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Frost monitor
Setting instructions for frost monitors: Protect your greenhouse plants, batteries and much more!
Updated on 30.10.2025
Reader time 2 minutes
How does the frost monitor work?
It automatically recognises frost conditions and switches on the heating to protect your property, plants or appliances - without manual intervention.
What areas or objects can it protect?
It is suitable for a variety of applications including gardens, greenhouses, pipes, driveways, garages and even classic cars. Essentially, it helps prevent frost damage wherever frost could cause problems.
Which models of aktobis electric heaters can be used as frost protection?
Our classic frost monitor is the WDH-BGP02 electric heater frost monitor. However, all our heaters with a heat output of between 2 kW and 3 kW have a thermostat that switches the heater and fan on and off and can therefore be used as frost guards, namely: WDH-BGP03, WDH-BGP031S and WDH-BGP03Pro.
How do I set my electric heater as a frost monitor?.png)
It's quite simple. All these models work according to the same principle:
- Temperature setting (right-hand rotary knob): The temperature should either be set to the minimum value (0 °C) or slightly above. All these heaters have a temperature setting knob with a range corresponding to their heat output. This means that the minimum setting for the BGP02 and BGP03 models is 0 °C and the maximum 45 °C, for the BGP031S model 40 °C and for the BGP03Pro model 85 °C. The centre of the rotary knob corresponds to the centre of the range.
- Heating level (left): Depending on the room size and insulation, heating level 1 or 2 should be selected. For poorly insulated rooms, set your heater to level 2. Just make sure that it is not set to "Fan", as the heating will not work in this setting.
What temperature should I set my frost monitor to in order to protect plants?
To protect your plants from frost, it is best to set your frost monitor to around 5 °C. This provides a safe buffer above the freezing point and ensures that the air and soil remain warm enough even if there is a sudden drop in temperature outside.
Setting the heating to 0 °C is sufficient, but can be risky - by the time the thermostat reacts, the temperature in your greenhouse or garage may already have dropped below freezing, which can damage roots, leaves and sensitive buds.
A constant setting of 5 °C helps to keep sensitive plants such as citrus fruits, geraniums and succulents frost-free without wasting energy. For best results, provide light ventilation to avoid excessive humidity and mould growth.
In short, 5°C is the ideal level to keep plants healthy and protected so they are ready to thrive when spring returns.
What temperature should I set my frost heater to in order to protect my tools and batteries?
Here it is important to differentiate between the risks associated with low temperatures and frost and the risk of condensation leading to corrosion.
- Plants and some objects/materials (liquids, tyres, batteries) must be protected from cold or frost, and
- some other objects (certain tools, vintage cars, etc.) from rust caused by condensation.
The following table summarises some guide values. However, the actual correct setting will depend on the weather conditions, insulation, size, ventilation, etc. When you set up your appliance for the first time, therefore, check the temperature and humidity more often to get a feel for what is best for your rooms.
| Aim | Best practice | Target conditions |
|---|---|---|
| Frost protection (plants) | Frost monitor | 0 to 5 °C |
| Frost protection (e.g. liquids, tyres, seals) | Frost monitor | ≥ 5 °C |
| Prevent loss of performance (e.g. rechargeable batteries) | Indoor storage or frost monitor | 10-12 °C |
| Prevent rust and condensation | Dehumidifier (with slight heat if required) | 45-55 % relative humidity; 8-12 °C |
| Long-term preservation of vintage and classic cars | Dehumidifier & frost monitor | Stable temperature + controlled humidity |
What room sizes are these heaters suitable for?
As a rule of thumb: With simple (not very good) insulation, you can expect 120 watts per square metre. This means that an appliance such as the BGP02 with a maximum heating output of 2.0 kW is sufficient for approx. 16.5 square metres (approx. 41 cubic metres). We use this value in our recommendation.
However, the maximum room size depends primarily on how much cold penetrates (degree of insulation) and how low the temperatures are. With better insulation, the heating output is also sufficient for larger rooms and areas.
