Mill Heaters & Smart Devices: Frequently Asked Questions (FAQ)

Last updated: October 2, 2026. Source: Mill Norway official help center.

Table of contents

1. General Q&A
2. Panel Heaters
3. Smart Plug
4. Wi-Fi Socket
5. Floor Convection Heaters
6. Oil Heaters
7. Mill Sense (Air Quality Sensor)
8. Mill Air Purifiers (Silent Pro)
9. Outdoor / Patio Heaters
10. Matter, API & Homey Integration

General Q&A

Connectivity & setup

How do I contact Mill customer service?

Mill Customer Service can be reached through the chat bubble in the Help Center or directly in the Mill Norway app: go to Settings → Contact us → Ask us a question. Mill does not offer phone support.

How do I connect a Generation 3 device?

Before connecting a Generation 3 device: reset it first if it was previously connected, enable Bluetooth and location services on your phone, disable “Smart Wi-Fi”/band-steering on your router, and connect using a pure 2.4 GHz network or a combined 2.4/5 GHz network — a pure 5 GHz network will not work. A work phone with strict security policies can also block pairing; use a personal phone if needed.

To pair: tap the “+” icon on the app’s home screen → New device → select your product → select the correct generation → follow the in-app instructions. A reset walkthrough video is available at Mill’s YouTube channel. If connection still fails, contact support with a photo of the product label.

How do I connect a Generation 2 heater?

If a Generation 2 device has gone offline, turn it off and on again to trigger automatic reconnection; if that fails, move it closer to the router and retry.

For a clean setup, create a guest Wi-Fi network with: 2.4 GHz only, mode g/g-n (not AC/AX), channel 1 or 6, 20/40 MHz bandwidth, WPA2 with AES, DHCP enabled, and WMM/APSD/power-saving, airtime fairness, smart beam and VPN all disabled. Open ports 1883 (MQTT) and 80 (HTTP) on your firewall. Connect your phone to this network before setup, then use “+” → New device → select product → select generation → follow instructions. An “alternative Wi-Fi connection” option is also available in-app (not supported on oil heaters).

Where can I find the model number / serial number of my device?

Every Mill device has a sticker with the model and serial number:

• Sockets: back of the device
• Panel heaters: right side, under the ON/OFF switch (two stickers)
• Floor heaters and oil heaters: underside, near where the power cord exits (two stickers)
• Mill Sense: underside of the device
• Mill Silent Pro air purifiers: underside of the device
• Outdoor heaters: back of the device

Which generation of Mill device do I have?

Check the Wi-Fi serial number printed on the device — the prefix identifies the generation and production year:

I changed my home network. How do I reconnect my devices?

Reset each device and reconnect it as new — search the help center for your specific product to find its reset method, then follow the standard “+” → New device pairing flow.

How do I calibrate a device?

Via the Mill Norway app (Socket, Smart Plug, panel heaters, floor heaters, oil heaters): place a separate thermometer centrally in the room (or on a wall at chest/shoulder height) for 24 hours, then go to Settings → Calibration → select device and enter that sensor’s reading.

Directly on a Gen3 heater: press the gear button twice, use the arrows to enter the actual room temperature, and confirm with the gear button (or wait 5 seconds).

Directly on a Gen3M / Gen4 heater: press the gear button to open the menu, navigate with +/- to “CAL”, press gear to enter calibration mode, adjust with +/- to the actual temperature, and confirm (or wait 10 seconds).

Heaters with a mechanical (non-digital) thermostat cannot be calibrated.

Can I transfer my devices to a new owner?

No — device transfer between Mill accounts isn’t supported, both for GDPR reasons and because a change of ownership usually also means a new Wi-Fi network, which requires the devices to be reset and re-added anyway.

How many Mill devices can I run on one network?

There’s no fixed limit from Mill — it depends on your router and ISP’s capacity. Mill devices use very little bandwidth, so this is rarely an issue unless you have an unusually large number of devices on a weak router.

Using the Mill app

How do I change my password in the Mill Norway app?

Go to Settings → Account Details → Password, enter your current password, enter the new password twice, and tap Save changes.

I don’t remember my password. What do I do?

In the app, select “Forgot my password”. You’ll receive a PIN code by email (check your spam folder if it doesn’t arrive), enter the PIN, and set a new password.

How do I create a weekly program?

Open the app → Programs tab → tap “+” → name the program and confirm → tap the program to edit its times and modes. To delete a program, use the three-dot menu next to its name and select Delete.

