |
| Usable Capacity | 77 liters |
| Suitable for Drinking Water | Yes |
| Storage tank | Steel with enamel coating |
| Heat exchanger | None |
| Insulation | 33 mm rigid polyurethane foam |
| Maximum water temperature | 65 °C |
| Maximum operating pressure | 7 bar |
| Dimensions | Height 900 mm, width 480 mm, depth 470 mm |
| Weight | 25 kg |
Mounting
The PVB-80 is intended exclusively for vertical, fixed wall mounting in a dry and frost-free room. The mounting elements and the load-bearing wall must be designed for at least three times the weight of the storage tank when filled with water.
The combined check and pressure relief valve must be installed at the cold water connection. The water pressure should be between 1 and 5 bar. If the supply pressure is higher, a suitable pressure reducing valve is required.
Before connecting the photovoltaic modules or another approved energy supply, the storage tank must be completely filled with water and the hydraulic installation must be checked for leaks.
Notes
Photovoltaic modules may only be connected in parallel. A series connection can exceed the permissible input voltage and damage the off-grid boiler.
During water heating, expansion water may escape from the pressure relief valve. The side valve opening must remain permanently open and the escaping water must be safely drained via a suitable drain option.
The magnesium anode is a wear part and must be checked regularly by a qualified technician. In regions with hard water, regular inspection and cleaning of the storage tank is also required.
Scope of delivery
- 1 x fothermo solar off-grid boiler PVB-80
- 1 x combined check and pressure relief valve
- 1 x manufacturer's operating instructions
