If your boiler suddenly stops and the thermostat shows a number or a letter-number code, don’t panic. Most codes point to a short list of causes: ignition failure, low heating water, freezing pipes, overheating, or a communication problem.
This guide focuses on Korean domestic boiler models commonly used in apartments and officetels in South Korea, not overseas models. It covers four brands: Navien (경동나비엔), Kiturami (귀뚜라미), Rinnai (린나이) and Daesung Celtic (대성쎌틱). It provides selected error codes documented in official Korean manufacturer guides. It is not a complete list of every code.
Why the Same Code Can Mean Different Things
Error codes depend on the brand and the model, not only the brand. Daesung’s official FAQ lists A6 as an ignition failure on one product line and as overheating on another. Kiturami uses 01/02/03 on its Condensing Premium models but E001/E002/E003 on its ECO Condensing models. Navien uses E03 or E003 for ignition failure on certain models. Always check the exact model before using a code guide.
So before you trust any code table, including this one, check three things: the brand, the model name, and the code on the display.
How to Find Your Korean Boiler Model
- Brand: the logo on the front of the boiler, usually in the boiler room, balcony utility room or kitchen side room.
- Model name: printed on the nameplate on the side or front of the unit.
- Error code: shown on the wall thermostat (the control panel in your living room) or on the boiler’s own display.
Take a photo of the nameplate and the thermostat screen. You will need both if you call for service. If you are not sure how to read the wall thermostat, see our guide to the boiler panel.
Quick Error Code Reference
These are model-specific examples, not universal codes for every boiler from each brand. Check the detailed sections before taking action.
| Problem type | Code examples | What to do |
|---|---|---|
| Ignition failure | Navien E03, Kiturami 01·02·03, Rinnai 11·12, Daesung A6 (on applicable models) | Check gas supply; call service if it repeats |
| Freezing, freeze protection or low heating water | Navien E50, Kiturami 39·95, Rinnai 15·89, Daesung A9 (freeze-protection operation, on applicable models) | Do not force restarts; check for frozen pipes or water level |
| Overheating | Navien E16, Kiturami 96, Rinnai 16, Daesung A4·AA (on applicable models) | Stop using the boiler and call service |
| Gas alarm | Navien E14, Kiturami 97 (on applicable models) | Stop using, close the gas valve, ventilate |
| Exhaust problem | Rinnai 90·99 | Stop using and call service |
The brand sections below explain each code in more detail.
What to Check First
Before anything else, write down the brand, model, code, symptom (no heating, no hot water, stops mid-operation) and when it started.
Do not turn the power off and on repeatedly, and never open or repair the boiler yourself. If you smell gas or exhaust fumes, or see overheating or leaking water, stop using the boiler and get professional help.
If the thermostat shows nothing at all and the boiler has no power, this is not an error code problem: see our guide on what to do when the boiler won’t turn on. If the problem is that you have no hot water, see our checklist.
Navien Boiler Error Codes (경동나비엔)
The codes below come from Navien’s official NCB311 manual. Other Navien models may use a different format or meaning.
| Code | Meaning | Recommended action |
|---|---|---|
| E03 | Ignition failure | Check gas supply |
| E04 | False flame detected | Call service if it repeats |
| E05 | Heating supply temperature sensor error | Call service |
| E09 | Blower fan error | Call service |
| E11 | Water level error | Call service |
| E12 | Flame lost during combustion | Call service |
| E14 | Gas alarm | Stop using and take safety measures |
| E16 | Heat exchanger overheating | Stop using and call service |
| E28 | Heating pipe leak related | Check for leaks, then call service |
| E50 | Freezing | Do not run the boiler; call service |
E03: Ignition Failure
E03 means the boiler could not light or could not detect the flame. If there is no gas smell, you can check that the gas valve near the boiler is open. Look from outside to see whether the exhaust pipe or drain hose is crushed or blocked, but do not remove or repair the exhaust pipe. If E03 keeps coming back, call service.
E16, E28 and E50: Overheating, Leak and Freezing
E16 means the heat exchanger got too hot and a safety device tripped, so stop using the boiler. E28 relates to a leak in the heating pipes, so check for water around the boiler and under the manifold (the pipe distributor). E50 indicates freezing. Forcing the boiler to run can damage parts and pipes.