What is “override”?

Override lets you set a fixed temperature instantly, pausing your scheduled program. It can run continuously or for a set timer duration, and can be applied to your whole home or to individual rooms — accessible from the main screen or a room’s own settings.

How does the statistics feature work?

The app logs temperature, power consumption, humidity, and air quality (depending on your products) — but these update only once per hour, not in real time, so it can take a little while before data appears for a newly connected device.

How do I share my house with other people?

Go to Settings → House → select your home → Invite, then enter the other person’s email address. You can restrict them to specific rooms only. If a shared user can’t see the home, make sure both apps are updated; if access still breaks, remove the user and re-share. To remove access: Settings → House → select home → tap the member → Remove.

Can multiple people control the same Wi-Fi devices?

Yes, via the household-sharing feature above — the account owner controls who has access and to which rooms.

Heater performance & troubleshooting

Do different Mill heater models use power more efficiently than others?

No — all Mill heaters are equally efficient. 100 watts of power consumption produces 100 watts of heat, whether it’s a panel heater, a free-standing convection heater, or an oil radiator.

Should I choose an oil heater, a floor heater, or a panel heater?

Panel heaters and Wi-Fi floor heaters use an aluminium heating element that heats up fast and stays at a lower surface temperature; dust and hair melt rather than burn on it, so these are not considered a fire hazard. Floor heaters without Wi-Fi use a heating wire that does burn dust and hair — don’t leave these unsupervised, and turn them off before bed. Oil-filled radiators heat up more slowly but don’t dry out the air as much, which helps air quality, and they retain heat longer after being switched off.

All three technologies convert 100% of the electricity they use into heat — pick based on how fast you need the room to heat up, how it affects air humidity, and whether it needs to run unsupervised.

What is the day-/night function?

On Mill oil and panel heaters (non-Wi-Fi models with “DN” in the name), the day/night function automatically lowers the temperature at night or while you’re away at work. Setup steps are in the product’s user manual (downloadable from Mill’s support pages).

The heater’s power cord is too short — can it be extended?

Most models ship with a 1.3 m cord (0.8 m on 250W panel heaters). It’s legal to extend the cord up to a total of 1.9 m, or you can move the power outlet instead. Any cord extension must be done — and documented — by a qualified electrician.

There’s something loose/rattling inside the heater — is that normal?

Yes. All Mill floor and oil heaters have a tip-over safety switch that uses a small ball rolling inside a cage; you’ll hear it move when the heater is moved or tilted. This is normal and not a fault.

My heater is heating too much or too little relative to the set temperature. What do I do?

The thermostat should be accurate to within ±0.2°C, but draughts or heater placement can cause a mismatch with the room’s felt temperature. Most heaters with a digital display can be calibrated (see How do I calibrate a device? above) via the user manual or the Mill app. Heaters with a mechanical thermostat, or built before 2017, cannot be calibrated.

My heater doesn’t heat. What do I do?

Check that the lightning-bolt symbol is lit — it should be whenever the heater is actively heating. If it’s lit but there’s still no heat, reset the heater:

• Gen2: Turn the heater off, then hold the gear button while turning it back on; it will settle at 22°C once reset.
• Gen3: Turn off, then turn on and immediately hold the gear button until the display cycles through “CHL” → “COL” → “FR” — release on “FR”. It will count up and settle at 22°C.
• Gen3M: Press the gear button, navigate with +/- to “Hr”, press gear to enter reset mode, select “YES” with +/-, confirm with gear. “YES” blinks, the heater restarts, and settles at 22°C.

After resetting, you can set the temperature up to 35°C.

My heater makes noise. What do I do?

A clicking sound when heat turns on/off is normal, and oil heaters may crackle as the oil moves. Knocking or banging usually comes from the aluminium heating element expanding/contracting on its internal mounting track as it heats and cools — this isn’t dangerous, though it can be annoying. If it bothers you, check whether the unit is still under warranty and contact your retailer.

What happens if I tip the heater over?

Free-standing models have a tip-over safety switch: a small metal ball sits in a cage, and if the ball isn’t resting at the bottom (i.e., the heater isn’t upright), power to the heating element cuts off. The heater must be standing upright on the floor to produce heat.

What happens if the power goes out?

The heater remembers its last temperature setting through a power cut. Once power returns, it reconnects to Wi-Fi automatically and picks up any schedule or command changes made in the meantime.

