The first confusing thing about a Korean apartment boiler is that the number on the controller may not be the room temperature. In 실온 mode it usually refers to indoor air; in 온돌 mode it may refer to the water circulating under the floor. The same number can therefore mean something very different.
This guide is for renters and new residents using a wall-mounted controller for an individual gas boiler. District-heated apartments and older controllers can work differently, so start by identifying the exact model rather than pressing buttons at random.
Illustrative controller only. Button names, displays, and functions vary by manufacturer and model.
1. Photograph the controller, boiler brand, and model label.
2. Check whether the display says 실온, 온돌, 온수, 외출, or 예약.
3. Make one small change, wait for the floor and room to respond, and note the result.
4. If an error code remains, use the manual for that exact model or contact the landlord, building office, or manufacturer.
Identify your heating system before changing settings
Look for the boiler itself, often installed in a utility balcony or enclosed service area. If your apartment has its own gas boiler, it is usually 개별난방 (individual heating). If the building supplies heat centrally, you may have 지역난방 (district heating) or 중앙난방 (central heating). Those systems may use a room controller but not the same gas-boiler functions described here.
Take two photos: the front of the wall controller and the model-information sticker on the boiler. Do not remove the metal cover. Search the manufacturer’s official support page using the model number, because identical-looking buttons can behave differently across generations.
A model photo is more useful to a landlord or technician than a description such as “the white boiler.” Hide the serial number before posting it publicly.
The Korean words you actually need
| Korean | Meaning | What to check |
|---|---|---|
| 전원 | Power | Turning it off may also stop hot water and freeze-protection operation on some models. |
| 난방 | Heating | Starts or stops floor heating. |
| 실온 / 실내 | Room temperature | Uses the controller’s room-temperature sensor on many models. |
| 온돌 | Floor-heating mode | Usually controls heating-water temperature, not the floor surface temperature. |
| 온수 | Domestic hot water | Controls taps and shower water, separately from space heating on many units. |
| 외출 | Away mode | Behavior varies: minimum heating, timed heating, or another low-heat routine. |
| 예약 | Timer / reservation | The number may mean a delay, an interval, or a run time depending on the model. |
Room temperature mode versus ondol mode
실온: the controller watches the air
On many controllers, room-temperature mode uses a sensor inside the wall unit. It works best when that controller is in a representative part of the home. A controller beside a drafty entrance may read colder than the living area; one beside direct sunlight or another heat source may read warmer.
If the room never feels stable, check the controller’s location before raising the target repeatedly. Curtains, an open balcony door, or a nearby appliance can change what the sensor sees.
온돌: the boiler watches heating water
Official Rinnai manuals describe ondol mode as controlling the temperature of the water sent through the floor-heating system. The displayed target is therefore not the temperature you should expect on the floor surface or in the air.
Ondol mode can be useful when the wall sensor sits in a poor location, but there is no universal “correct” number. Manufacturer ranges vary by model. Start with the current or manual-recommended setting, adjust in small steps, and allow time for the concrete floor to warm before changing it again.
A practical setup routine
- Confirm the mode. Look for 실온/실내 or 온돌 on the display.
- Record the current setting. Take a photo so you can return to it.
- Change only one thing. Do not change the mode, target, timer, and hot-water temperature together.
- Wait. Floor heating has thermal lag. The room may continue warming after the burner stops.
- Check more than comfort. Listen for unusual noise, look for water leakage, and note whether the error code returns.
- Compare usage over several similar days. One unusually cold day is not a fair test of a setting.
Avoid copied “perfect temperature” charts unless they come from your exact manual. Insulation, floor construction, room size, outside temperature, and controller location all affect the result.
Hot water without space heating
In warm weather, many models allow 온수 (hot water) while 난방 (space heating) is off. The button sequence differs. Confirm the hot-water indicator on the display, then test one tap briefly.
If the shower alternates between hot and cold, do not immediately raise every temperature. Check whether other taps are running, whether the water-flow rate is very low, and whether an error code appears. Persistent problems need the model manual or a technician.
Away mode and freeze prevention
외출 is not identical across brands. Some Rinnai manuals describe it as periodic minimum heating, while other models use a different routine. Kiturami’s winter guidance advises not switching the boiler completely off during freezing weather and emphasizes keeping power connected and pipes insulated.
For a short absence, lowering the target may be simpler than changing to an unfamiliar away program. For a long winter absence, check the exact manual and ask the building manager about exposed pipes. Automatic freeze protection may require electricity, gas, and water to remain available.
What to do when an error code appears
- Photograph the full display and write down the code exactly, including letters or leading zeros.
- Check whether heating, hot water, or both have stopped.
- Look from a safe distance for visible leakage. Do not remove the boiler cover.
- Find the code in the official manual for the exact model.
- If the manual permits one reset, follow that sequence once. Repeated resets can hide a persistent fault.
- Send the photos and model number to the landlord, building office, or authorized service center.
Do not assume that the same number means the same fault across Navien, Rinnai, and Kiturami. Error-code lists found on forums may describe a different controller.
Gas smell or carbon-monoxide concern
Do not operate light switches, plugs, the boiler, or other electrical equipment. Move people outside and call 119 or the city-gas provider from a safe location. Seoul’s official safety guidance says a minor leak may be handled by closing the gas valve and opening doors to ventilate, but only do so if it is immediately safe. Do not stay inside to investigate.
Headache, dizziness, nausea, confusion, or unusual sleepiness can be signs of carbon-monoxide exposure. Move into fresh air and call 119. Do not re-enter until emergency or gas-safety personnel say it is safe.
Useful Korean phrases
- 보일러가 작동하지 않아요. — The boiler is not working.
- 온수는 나오는데 난방이 안 돼요. — Hot water works, but the heating does not.
- 에러 코드가 떠요. — An error code is showing.
- 모델명 사진을 보낼게요. — I will send a photo of the model name.
- 가스 냄새가 나요. — I smell gas.
Official references
- Rinnai Korea — controller manual showing model-specific heating modes
- Kiturami — 2026 winter freeze-prevention guidance
- Seoul Metropolitan Government — safety tips for gas leakage
This guide explains common controls; it is not a repair manual. Use the official instructions for your exact model, and leave gas, combustion, electrical, and internal boiler work to qualified technicians.
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