Kiturami Boiler Error Codes (귀뚜라미)
Kiturami uses different code systems for different product lines. Condensing Premium models show 01, 02, 03 and so on. ECO Condensing models show E001, E002 and E003 instead. The table below covers the Condensing Premium line and follows Kiturami’s official self-diagnosis material.
| Code | Meaning | Recommended action |
|---|---|---|
| 01·02·03 | Ignition or flame detection error | Check gas supply; restart per the manual |
| 04 | Water temperature sensor error | Call service |
| 05 | Overheat sensor error | Call service |
| 06 | Blower rotation detection error | Call service |
| 07 | Blower rotation error | Call service |
| 08 | Thermostat communication error | Call service |
| 39 | Low water temperature (1°C or below) during freeze protection, on applicable models | Check for frozen pipes |
| 95 | Low heating water | Check automatic water refill |
| 96 | Overheat safety device activated | Stop and call service |
| 97 | Gas or exhaust-related detection alarm, on applicable models | Take safety measures immediately |
If your Kiturami shows E001, E002 or E003 (ECO Condensing): these indicate a flame detection or ignition problem. Check that the gas valve is open, then call Kiturami service if the code returns. Don’t apply the numbers in the table above to this line.
01, 02, 03: Ignition-Related Errors
They show up when the flame is not detected properly or a safety shutdown happens. Some models let you reset from the thermostat. If gas supply is normal and the code repeats, the igniter or sensor may need service.
08: Thermostat Communication Error
The boiler and the wall thermostat are not exchanging signals. Do not disconnect or reconnect the wiring yourself.
95: Low Heating Water
This is the typical “not enough water” code. Some models refill automatically and then run normally. If refilling doesn’t happen or the code stays, there may be a water supply problem or a leak.
97: Gas or Exhaust-Related Alarm
On applicable models, 97 is a detection alarm that can relate to gas or exhaust gas. Do not restart the boiler. Close the gas valve, ventilate naturally, avoid switches and flames, and call your gas supplier or emergency services from a safe place. 97 does not mean the same thing on every Kiturami product, so check your model’s manual.
Rinnai Boiler Error Codes (린나이)
Some Rinnai gas boilers show faults as numbers such as 11, 12, 15, 16. The table follows Rinnai’s official manual for domestic models (including the RC600).
| Code | Meaning | Recommended action |
|---|---|---|
| 02 | Repeated reset error | Restart per the manual |
| 07 | Long hot water use detected | Check hot water taps |
| 11 | Initial ignition failure | Check gas supply |
| 12 | Flame went out during operation | Check gas supply |
| 14 | Safety circuit or overheat protection error | Stop using and call service |
| 15 | Water circulation error (on applicable models) | Check water supply and freezing |
| 16 | Overheat detected | Check that the heating manifold valves are open |
| 17 | Leak detected | Check pipes and manifold for leaks |
| 89 | Complete freeze detected | Call service |
| 90·99 | Exhaust error | Stop using and call service |
11: Ignition Failure
This appears when the first ignition fails. If there is no gas smell, check whether other gas appliances work and whether the boiler’s gas valve is open. If the gas supply to the building is cut off, contact your city gas company. If the supply is fine and 11 repeats, ask Rinnai service for an inspection.
15 and 16: Water Circulation and Overheating
15 shows up on some models when heating water doesn’t circulate, so in cold weather check for frozen pipes and water supply. On some models 15 has another meaning, so read your manual first. 16 is an overheating code. Some models ask you to confirm that the manifold valves are open. If it repeats, stop the boiler and call service.
17 and 89: Leak and Freezing
17 can mean water is leaking or the boiler keeps refilling. Look around the unit, pipe joints and under the manifold. 89 means a heavy freeze on some models. Don’t try to thaw it with a heater, and don’t force a restart.
Daesung Celtic Boiler Error Codes (대성쎌틱)
Check your product type first. The same Daesung code can mean different faults on different products, such as gas boilers, oil boilers and electric boilers. For example, A6 is an ignition failure on some gas boilers but overheating on other product lines. A4 also differs by product. The table follows Daesung’s official gas boiler self-diagnosis page.
| Code | Meaning | Recommended action |
|---|---|---|
| A6 | Ignition failure (applicable gas boilers) | Check gas supply |
| A5 | Overheat-prevention (dry-fire) wire break, on applicable models | May relate to low heating water or pump issues; check the manual and call service |
| A4 | Overheating (applicable models) | Stop using and call service |
| A7 | Control device error | Call service |
| A9 | Freeze-protection operation (applicable gas boilers); does not necessarily mean the pipes are frozen | May clear automatically as the heating water warms up; if it stays or pipes are frozen, call service |
| AA·10 | Heating water overheat related (applicable models) | Check heating circulation |
| Ab | Heating temperature sensor error | Call service |
A6: Ignition Failure
On some gas boilers it means ignition was tried but no flame was detected. With no gas smell, check the gas valve near the boiler and whether your unit still has gas. If gas is normal but the boiler won’t light, the igniter or sensor needs inspection. On other Daesung products A6 means overheating, so confirm your model.