How much heater wattage do I need?

Mill recommends roughly 70–100 W per square metre, depending on insulation. In larger rooms, several smaller heaters are often better than one large one, as long as the combined wattage is sufficient. Higher wattage heats the room faster and reaches a higher maximum temperature in very cold weather.

The lights in my house flicker when the heater turns on. Why?

This is caused by the heater’s PID temperature control rapidly switching power on and off. Fix it by enabling “Slow PID” in the Mill app: select the heater → scroll down → turn on Slow PID. This smooths out the heater’s power draw so it doesn’t destabilize the circuit.

Frost protection — what’s the lowest temperature I can set?

5°C is the lowest available setting, giving a safety margin against frost, since Mill devices are not designed to operate below 0°C.

What is the highest/lowest temperature I can set?

5°C minimum, 35°C maximum.

What is PID control?

PID control lets the heater run below full power while keeping the room temperature stable, by switching the heating element on and off rapidly — e.g., if it’s off 50% of the time, you get roughly half the heat output.

Display codes & symbols

The display shows “CH” or “CHL” and won’t respond. What does that mean?

CH/CHL means child lock is active, preventing accidental changes.

• Gen3: Turn the heater off, then on; within 5 seconds, hold the gear button until “CH/CHL” appears, then release to toggle it.
• Gen3M/Gen4: Open the menu with the gear button, navigate to “CHL”, press gear to lock (blinks twice); to unlock, quickly press the gear button 5 times.
• In the app: open the heater, scroll to Child Lock, and toggle it (green = on, grey = off).

“FO” shows in the display. What does it mean?

FO means the open-window function has triggered — it activates automatically if the room temperature drops more than 5°C within 15 minutes, and the heater stops heating (dropping to 5°C above freezing, to prevent frost damage) until the temperature rises 3°C within 15 minutes, or for a maximum of 1 hour.

• Gen3: press the function button once to exit; hold it 3 seconds to turn the feature on/off (also controllable via the app).
• Gen3M/Gen4: open the menu, navigate to “Fo”, choose On/Off, and confirm (also controllable via the app).

The display on my Gen3 heater shows “OFF”. What does that mean?

The heater has been switched to Off mode in the app and won’t heat regardless of room temperature. Open the app and change the mode, or turn the heater back on, to resume normal operation.

“CO” or “COL” appears on the display. What does that mean?

CO/COL means Commercial Lock is active, blocking all temperature changes.

• Standard Gen3 heaters, Gen3 floor heaters, CO1500MAX: turn the heater off, then on; within 5 seconds hold the gear button ~10 seconds until the display cycles “CHL” → “COL”, then release.
• Gen3M/Gen4: activation is app-only. To deactivate on the unit: press gear twice until “000” shows, use +/- to change it to “123”, confirming each digit, then confirm again — COL blinks and unlocks. (Deactivation also works via the app.)

What does “FAL” mean on the display?

FAL means fall protection has triggered — the heater has detected it isn’t standing upright and stable (or is being held/tilted), and has switched off heating. It resumes automatically once placed on a flat, stable surface.

Where & how you can use Mill heaters

Can Mill heaters be used in wet rooms or bathrooms?

All Mill panel heaters, plus the floor heater CO1500MAXWIFI3, carry an IPX4 rating and are approved for bathroom zone 2. Other heater types are not rated for wet rooms and shouldn’t be used there.

Can I use Mill devices outdoors?

Only Mill’s dedicated outdoor/patio heaters are designed for outdoor use. Other Mill products are for normal indoor conditions — uninsulated spaces like garages or sheds expose them to rapid temperature/humidity swings that can damage the unit over time.

Can I leave a heater running unattended?

Panel heaters, oil heaters, and the Wi-Fi floor heaters CO1200WIFI3 and CO1500MAXWIFI3 can run unattended. Other floor heaters use an exposed heating element meant for supplemental, supervised use only.

Warranty & security

What’s Mill’s warranty policy?

Mill gives a 5-year warranty on most products bought after November 1, 2022 (2 years for business customers, and for purchases before that date; Mill Heat Pumps have separate terms). The warranty covers repair, replacement, or refund for manufacturing defects, at Mill’s discretion — it excludes misuse, transport damage, normal wear (batteries, filters, bulbs), wrong voltage/Hz, poor maintenance, environmental damage, incorrect installation, non-certified parts/unauthorized repairs, and software/connectivity issues. To claim, contact your authorized retailer with your receipt, serial number, and the product itself.

