Product Overview & Areas of Application
The fothermo PVB-30 is a wall-mounted solar off-grid boiler for direct hot water preparation using direct current from photovoltaic modules. In pure PV operation, the storage tank does not require a connection to the public 230 V power grid, making it suitable for garden houses, holiday homes, and other off-grid applications.
The device belongs to the 30-liter class and has an actual usable capacity of 29 liters. In addition to providing an independent hot water supply, the off-grid boiler can be used for preheating drinking water before a tankless water heater or an existing heating system.
Technology & Equipment
The integrated heating element uses up to 550 W depending on the available solar power. An MPP tracker adapts operation to the operating point of the connected photovoltaic modules. The current water temperature, PV power, PV voltage, and the total photovoltaic energy used can be viewed on the digital display.
The pressure-resistant steel tank is enameled on the inside and additionally protected against corrosion by a magnesium anode. Thermal insulation made of CFC-free polyurethane foam reduces heat losses. The PVB-30 achieves energy efficiency class A+.
Everyday Benefits
By directly using photovoltaic power, water is heated without an upstream inverter. A connected PV power of 300 to 600 Wp is recommended for the PVB-30. A larger generator output can help maintain the available heating power for longer, especially in weaker sunlight.
At maximum heating power, the water temperature in the 30-liter model rises by approximately 16 °C per hour. The actual temperature increase depends, among other things, on the initial temperature, water draw-off, ambient temperature, and current solar radiation.
System Integration & Compatibility
The photovoltaic modules are connected via MC4 connectors and may only be wired in parallel. The maximum open-circuit voltage is 42.4 V DC. Depending on the module type used, up to five modules with a total maximum of 1,500 Wp can be connected.
Using separately available fothermo components, the off-grid boiler can also be operated with a power supply unit, a suitable 12 V or 24 V battery system, or an external energy management system. The required connection cables and power supply devices are not included in the standard scope of delivery.
Technical data at a glance
| Storage type | Photovoltaic 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 polyurethane foam |
| Maximum water temperature | 65 °C |
| Nominal pressure | 7 bar |
| Dimensions | Height 600 mm, width 400 mm, depth 400 mm |
| Weight | 15 kg |
Mounting
The PVB-30 is intended exclusively for vertical, fixed wall mounting in a dry and frost-free room. The mounting must be designed to support at least three times the weight of the appliance when filled with water. Sufficient space must be provided below the tank for the water and photovoltaic connections.
The combined check and pressure relief valve is mounted on the cold water connection. The supply pressure should be between 1 and 5 bar. If the line pressure is higher, an additional suitable pressure reducing valve is required. Before connecting an electrical energy source, the tank must be completely filled with water.
Notes
Photovoltaic modules may only be connected in parallel. A series connection can damage the tank. The maximum open-circuit voltage and the permissible connection power must be observed when selecting the modules.
During water heating, expansion water may escape from the pressure relief valve. The valve opening must not be sealed. The magnesium anode must be checked regularly and replaced by a qualified professional if necessary. In regions with hard water, regular inspection and descaling are required.
Scope of delivery
- 1 x fothermo solar off-grid boiler PVB-30
- 1 x combined check and pressure relief valve
- 1 x manufacturer's operating instructions
