Heat mode (sun)
The unit runs as a heat pump and warms the room towards the set temperature, taking heat from the outdoor air.
What pressing it does
Select it with MODE and set the temperature. Airwell explains that “a heat pump conditioner heats a room by taking heat from outside air” and that its output falls when it is very cold outdoors; Midea recommends another heater alongside it in that case. Mitsubishi Electric’s MSZ-LN heats from a 10 °C setting upwards.
What it does not do
It does not blow warm air the moment you press it: Fujitsu runs the fan very low for about 3–5 minutes first and Samsung says the fan may not run for 3–5 minutes, to avoid a cold blast.
Makes differ, check your unit’s manual: the same drawing can mean different things on different brands, and only your model’s manual says exactly what a button does and which modes it works in.
- What it looks like
- A sun: a circle with short rays around it, beside or instead of the word HEAT.
- Names makers use
- HEAT (Midea, Fujitsu, Panasonic); Heating (Airwell); Heat (Samsung)
Where makers differ
Midea and Airwell draw a sun; Samsung prints Heat. Cooling-only units have no heat mode at all — the Daikin web manual cited on the cool page lists only COOL, DRY and FAN — so the sun never appears on their remotes.
Often confused with
The heat pump has paused heating for a few minutes to melt frost off the outdoor unit’s coil. Heating resumes by itself.
Other symbols with the same shapes
Sources
No single published standard defines air-conditioner remote icons, so this meaning is taken from 5 makers’ own manuals, each fetched and read on the date shown:
- Airwell: Airwell — RC08W remote control manual (PDF) — Sun icon = “Heating”; “A heat pump conditioner heats a room by taking heat from outside air. The heating efficiency will fall off when the outdoor temperature is very low.” Cold draft prevention: the indoor fan waits until the coil has warmed up. Checked 2026-09-26.
- Midea: Midea — Remote controller owner’s manual, RG51A(2)/E and RG51B(2)/E (PDF) — HEAT mode: press MODE, set the temperature and fan speed; “As outdoor temperature drops, the performance of your unit’s HEAT function may be affected … we recommend using this air conditioner in conjunction with other heating appliances.” Checked 2026-09-26.
- Fujitsu General: Fujitsu General — Operating manual, wall-mounted 18/24RLB and 30/36RLXB (US, PDF) — Notes in HEAT mode: “At the beginning of the operation, the indoor unit operates at very low fan speed for about 3–5 minutes for preparation.” HEAT set range 16–30 °C. Checked 2026-09-26.
- Samsung: Samsung — Wind-Free 2.0 air conditioner user manual, AR**TSFA*** (PDF on Samsung HVAC’s document store) — Heat mode: “the fan may not operate for about 3 to 5 minutes at the beginning to prevent cold blasts.” Checked 2026-09-26.
- Mitsubishi Electric: Mitsubishi Electric — MSZ-LN indoor unit service manual OBH766 revised edition B (PDF, UK library) — 9-4 HEAT operation: setting range 10–31 °C; cold air prevention stops the indoor fan or runs it very low while the coil is cold or defrosting. Checked 2026-09-26.
Written in our own words; quotations are the makers’ wording.