What is the Guaranteed Security Support Period?

Mill guarantees 10 years of security support from date of purchase on eligible products, covering firmware, cloud services, and the mobile app. Mill recommends keeping devices and apps updated to the latest version at all times.

Panel Heaters

Mill’s electric panel heaters use an aluminium heating element in direct contact with the air for fast, even heat at a relatively low surface temperature.

Why choose a panel heater?

The aluminium heating element heats the room quickly while keeping the surface temperature low enough to be safer to the touch than some other heater types.

How do I reset a Generation 2 panel heater?

Turn the heater off, then hold the gear button (bottom right of the display) while switching it back on; release when the display lights up. It resets to 22°C.

How do I reset a Generation 3 panel heater?

Turn off at the main switch, then turn on and immediately hold the gear button until “FR” appears (it cycles through “CH” → “CO” → “FR” first). It restarts and settles at 22°C.

How do I reset a Generation 3M panel heater?

Press the gear button, navigate with +/- to “Hr”, press gear to enter reset mode, select “YES”, and confirm. The display blinks twice, the heater restarts, and settles at 22°C.

How do I reset a Generation 4 panel heater?

Same process as Gen3M: gear button → navigate to “Hr” → gear to enter reset mode → select “YES” with +/- → confirm with gear. The heater restarts after a brief blank-screen moment.

No heat is coming from the panel heater. What should I do?

Check that the lightning-bolt symbol is lit (it indicates active heating). Reset the heater, set it to maximum (35°C), and check for warmth at the top vents within a few minutes. If it still doesn’t heat, return it to your retailer with your receipt.

My Mill convection/panel heater turns off before the room reaches the set temperature. What do I do?

This usually means the heater’s built-in sensor reads a different temperature than where you actually sit. Calibrate it: place a separate thermometer centrally in the room (not directly above any heat source) for 24 hours, then enter that reading via Settings → Calibration in the app, or follow the model-specific steps in your manual. Heaters with a mechanical thermostat can’t be calibrated.

What’s the difference between Mill steel and Mill glass panel heaters?

Functionally they’re identical — same heat output and performance. The only real difference is the front panel material, which affects surface temperature and look; the top area where heat is released gets significantly hotter on both and shouldn’t be touched during use.

What is the maximum surface temperature of Mill panel heaters?

It varies by model and wattage:

How do I set a day/night program on a Mill Steel/Glass panel heater?

The program activates at the exact time you set it on the heater, using day numbers (1=Monday … 7=Sunday). A power cut or switching the heater off erases the program.

• Day setback (e.g., Mon–Fri only): at your chosen start time, press the sun symbol → set the day with the arrows, confirm → set the target temperature, confirm → set the duration in hours, confirm.
• Night setback (every night): at your chosen start time, press the moon symbol → set the target temperature, confirm → set the duration in hours, confirm.

Example: day setback 7:30am–2:30pm at 17°C (7 hrs); night setback 10pm–6am at 18°C (8 hrs).

Can a panel heater be hard-wired via a connection box instead of a plug?

Yes — all Mill panel heaters ship with a standard plug by default, but can instead be installed with a wall-mounted junction/connection box. This must be done by a certified electrician.

How do I replace the control panel on a Gen3M/Gen4 panel heater?

Switch off and unplug the heater, remove it from its wall bracket, remove the two screws on the back of the control panel, lift it off gently (don’t pull on the cover), fit the new control panel, replace the screws, remount, and power back on. The heater will need to be re-paired in the app afterward (“+” → New device).

What size wall bracket do I need for my panel heater?

It depends on wattage and serial number:

Can I install a panel heater with curtain hangers?

Mill doesn’t make its own curtain rods, but third-party rods can be used, provided you keep the minimum clearances (10 cm above/below/front, 5 cm each side). Ask your retailer which rods fit your model.

Can a panel heater be installed vertically?

No — the heating element and air vents are designed to run horizontally. Mounting it sideways restricts airflow and can trigger the overheat protection.

Why have I lost functionality on my Generation 1 heater?

Gen1 heaters (produced in 2016) can’t receive over-the-air firmware updates, so they can’t be migrated to Mill’s newer AWS-based platform that powers features like electricity price optimization and Matter support. They still work standalone — set temperature, view room temperature, turn on/off — but have lost smart scheduling and other app-based features. This affects roughly 0.5% of Mill’s installed base.

