- Boilers
- Tankless gas water heater
LC
Rinnai LC on a tankless water heater: scale build-up
Risk level
Medium
Proceed carefully and stop if the check is unclear.
Urgency
Medium
Quick answer
The heater has detected scale build-up in the heat exchanger. Book a heat exchanger flush with a licensed professional. Rinnai lets you run the heater temporarily by pressing On/Off 5 times until the flush is done.
Safety first
Stop and check this first
- Do not rely on temporary restarts. Rinnai says repeated LC codes will eventually lock out the heater and that damage caused by lime build-up is not covered by the warranty.
- If you smell gas: do not try to light any appliance, do not touch any electrical switch and do not use any phone in the building. Call your gas supplier from a neighbor's phone and follow its instructions; if you cannot reach it, call the fire department.
Safe checks you can perform
- Read the exact code
- Temporary restart until the flush
- Water treatment, set temperature and last flush
- Recent code history on the controller
- Heat exchanger flush by a licensed professional
Leave these tasks to a qualified professional
- Do not attempt this professional task: Recommend water treatment
- Do not attempt this professional task: Flush the heat exchanger
- Do not attempt this professional task: Reset the LC count
What a technician must be able to justify
Technician visit
These are the steps they must carry out and show you. Tick them as they work: if steps are skipped, do not accept a part swap.
These are not instructions for opening or handling the equipment yourself. They are the checks that should support a technical conclusion.
Recommend water treatment
What they doThe professional checks the water against Rinnai's water quality section and advises on treatment, such as the scale control system Rinnai offers.
They must show youthe water quality result or reason for the advice.
In writingthe treatment recommended or installed.
Flush the heat exchanger
What they doThe professional flushes the heat exchanger with undiluted food grade white vinegar using a circulating pump, then rinses it and cleans the inlet filter, as in the Value Series manual.
They must show youthe code cleared after the flush.
In writingthe flush date and the procedure used.
Reset the LC count
What they doIf the LC code does not clear on its own after the flush, the professional uses the PC board reset Rinnai describes in its troubleshooting guide, or calls Rinnai technical assistance for reset information.
They must show youthe heater back in normal operation.
In writingthat the LC count was reset.
Before accepting a part or repair
Nothing has been shown yet. Do not accept a part swap based on the code alone.
Follow these steps
Note: Follow the documented order. An error code identifies the affected system, but it does not prove by itself which part has failed.
Read the exact code
- Who:
- you.
- How:
- look at the controller. On Value Series models the display alternates between LC with a number (LC0 to LC9) and the set temperature, and the controller keeps beeping.
- Result that matters:
- confirming it is LC and noting its number.
- If it shows LC with a number:
- it is scale; continue with this page.
- If it shows a different code:
- see that code's page; LC advice does not apply.
- Evidence to keep:
- photo of the display with the date.
Evidence: Rinnai USA troubleshooting tankless water heater diagnostic codes · Rinnai Value Series tankless water heater installation and operation manual
Temporary restart until the flush
- Who:
- you.
- How:
- press the On/Off button on the temperature controller 5 times, as the Value Series manual describes. Rinnai's troubleshooting guide says the heater then runs for 70 hours and locks out again with another LC code.
- Result that matters:
- hot water while you arrange the flush.
- If the heater runs:
- book the flush now; repeated LC codes will eventually lock the heater out.
- If it does not restart:
- leave it off and call a licensed professional.
- Evidence to keep:
- date of each temporary restart and the LC number shown.
Evidence: Rinnai USA troubleshooting tankless water heater diagnostic codes · Rinnai Value Series tankless water heater installation and operation manual
Water treatment, set temperature and last flush
- Who:
- you.
- How:
- check whether a water treatment or scale control system is installed, what temperature the heater is set to and when the heat exchanger was last flushed.
- Result that matters:
- whether scale will keep coming back after the flush.
- If there is no treatment and the water is hard:
- ask the professional about treatment; Rinnai says hard water must be treated.
- If treatment is installed:
- ask the professional to check it is working.
- Evidence to keep:
- maintenance invoices and photo of the set temperature.
Evidence: Rinnai Value Series tankless water heater installation and operation manual
Recent code history on the controller
- Who:
- you.
- How:
- on the MC-91-2 controller of Value Series models, press and hold On/Off for 2 seconds and, while holding it, press the up button. The last 9 codes flash one after another; in this history LC appears as 00. Repeat the same keys to exit.
- Result that matters:
- whether LC is the only code stored.
- If only 00 appears:
- the issue is scale; the flush is the next step.
- If other codes appear too:
- note every code, because they change the diagnosis.
- