Smart boiler control: the boiler widget

Updated 9 October 2026SmartKnob

The boiler widget makes your water heater smart, whatever the brand and whatever it heats with. You create the widget in the dashboard, and from then on the SmartKnob controls your hot water like a thermostat: to the temperature you want, at the time you want and with several layers of protection. Everything runs directly in the vehicle, without cloud.

Two heating elements, one tile

Many boilers have two heating elements: one for 230V, so shore power or inverter, switched by Switchy, and one for 12V or 24V directly from the battery, switched by Ampy or Switchy. You find both on a single tile and switch them individually.

Boiler widget in the dashboard with water temperature, Auto and Manual, two heating elements and energy today

Controlling to a temperature

In Auto mode you only set the temperature you want, the SmartKnob does the rest. It holds the temperature with short pauses so the heating element does not keep switching on and off.

If you switch by hand while in Auto mode, the tile visibly changes to Manual. There is no hidden automation, you can always see which mode the boiler is in.

Hot water on time

You want to shower at seven? Set the time and the days of the week, just like the alarm on your phone. The SmartKnob works out by itself when it needs to start heating and holds the temperature until your time. A small time reserve is built in, in case your inverter heats a little more slowly.

Hot water timer with days of the week and time

Your battery stays protected the whole time. With shore power or surplus solar power, the boiler always preheats. From the battery only as long as it is above the reserve you have set. If the battery is not enough, the tile shows "Battery too low" instead of simply nothing happening.

You also see live:

  • Time remaining: for example "about 34 minutes until 60°C", calculated from the actual heating speed.
  • Energy today: only what really reaches the water is counted, measured by the current. A faulty heating element counts as zero.

On the detail page you find the temperature history of the last 24 hours, a log of all events, the status of all protection functions and all settings.

Boiler detail page with temperature history, protection status and event log

The automation thinks ahead

  • Preferred heating element with backup: you choose which heating element is preferred, for example the 230V one on shore power. If it is proven that no power is arriving there, the SmartKnob automatically switches to the heating element on the battery. That way you still get hot water. You can switch off this check of the 230V heating element in the settings.
  • Shore power automation: plug in, boiler on. When you plug in, the boiler goes into Auto mode, and when you unplug, it goes back again, each time with a notice. Whatever you have set by hand yourself is never overruled.
  • Other heat sources: if your diesel heater or the engine is already heating the water as well, the electric control pauses by itself. The tile tells you why.
  • Working together with the heating: with heaters that also heat the water, for example Timberline, Truma Combi or water-based heaters from Webasto and Eberspächer, the SmartKnob keeps an eye on things. If the water gets too hot, it first switches off the heating elements, then lowers the target temperature of the heater and only as the last step switches it off completely. Afterwards it restores everything, including your original heater setpoint, even after a restart. If it is cold in the living area at that moment, it skips the gentle lowering, because a bit of boiler optimisation should not cost you a cold night. The emergency shutdown for water that is too hot always applies, though.
  • Frost protection: if the water drops below the limit you have set, between 2 and 10°C, the SmartKnob heats it to a few degrees above. So nothing freezes.
  • Smart Solar Plus (add-on licence): if the battery is full and the sun keeps delivering, the SmartKnob heats the boiler beyond the normal temperature. The boiler becomes a heat store. More on this in Smart Solar Plus: solar surplus becomes hot water.

Hygiene: protection against legionella

At an interval you choose (default: every 7 days), the SmartKnob heats the water to 65°C and holds this temperature for 30 minutes. The sensor checks whether this really worked.

  • The programme prefers to start when there is surplus solar power or shore power is connected, otherwise at the night hour you have set.
  • From the battery it only runs as long as your minimum reserve is not undercut. Otherwise it visibly waits for energy, and it also stops partway through if the battery falls below the reserve.
  • The same reserve applies to the hygiene programme and to the timer. One slider, one rule. Shore power and solar power are exempt, they cost you nothing.
  • Every run is recorded in the log with its date, and the tile shows, for example, "last run 3 days ago".

We only show you what can be verified, that is when the water was last fully heated, and no made-up "legionella probability". The sensor measures the boiler, not the pipes and the shower hose. As background: legionella multiply between 20 and 45°C, and from 60°C they die off quickly.