Smart Plug

How do I reset a Mill Smart Plug?

Hold the Wi-Fi button until it turns red, release — it flashes red. Press once more to confirm the reset; the light flashes briefly and then goes out. To pair: “+” → New device → select product → select generation, and follow the app instructions.

Can a Smart Plug be used with devices other than heaters?

Yes, for devices up to 2300W. With its temperature sensor disabled, it acts as a simple Wi-Fi on/off switch (e.g., for a radio, fan, or lamp); with cooling mode enabled, it supplies power once the temperature in the app reaches your set threshold (inverting normal heat-mode logic). To disable the sensor, the plug must be set up as a standalone device (remove it from any room first). It must never be used for critical loads — heat pumps, water heaters, pipe heating, underfloor heating, fridges/freezers, etc.

What do the different lights on the Smart Plug mean?

• Green (flashing/solid): connecting / connected
• Purple: child lock — hold to activate, press 5× quickly to deactivate
• Blue: open-window function — hold to toggle on/off
• White: access point (alternative Wi-Fi connection, only active if enabled)
• Orange: Wi-Fi/soft reset (only possible once previously connected)
• Red: factory/hard reset
• Yellow: Matter reset (only visible once connected to Matter)

Wi-Fi Socket

What is a Mill Wi-Fi Socket?

A smart plug that makes a regular heater without built-in Wi-Fi compatible with the Mill app, giving it scheduling and timer functions. Rated for devices up to 2300W; not for use with heaters needing supervision or critical systems like pipe heating.

• Wi-Fi Socket 3: built-in temperature and humidity sensor, automatic power-consumption tracking, auto-detects wattage.
• Wi-Fi Socket (Gen 2): built-in temperature sensor; wattage must be entered manually for accurate statistics.

How do I reset a Gen2 Wi-Fi Socket?

Unplug, wait ~30 seconds, plug back in, then hold the button for 12 seconds until it flashes and goes dark.

How do I reset a Gen3 Wi-Fi Socket?

Unplug, wait ~30 seconds, plug back in, then hold the button for 7 seconds until it flashes and goes dark. Alternative Wi-Fi connection isn’t available on Gen3.

What is Timer / Cooling mode on the Wi-Fi Socket?

Cooling mode runs the opposite of normal heat mode — it supplies power only once the room exceeds your set temperature (useful for fans). The Timer function schedules on/off times through the week. The temperature sensor can also be disabled entirely, turning the socket into a basic scheduled on/off switch (e.g., for lamps). Never use it for critical systems like pipe or freezer heating.

Why does the Wi-Fi Socket ask for wattage on some setups but not others?

Gen3 has a built-in wattage meter and detects the connected heater’s wattage automatically. Gen2 lacks this and requires you to enter the heater’s wattage manually during setup.

There’s no light on my Wi-Fi socket. What do I do?

Unplug it for 10 seconds and plug it back in, checking whether the light comes on or the button makes it blink. If not, reset it (Gen2: 12-second hold after a 30-second unplug; Gen3: 7-second hold after a 30-second unplug). If the light still doesn’t appear, the unit is likely faulty — return it to your retailer with your receipt (warranty up to 5 years).

The Wi-Fi Socket is measuring too high a temperature. What do I do?

The socket’s own electronics generate some heat, so the sensor sits in the bottom-left corner to minimize interference — install it facing down (best) or facing right; avoid upside-down or facing-left orientations. If readings are still off after correct installation, calibrate it: app → Settings → Calibration → select device → enter the correct temperature.

Can the Wi-Fi Socket be used for things other than heaters?

Yes, up to 2300W — same as the Smart Plug: disable the temperature sensor for a basic on/off switch, or enable cooling mode to invert the logic. Never use it for critical systems (heat pumps, water heaters, pipe/underfloor heating, fridges/freezers).

Can the Wi-Fi Socket be used in bathrooms?

No — it has no IP rating for dust/water resistance. Use one of Mill’s IPX4-rated panel heaters in bathrooms instead, or a Floor Thermostat for heating cables.

What should the heater be set to when a Wi-Fi Socket is connected?

Set the heater’s own thermostat about 5°C higher than your desired room temperature, and set the actual target temperature on the socket in the app. Example: for 25°C, set the heater to 30°C and the socket to 25°C — the socket cuts power once 25°C is reached.

Floor Convection Heaters

How do I reset a CO1200WIFI3 or CO1500MAXWIFI3 (Gen3)?

