2350W solar system with a 120L Nexol water heater for hot water production

The configurable PV hot water kit from Offgridtec (MPN: 025255) combines the Nexol NEX RS 120 hybrid solar water heater with three to five Trina Solar 470 W modules. Depending on the selected configuration, this provides a module output of 1,410 to 2,350 Wp. The DC power generated is used to heat water without the need for a separate inverter. If necessary, the 120-liter storage tank can be reheated via a 230 V mains connection. The system is intended for permanent installation by qualified professionals.

The Advantages of the PV Hot Water Kit

• Configurable PV output with N-type i-TOPCon double-glass modules, each rated at 470 Wp
• 120-liter pressurized storage tank with integrated MPP tracking and up to 1.5 kW of PV heating capacity
• Direct PV water heating without a separate inverter
• Optional supplementary heating via a 230-V mains connection
• Includes 23 to 25 m of H1Z2Z2-K solar cable and two PV Stick sets

The system consists of:

• 1x Nexol NEX RS 120 Hybrid Solar Water Heater 120L 1.5kW
• Trina Solar 470W Vertex S+ double-glass N-type i-TopCon solar module (3–5 units, depending on selection)
• H1Z2Z2-K 1X6 WH/BK single-conductor solar cable, EN50618 IEC60228 (23–25 m, depending on selection)
• 2x Weidmüller PV-Stick Set

Important Note: The 5-module configuration is intended only for locations where the minimum module temperature does not fall below −15 °C. For colder locations, such as parts of Scandinavia or alpine regions, select the 3- or 4-module configuration.

PV Power Directly for Hot Water Production

The boiler feeds the direct current from the connected module string to the heating system via an integrated MPP tracker. No additional inverter is required for this. The boiler’s maximum usable PV power is 1.5 kW. Excess module power does not increase the heating output beyond this value but can provide the system with more available PV power when solar irradiance is low. For periods when PV output is insufficient, an electric backup heater operating at 230 V is available. The operating mode and hot water temperature can be set via the touchscreen display.

Three Selectable Module Configurations

The modules are connected in series as a single string. Depending on the selection, 1,410 Wp with three modules, 1,880 Wp with four modules, or 2,350 Wp with five modules are available. The maximum open-circuit voltage of the Nexol PV input is 300 V. Since the module voltage increases at low temperatures, the 5-module variant must be verified by a qualified contractor based on the lowest design temperature at the installation site. The permissible input voltage must not be exceeded under any operating conditions.

NEX RS Hybrid Solar Water Heater

The NEXOL water heater combines state-of-the-art solar technology with efficient water heating and reliably provides hot drinking and domestic water. It uses solar power from the connected photovoltaic modules and, if necessary, can provide additional heating via the 230V power grid—each with a heating output of 1,500 W. Thanks to the built-in Nexol heating element, you have all these benefits right in your water heater.

• Easy to use: Touchscreen control
• Energy self-sufficient: PV power takes priority
• Easy installation—no permit required

470 W Trina Solar Vertex S+ double-glass modules

Thanks to modern technologies such as high-density cell interconnection, the spacing between solar cells is minimized, allowing more sunlight to be harnessed. Multi-busbar and N-type i-TOPCon technology further ensure higher light conversion efficiency, fewer energy losses, and better current conduction. With an efficiency of 23.5%, the module reliably delivers energy even on cloudy days or during periods of shade. The sturdy double-glass construction provides optimal protection for the panel against the elements and fire.

• High-Density Cell Interconnection Technology
• Double-glass for optimal reliability
• Low series resistance, improved current conduction
• Excellent resistance to fire and environmental influences
• 5,400 Pa shear load and 4,000 Pa wind load (test loads)
• High compatibility with inverters

Technical Specifications

Nexol NEX RS 120

• Nominal capacity: 120 l
• Maximum usable PV power: 1.5 kW
• Maximum DC heating power: 1.5 kW
• Maximum AC heating power: 1.5 kW
• Minimum PV nominal voltage: 100 V
• Maximum PV open-circuit voltage: 300 V
• Maximum PV short-circuit current: 15 A
• PV connections: MC4
• MPP tracking: integrated
• Mains connection: 230 V, 50–60 Hz
• Adjustable temperature: up to 65 °C
• Protection rating: IP24
• Operating weight with water: approx. 148 kg
• Dimensions: 1110 × 440 × 440 mm

Trina Solar Vertex S+ 470 W

• Rated power per module: 470 Wp
• MPP voltage: 46.1 V
• MPP current: 10.20 A
• Open-circuit voltage: 54.6 V
• Short-circuit current: 10.89 A
• Module efficiency: 23.5%
• Junction box protection rating: IP68
• Weight: 21 kg per module
• Dimensions: 1762 × 1134 × 30 mm

Notes on Installation and Commissioning

Water connection, PV cabling, ground connection, grid connection, and commissioning must only be performed by appropriately qualified professionals. The water heater is intended for permanent indoor installation. When mounting on a wall, the operating weight of approximately 148 kg must be taken into account. The necessary hydraulic safety devices must be provided for the pressure-resistant hot water storage tank. The mounting system, DC disconnect switch, safety assembly, and other site-specific installation materials are not included in the set.