Protected in several ways

  • Dry-run protection: if the temperature does not rise while heating, the SmartKnob switches off. How long it waits depends on the heating element and the boiler size, for example around 3 minutes at 660W and 10 litres. Only you can switch it back on, never an automation.
  • Faulty heating element: if the heating element is on but no current is flowing, you get a notice after 20 seconds.
  • Overtemperature: above 75°C the boiler switches off and only releases again below 70°C.
  • Fresh water protection: if the fresh water tank is below the minimum, the heating elements stay off. The boiler never heats without water.
  • Battery protection that also works without the SmartKnob: during setup the SmartKnob calculates the fuse value and the undervoltage protection, matched to 12V or 24V and with a reserve for the charging voltage, and stores both in the module. There the protection keeps working on its own, even if the SmartKnob ever fails.
  • Emergency off in the module: if the SmartKnob fails while a heating element is running, the module (Switchy or Ampy) switches the heating element off by itself after a short time. This only applies to heating elements, the fridge and lights stay on. More on this in Heating element protection: your boiler never heats unsupervised.
  • Protection is sent later: if a module could not be reached during setup or was without power for a while, the SmartKnob automatically sends the fuse, undervoltage protection and emergency off as soon as the module is back, and also regularly in the background.
  • Correct time: after a power cut, the timer does not start heating with the wrong time but visibly waits. As soon as you open the dashboard, the clock sets itself automatically. It bridges normal restarts on its own.

Boiler widget with dry-run protection triggered

Honest display

  • If a device cannot be reached, the switch jumps back and the tile tells you. It never shows a heating element as "on" when it is actually off.
  • After a restart it shows "Waiting for data …" instead of a false error message.
  • Every event goes into the log: protection function triggered, mode change, timer, shore power, solar power. So you can always see what happened, when and why.
  • Every piece of information appears exactly once: the tile shows the status, the expanded view the controls and the detail page the history and settings.
  • Run time and switching cycles per heating element, as well as the energy for today, yesterday and in total, are kept even after a restart and a power cut, and so is the log.
  • Protection trips, hygiene runs, interventions in the heating and the highest and lowest water temperature ever measured are recorded in the normal device diagnostics. That way a support request can be answered without anyone on site having to take notes.

Boiler widget settings with control and protection functions

What you need

  • The SmartKnob as the central unit, plus Switchy or Ampy for the heating elements.
  • Fluidy with a temperature sensor on the boiler. You need it for control, timer, time remaining, hygiene programme and frost protection. Without a sensor the widget can only switch, not control.
  • For the fresh water protection, the widget also uses your existing tank widget.

Related questions

How do I connect a new module to the SmartKnob?

Pairing practically takes care of itself. You start it on the SmartKnob or in the dashboard and then power up the module. An LED and a sound on the SmartKnob confirm that the connection is up. That is all there is to it: no cable to the SmartKnob, no configuration, no searching for networks. The only thing that matters is that your SmartKnob is already running, because the modules always connect to it. With Lighty: right after pairing, its wall push buttons stop responding. Create a light widget for each light in the dashboard and switch on "Push button" in it, then they switch again.

Can I use several modules at the same time?

Yes, up to 20 modules at the same time, in any combination. That is enough for almost any camper conversion, from a compact panel van to a fully equipped motorhome. If you want to add several modules one after the other, the SmartKnob stays ready to receive for a short while after each successful pairing. You simply power up the next module.

What is the difference between AP and STA mode?

The two modes only decide which Wi-Fi network you use to open your dashboard on your phone or tablet. They have no effect on your modules. • AP mode: the SmartKnob opens its own Wi-Fi network and you connect your phone or tablet directly to it. You need no router and no internet, ideal when you are parked off-grid. • STA mode: the SmartKnob joins your existing Wi-Fi network, for example your camper router or your phone's hotspot. That is handy if you want internet access at the same time, for instance for online updates. You can switch between the two at any time.

What happens if my Wi-Fi drops out?

You are still never locked out. If the SmartKnob loses the connection to your Wi-Fi network, because the router is off, you have moved to another pitch or you are simply out of range, it automatically opens its own Wi-Fi network again. You can then reach the dashboard directly through it straight away. As soon as your usual network is back, it reconnects to it by itself. You do not have to do a thing.

What happens if the SmartKnob fails?

Ampy and Lighty keep their settings and carry on working. You simply keep switching and dimming lights and appliances at the wall switch, fuses and voltage protection stay active, and the outputs stay as they are. The display, dashboard, scenes, automations, the double tap for all lights and the wireless push buttons pause. This is a fallback, not a permanent state: without the SmartKnob you cannot change settings such as fuse values, and dimming only works with push buttons, not with switches. The one exception: an Ampy output set up as a heating element switches itself off after 10 minutes for safety, so that no boiler keeps heating unattended. We are also working on a backup function where a module takes over the dashboard, so that the whole system can still be operated from your phone and tablet.

What do I need to watch out for when mounting the SmartKnob?

The wall surface under the mounting plate must be flat: no more than 0.5mm of unevenness across the whole area of the mounting plate. If the wall is bent, curved or warped, the SmartKnob will not click in cleanly. Check the surface with a straight edge before screwing the plate on. Double-sided tape on the back of the mounting plate gives extra hold.

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