Turn the heater off, then on, and immediately hold the gear/settings button until the display cycles “CH(L)” → “CO(L)” → “FR” — release on “FR”. It counts up and settles at 22°C.

How do I reset an SG1200WIFI, SG2000LED, or CO2200LEDMAX (Gen2)?

Turn the heater off, then hold the button with the three wavy lines (Wi-Fi button) while turning it back on; release once the display LEDs blink/reset. It defaults to 22°C.

Can the SG2000MEC or CO2200MECMAX be reset?

No — these models don’t support a reset.

The fan doesn’t work. What can I do?

Older floor heaters had fans; newer models dropped them, since testing showed only a small performance difference. If your fan has failed, the heater can still be used normally without it.

Why doesn’t my newer heater have a fan?

Mill’s testing found the fan added only 2–3% more performance while being the component most prone to failure. Removing it made the heater more durable and reliable, relying instead on natural convection for airflow.

My Mill convection heater generates no heat. What do I do?

Check the lightning-bolt symbol — it should be lit when actively heating. Reset the heater (SG2000MEC/CO2200MECMAX can’t be reset — set those to MAX instead), set the temperature to maximum (35°C), and check for warmth within a couple of minutes. If it’s still not heating, contact your retailer with your receipt or reach out to Mill support.

The lightning symbol is on, but there’s no heat. What do I do?

All Mill heaters since the 2013 season show a lit lightning-bolt symbol while actively heating. If it’s lit with no actual heat: reset the heater, set it to maximum (35°C), and wait a couple of minutes. If still no heat, the unit is likely faulty — contact your retailer with your receipt, or reach out to Mill support. (The same troubleshooting applies to oil heaters — see the Oil Heaters section.)

Oil Heaters

Why choose an oil heater?

Oil heaters don’t dry out the air the way a panel heater can, giving a more comfortable indoor climate, and they’re portable, free-standing units. They also retain heat after switching off, since the internal oil takes time to cool — the main trade-off is that they take longer to reach full temperature.

How do I reset a Mill Oil Premium heater?

Gen2 (AB-H1000DN, AB-H1500DN, AB-H2000DN): turn off at the main switch, hold the gear button while turning back on, release once powered on — it counts down to 22°C.

Gen3 (OIL1000WIFI3, OIL1500WIFI3, OIL2000WIFI3): turn off, then on, and within 5 seconds hold the gear button for ~20 seconds until “FR” appears — it counts up/down and settles at 22°C.

Models AB-H700MINI, AB-H1000MEC, and the JA-series (JA1000/1500/2000) have mechanical thermostats and cannot be reset.

How do I set the day/night program on a Mill Oil Premium heater (DN models)?

Applies to AB-H1000DN, AB-H1000DN Black/Glass, AB-H1500DN, AB-H2000DN. The program activates at the exact time you set it and is forgotten if power is lost or the heater is switched off.

• Day setback (Mon–Fri): press the sun symbol at your chosen time → set the day number with the gear button, confirm with the wavy-line button → set the setback temperature with the dial, confirm → set the duration, confirm.
• Night setback (every night): press the moon symbol → set temperature, confirm → set duration, confirm.

My Mill Oil Premium heater generates no heat. What do I do?

Check the lightning-bolt symbol is lit. Reset the heater (not possible on AB-H700MINI, AB-H1000MEC, or JA-series), set it to maximum (35°C, or MAX on the JA-series), and check for warmth within 5–10 minutes. If it’s still not heating, return it to your retailer with your receipt, or contact Mill support.

Do I need to change the oil in my oil heater?

No — Mill’s oil-filled heaters are maintenance-free and pre-filled at the factory for life; the oil never needs replacing or topping up. If a heater develops a leak, bring it (with your receipt) to your retailer, or contact Mill support.

My oil heater is making noises. Why?

Crackling sounds while heating up or cooling down are normal — they come from the oil’s temperature changes causing the surrounding metal to expand and contract.

The lightning symbol is on, but there’s no heat. What do I do?

See the identical troubleshooting under Floor Convection Heaters above — reset the heater, set it to maximum (35°C), wait a couple of minutes, and contact your retailer or Mill support if it still won’t heat.

Mill Sense (Air Quality Sensor)

What is a Mill Sense?

