Support

Ohmpilot

Basics

The Fronius Ohmpilot is a load regulator designed to use excess photovoltaic power to heat water.

Thanks to the dynamic variable control from 0 to 9 kW, it is possible to efficiently harness excess PV electricity and use it to power certain electrical loads in the household. The Fronius Ohmpilot is primarily used for the intelligent control of heating rods in boilers and buffer storage tanks. It can also be used for applications such as infrared heaters and towel dryers. In a single-family home with average hot water consumption, it can cover a large proportion of the hot water demand with solar power from April to October.

This results in the household achieving higher self-consumption, lower carbon emissions, and a reduced burden on the existing heating system in the summer months.

More about the product

The Ohmpilot comes with a 2-year Fronius Warranty Plus from the date of dispatch from the Fronius factory. It is not possible to extend the warranty.

Planning & installation

Required system components

Fronius Smart Meter
Fronius GEN24, Verto, or Tauro inverter, or Fronius Datamanager

A Fronius Datamanager Box 2.0 can also be retrofitted in existing photovoltaic systems, regardless of the inverter used. This means that the Ohmpilot can also be used with older Fronius inverters or devices from other manufacturers.

Compatible heating rods

Single-phase from 0.3 to 3 kW
Or three-phase from 0.9 to 9 kW

Only use purely ohmic loads. Heating rods with electronic temperature limiters, fans, or other electronic components are not suitable.

Three-phase heating elements must have a neutral conductor connection at the neutral point and the load must be evenly distributed over all three phases, e.g., 3 × 3 kW.

Heating solutions with more than 9 kW are also possible. These are implemented with a corresponding system configuration, as shown in this circuit diagram.

System functions & integration

The firmware can only be updated via Solar.web. The update is triggered in the Settings area of Solar.web under Components.

The Ohmpilot heats from an excess power of approx. 300 W.

Yes, the Ohmpilot has a control output for engaging a heat pump. The heat pump must in turn have a corresponding control input (for example SG Ready) or a utility-operator release.

When the Legionella prevention function is activated, the water is heated to 60°C at a set interval. The interval can be adjusted on the user interface. It is not possible to set a specific day of the week or a specific time of day.

No, it is not possible to use multiple Ohmpilots in one system.

Help & solutions

1. Press the button on the front of the device twice to activate the WiFi access point. If the blue LED flashes twice repeatedly, the access point is active.

2. Connect your laptop, tablet, or smartphone to the Ohmpilot WiFi network. The network key is 12345678.

3. Enter the IP address 192.168.250.181 in the address bar of your browser to access the user interface.

Pairing with the inverter

When starting for the first time, pairing takes place automatically. However, after a component has been replaced (after maintenance, for example), the inverter and Ohmpilot must be paired again manually. The procedure differs depending on the inverter in question.

Fronius GEN24, Verto, Tauro:

Access the user interface of the inverter. Make sure that the setup wizard has finished running and that setup is complete.
Open the Device configuration menu item and then open Components.
Select Add component, then choose Ohmpilot and add the device.

Fronius SnapINverter (Symo, Primo, Eco):

Access the user interface of the Datamanager. Make sure that the setup wizard has finished running and that setup is complete.
Open the System information menu item.
Under Components, click Pair next to Ohmpilot.

There can be several reasons why excess PV power is being fed into the grid instead of being used for heating.

Troubleshooting: Test boost mode

Press the key on the Ohmpilot three times to activate boost mode.
Boost mode activates control output L1 at 100 percent, while L2 and L3 are switched through. The heating runs at maximum output. Boost mode is deactivated after four hours or by pressing the button again.

Is the device still not heating when in boost mode?

If no heat is being delivered in boost mode, check the following:

Neutral conductor not installed or connected
With three-phase heaters, the neutral conductor must be present and the heating element must be connected in a star connection.
Heating temperature limitation active
Check whether the temperature switch of the heater has tripped. To test this, set the highest possible maximum temperature value and restart boost mode.
Heating element incompatible
Single-phase heating rods from 0.3 to 3 kW and three-phase heating rods from 0.9 to 9 kW are supported. Only use purely ohmic loads. With three-phase heating rods, the load must be evenly distributed over all three phases.

Does the device heat in boost mode, but not in normal operation?

If the system heats in boost mode, but not in normal operation, check the following settings:

Maximum temperature set too low
On the user interface, check under General whether the maximum temperature setting is too low to prevent heating.
No communication with the inverter
Check the data connection between the Ohmpilot and inverter as well as the connection between the components. Modbus RTU via RS485 is recommended for stable communication.

There can be several reasons why electricity is still being drawn from the grid even when sufficient PV power is expected.

Legionella prevention or temperature switch

The heating element temperature switch and an existing temperature sensor detect different temperatures depending on the position.
If Legionella prevention is activated, but the maximum temperature on the heating element is set too low, the required target temperature of 60°C cannot be achieved. In this case, the Ohmpilot tries to achieve the target temperature at intervals of several hours, which can lead to electricity being drawn from the grid.
To avoid this behavior, increase the maximum temperature at the heating element temperature switch.

Minimum temperature setting

Check the setting of the day curve on the user interface under General.
If a minimum temperature is specified for a longer period of time, the system will attempt to maintain this constant temperature. This can also lead to electricity being drawn from the grid.

Incorrect Smart Meter readings

The heating output is set on the basis of the measured values from the Fronius Smart Meter. If the Smart Meter delivers incorrect or implausible values (for example due to incorrect installation), the regulator cannot operate correctly.
In Solar.web, check whether the values for grid feed-in and grid consumption are plausible and continuously available.