A9 and AA: Freeze Protection and Overheated Heating Water
On applicable Daesung gas boilers, A9 indicates freeze-protection operation. It does not necessarily mean the pipes are already frozen. The code may clear automatically as the heating water warms up. If it remains or the pipes are frozen, contact a professional.
AA can occur when heating water can’t circulate and gets too hot. You can check from outside whether the manifold valves are closed, but repeated AA needs a service check.
Codes to Watch in Cold Weather
Frozen pipes and low water are common causes of winter shutdowns:
- Navien: E50 (NCB311), freezing
- Kiturami: 39 and 95 (some models), low water temperature in freeze protection, low heating water
- Rinnai: 15 and 89 (some models), water circulation error and freezing
- Daesung: A9 (some models), freeze-protection operation
These are not the same fault under different names. They are examples of cold-weather codes, and the exact cause depends on your model.
Before a cold snap:
- Check that the boiler is plugged in and powered.
- Check insulation on exposed water and heating pipes.
- Check for cold drafts at the boiler room window or pipes. Never block the boiler’s required ventilation openings.
- If you will be away for a long time, check your manual for the freeze-protection setting.
- If pipes are already frozen or leaking, get professional help.
Turning off all power to the boiler can disable automatic freeze protection on some models. Don’t switch everything off just to “be safe” in winter.
When to Stop Troubleshooting and Call for Service
Not every code is something you can fix.
- Simple setting problem: check the manual
- Suspected gas supply cut: contact the gas supplier
- Low heating water: check whether your model refills automatically
- Sensor or communication error: call service
- Gas alarm: stop using immediately and take safety measures
- Repeated overheating: stop the boiler and call service
- Exhaust error: stop using and have the exhaust system checked
- Frozen or leaking pipes: call a professional
If you smell gas, don’t use switches, outlets, or your phone inside. Close the gas valve if you can reach it safely, open windows, and leave the area. Once you are outside in a safe place, call 119 or your gas supplier. Don’t wait for your landlord to reply. Never take apart the boiler, combustion unit, gas pipes or exhaust pipe.
Boiler Service Numbers
- Navien: 1588-1144
- Kiturami: 1588-9000
- Rinnai: 1544-3651
- Daesung Celtic: 1588-8577
If you need language assistance, ask your landlord or a Korean-speaking contact to help with the call. Have your model name, the code and the symptom ready, and a photo of the thermostat screen helps.
How to Contact Your Landlord in Korean
If you rent, tell your landlord or building manager about the code. You can copy and paste these:
- 보일러에 에러코드가 떴어요. (The boiler is showing an error code.)
- 에러코드는 [코드]이고, 보일러 브랜드는 [브랜드]예요. (The code is [code] and the brand is [brand].)
- 난방이 안 되고 있어요. / 온수가 안 나와요. (The heating isn’t working. / There is no hot water.)
- 수리 기사님 방문 가능한 시간을 알려주세요. (Please tell me when a repair technician can visit.)
Send the photo of the nameplate and the thermostat screen along with the message.
Frequently Asked Questions
Can I turn the boiler off and on when an error appears?
Only if your model’s manual says to restart. If you suspect a gas leak, overheating, an exhaust problem or severe freezing, don’t restart. Get it inspected.
Why do online explanations of the same code differ?
Brands and models use different code systems. Even within one brand, the same number can mean a different fault depending on the product type.
Should I turn off the boiler during a cold snap?
On some models the power must stay on for freeze protection to work. Check your model’s freeze-prevention instructions, especially if you are away for a while.
If the code disappears, do I still need a repair?
Some errors clear by themselves, but if the code repeats or heating or hot water still doesn’t work normally, get it checked.
Summary
When an error code appears, identify the brand, model and code first. The four brands use different code systems, and the meaning can change even within one brand depending on the model. In winter, watch for low water and frozen pipes. If you suspect a gas leak, overheating or an exhaust problem, don’t repair anything yourself and contact the official service center or your landlord.
Sources and References
- Navien NCB311 Official Manual
- Kiturami Official Self-Diagnosis Manual (villa-type Condensing)
- Kiturami Official Thermostat Code Guide (NCTR-5000)
- Rinnai Official Boiler Manual
- Rinnai Official Error 11 Guide
- Daesung Celtic Official Error Code Self-Diagnosis
Written based on official manufacturer materials as of October 29, 2026. Models and codes can differ, so always check your own model’s manual and the manufacturer’s latest guidance.
Photo by mostafa mahmoudi on Unsplash