A sensor that measures and logs temperature, humidity, and air quality, viewable in the Mill app. It runs on a built-in lithium battery (1–3 months per charge) or permanent USB power (though charging can add heat that skews readings). It can also auto-calibrate Mill heaters and Wi-Fi sockets. Mount it on a wall at chest/shoulder height for the most accurate “felt” temperature reading.

How do I reset Mill Sense?

Make sure it’s fully charged, then press and hold the button for 12 seconds until it blinks; once the blinking stops, it’s reset and ready to pair.

Can Mill Sense detect mold or moisture damage?

Not directly — it has no dedicated moisture/mold sensor, but its TVOC sensor can give an indirect indication that mold-related particles may be present.

Mill Sense is showing incorrect values. What do I do?

New sensors (or ones moved to a new location) need about 72 hours to calibrate and stabilize. If a value reads 0 in the app, try resetting the device (hold the button 12 seconds until it blinks, then goes dark). If TVOC, eCO2, or particle readings still don’t appear after another 72-hour period, the sensor may be defective — return it to your retailer with your receipt for warranty replacement.

How long does the Mill Sense battery last?

Roughly 1–3 months, depending on how often it updates (default: every 15 minutes). Battery level is visible in the app.

Can Mill Sense be used in bathrooms?

No — it has no IP rating and isn’t suitable for wet rooms or uninsulated spaces.

What do the Mill Sense LED colors mean?

Press the button to check air quality:

• Blue: room is cold (below 18°C)
• Green: good air quality
• Yellow: approaching poor/moderate air quality — try airing out the room
• Red: one or more values above the recommended level — increase ventilation or adjust humidity as needed

How often does Mill Sense update its values?

Every 15 minutes by default; adjustable in the app down to once per minute, though faster updates use more battery, so 15 minutes is recommended.

Mill Air Purifiers

Mill’s Silent Pro and Silent Pro Compact air purifiers use multi-stage filtration, controllable via the Mill app.

What is the Mill air purifier effective against?

A pre-filter catches large particles before air reaches the True HEPA13 medical-grade filter, removing 99.97% of particles down to 0.3 microns — including pollen, mold, bacteria, and viruses. An activated carbon filter then handles gases and odors (exhaust fumes, smoke, food smells), and an antibacterial coating prevents bacterial growth on the filter itself.

How do I reset a Mill Silent Pro Compact (APSILENTCO)?

Turn the device off, then on, and hold the Fan speed/Mode button for 20 seconds until all icons blink three times.

How do I reset a Mill Silent Pro (APSILENTPRO)?

Turn the device off, then on, and within 10 seconds hold [MODE] for 10 seconds to trigger a hard reset.

My Mill Air Purifier shows unexpectedly high readings. Why?

Usually dust buildup on the particle sensor, located above the air intake on one side of the unit. Vacuum the sensor area regularly to keep it clear (see your manual for the exact location).

What do the lights and symbols on the control panel mean?

The filter-change indicator is always visible when the display is on, showing remaining filter life by color:

The air-quality light (IAQ) shows real-time air quality (default: based on particle values, or optionally particles + TVOC / TVOC only, selectable in the app):

Why does the device vibrate on the floor?

It has four shock-absorbing feet — if all four aren’t firmly on the floor, the unit can vibrate while the fan runs. Make sure it’s sitting level and flush with the floor.

How often does the filter need replacing?

At least every 12 months, though actual air quality can shorten that. The Silent Pro also tracks real particle measurements to notify you when a replacement is actually needed. Replacement filters are sold through retailers that carry the Air Purifier.

What’s the difference between the Silent Pro and Silent Pro Compact?

Both use the same HEPA13 filter and run at the same noise levels, controlled through the same app interface.

• Compact: recommended for rooms up to 55 m²; sensors cover temperature, humidity, and particles.
• Silent Pro (full size): recommended for rooms up to 115 m² (larger filter and fan); its sensor also adds TVOC and eCO2 on top of particles, humidity, and temperature.

Outdoor / Patio Heaters

How does a Mill outdoor heater produce heat?

Using short-wavelength infrared light, which warms objects directly (like sunlight) rather than heating the surrounding air — giving over 90% heat efficiency and near-instant warmth once switched on. Because it’s directional, objects outside the direct beam get far less warmth.

Can I use the same remote control for multiple outdoor heaters?

Yes — it’s an infrared signal, so just point the remote at whichever unit you want to control. Models with power regulation (CB2000BT-ULG, CB2000PLUSS, CB2000FLOOR, CB2000GD, CB3000GD) share one remote type; on/off-only models (CB2000BASIC, CB1500, CB1500G, CB1500GF, CB2000GT) share another.

