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Switch off an appliance left running

Switch off an appliance left running

How it works

A Shelly 1PM Gen4 sits behind the heater's power point, or in a hardwired heater's supply, and switches it. Its Auto off timer switches the heater off a set time after it comes on, and the setting is stored on the relay, so it works whether the heater was turned on from the app, a home app or the wall switch.

The 1PM also measures what the heater draws. That gives you a power limit that cuts it off above a wattage you choose, and, if you want one, a phone alert when the heater has been drawing power for longer than you'd expect.

  1. Shelly app timer screen for a device named Heater, with auto off set to two hours. 01

    Your phone

    Turn the heater on from the app, or get a message when it's been running too long.

  2. 1PM Gen4 Smart Relay 02

    Shelly relay

    Switches the heater off once the timer runs out, however it was turned on.

  3. 03

    Your heater

    Plugs in or is wired in as it is now.

Check your heater first

Check the rating on the heater's label before you pick a relay. The Shelly 1PM Gen4 switches up to 16 A, enough for a 2,400 W heater.

  • Up to 16 A
  • Up to 2,400 W

What it looks like on your phone

  • Two hours, then off. Auto off switches the heater off two hours after it comes on, whoever turned it on.

  • A ceiling on the draw. Max power protection turns the heater off if it ever pulls more than 2,600 W.

  • See when it ran. The activity log lists every time the heater turned on and off.

Step by step

How you'll set it up

Add the device to Wi-Fi from your phone, or straight from a browser.

Download Shelly Smart Control on the App Store Get Shelly Smart Control on Google Play

  1. Fit the Shelly to the heater's supply

    Mains goes to L and N. O feeds the heater, or the power point it plugs into, and the neutral runs back as before. A wall switch, if there is one, goes to SW so it still works.

    Wire map 1PM Gen4
    • Active (supply) L
    • Neutral N
    • Appliance O
    • Wall switch (optional) SW
    Circuit overview
    LN230 V~ 50 Hz1Appliance2Wall switchOSWLLLNNShelly 1PM Gen4
    1Appliance2Wall switch
    Active (supply)Neutral / 0 VSwitched loadSwitch signal / dry contact

    In Australia, fixed 230 V wiring is licensed-electrician work. Use these diagrams to plan the job and brief your electrician.

    Showing the whole circuit

    Shelly 1PM Gen4

    100%
    LN230 V~ 50 Hz1Appliance2Wall switchOSWLLLNNShelly 1PM Gen4
    1Appliance2Wall switch

    Select a terminal to follow its wiring.

  2. Add it to the Shelly app and name it Heater

    Add the relay in the Shelly Smart Control app and name it Heater, so the timer, the limit and any alert all say what they're for.

    Learn how to add a device to the Shelly app

  3. Turn on auto off

    In the app, open Timer, tick Auto off, set it to 02:00:00 and tap Save. In the web interface, open the output, then Timers: tick Enable under Auto OFF, enter 7200 seconds and click Save. From now on the heater switches itself off two hours after it comes on.

  4. Set a power limit

    In the app, open Safety and expand Max power protection. In the web interface, it's Overpower in watts under Protections. Enter a figure a little above the wattage on the heater's label (2600 for a 2,400 W heater) and tap Save, or click Save in the web interface. If the heater ever draws more, the relay turns it off.

  5. Check the countdown

    Turn the heater on. The main screen shows a countdown beside the power reading, starting from 02:00:00, and the heater switches itself off when it reaches zero.

  6. Add it to your home app over Matter

    Matter is on by default on the Gen4, so scan the QR code on the device label with Apple Home, Google Home or SmartThings.

Optional: get a message when it's still running

Auto off looks after the heater on its own. If you'd also like to know, a scene in the Shelly app sends your phone a notification when the heater has drawn more than 500 W for an hour.

  1. Watch the heater's power

    In the Shelly app, open the heater's room, go to Scenes and tap +. Tap Add condition, then Create condition, choose Device based and pick Heater. Choose Power Consumption, enter 500 and tap More than 500 W.

  2. Trigger it once, after an hour

    Choose Trigger, turn on Trigger custom settings, pick Once and set Condition is valid to 60 minutes, then tap Save.

  3. Send it to your phone

    Tap Next, then Add action, Create action and Notify action. Choose Phone notification, then follow the last screens to save the scene.

  • The rule on one card. The heater drawing more than 500 W for 60 minutes sets it off, once.

  • Straight to your phone. Phone notification sends the alert through the Shelly Smart Control app.

Frequently asked questions

Should I use the Shelly app or Home Assistant?

If you don't run Home Assistant, use the Shelly app: it needs no hub, and Auto off and the power limit are stored on the relay. If Home Assistant already runs your home, put the heater there, so it sits alongside your other automations and its power history.

What happens when it switches off?

The heater stops until someone turns it back on, from the Shelly app, a home app or the wall switch if it's wired to the relay. The two hours start again each time it comes on.

Will it work with my heater?

Check the rating on the heater's label: the 1PM Gen4 switches up to 16 A and the 1PM Mini Gen4 up to 8 A. For a plug-in heater, the relay goes behind the power point it plugs into; a hardwired heater has the relay in its supply.

Can it tell me when the washing machine has finished?

Yes, with a relay on the washing machine's power point. Build the same scene with Less than instead of More than, at a few watts and valid for 10 minutes, so a pause mid-cycle doesn't set it off. Leave auto off turned off on that relay.

Can it warn me if the freezer stops?

It can tell you when the freezer stops drawing power, with a Less than scene over a longer window, since a freezer rests between cycles. Never turn on auto off for a freezer's relay.

What if the internet drops out?

Auto off and the power limit are stored on the relay itself, so they keep working on your local network. The phone alert comes through the Shelly app, so it needs the internet.

Can I see how much power it uses?

Yes. The 1PM measures the heater's power draw, shown live in watts on the main screen with a chart of the last 24 hours.

Does it still switch off if Home Assistant is down?

Not on the two-hour timer: that automation runs in Home Assistant. The power limit is stored on the relay, so it keeps working. If you want the timer on the relay as well, set Auto off in the Shelly app too.

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