The outdoor heater doesn’t respond to the remote. What do I do?

Usually dead batteries or a faulty remote — remember the remote is directional and must point at the heater to work.

Can an outdoor heater be mounted upside down?

Yes, all wall-mounted models support inverted mounting — useful if you need the power cable on the other side, or you’re fitting it under an overhang. Just keep the minimum clearances from the user manual.

The indicator light doesn’t come on at all. What do I do?

First check the power outlet works and meets the safety requirements in the manual. If the light still won’t come on, the heater likely has a fault.

Can an outdoor heater stay outside all year round?

Yes, they’re built for year-round outdoor use — with one exception: near saltwater, Mill recommends cleaning the heater and storing it indoors during long unoccupied periods to prevent rust.

Can I control an outdoor heater with an app?

Only the CB2000BT-ULG model, via the “Mill Outdoor Heating” app.

What is ULG and ULG+?

ULG (“Ultra Low Glare”) is a heating element design that gives off much less red light than standard infrared heaters, for a more pleasant glow. ULG+ is an improved, more efficient version.

I’ve lost my remote control. What do I do?

Replacement remotes are sold directly through Mill in Norway; availability elsewhere varies. Contact Mill via the app or support site’s message function to ask about a replacement.

I’ve downloaded the app but can’t find my outdoor heater in it. Why?

For safety, the heater only broadcasts Bluetooth while it’s switched on and heating. Turn it on via the remote or the side button, and the app will then detect it. You can also enable “Device Bluetooth control” in the app so it stays discoverable whenever the power switch is on, letting you turn on heat directly from your phone.

How do I attach an outdoor heater to the wall?

Standard wall screws for concrete and wood are included, but they may not suit every wall type — check with a hardware store if you’re unsure.

The indicator light turns on, but the heater doesn’t produce heat. What do I do?

This points to a faulty heating element. It’s a replaceable part with a 2-year warranty from purchase, and is replaceable on most models (with some exceptions) — contact Mill for assistance.

Can I replace the heating element myself?

Yes, on most models — though there are a few exceptions. Contact Mill if you run into trouble.

What power levels does the Mill Patio Heater offer?

Six levels, adjustable via the wireless remote: 33% – 50% – 60% – 70% – 80% – 100%.

Matter, API & Homey Integration

Matter

How do I activate Matter on a Mill device?

Supported on the WiFi Gen4 panel heater, Gen3 panel heater, Gen3 oil heater, and the Mill Smart WiFi Plug, for use with Amazon Alexa, Google Home, or Apple HomeKit.

1. Open the Mill Norway app and log in.
2. Go to Settings → Activate Matter, and choose your device.
3. Follow the step-by-step guide.
4. You’ll receive a Matter QR code and PIN by email.
5. In your smart-home app, add the Mill device, press its Wi-Fi button, and follow the prompts, using the QR code/PIN to connect.

Note: activating Matter disconnects the device from Mill Cloud — you can’t use Matter and the Mill app on the same device at the same time (see below).

How do I remove Matter from a device?

• Wi-Fi Gen4 panel heater: gear button → navigate with +/- to “rA” → gear → navigate to “YES” → gear to confirm master reset. It can now be re-added in the Mill app.
• Smart Wi-Fi Plug: with the plug powered, hold the Wi-Fi button until it turns yellow, release, and confirm with one press. It restarts in 2–3 seconds and can be re-added.
• Wi-Fi Gen3 panel heater: turn off, then on, and hold the settings button before the countdown ends; after 20+ seconds “rA” appears — release then. It restarts in 6–7 seconds and can be re-added.

Can I use Matter and the Mill app at the same time?

No — you have to choose one control method per device; they can’t both manage the same device simultaneously.

API

Does Mill offer a public API?

Yes — Mill provides an open API for developers, documented at http://mn-be-prod-documentation.s3-website.eu-central-1.amazonaws.com/#/, covering endpoints, integration methods, and usage guidelines.

Homey

How do I activate Homey integration?

1. Set up your device in the Mill Norway app first (“+” → follow the pairing guide).
2. Install the Homey app and make sure your Homey hub is set up.
3. In Homey, go to Devices → “+” → New device, search “Mill WiFi”, and choose your product.
4. Sign in with your Mill Norway account credentials — the device is then detected and added.

You can control the device from both Homey and the Mill Norway app at the same time.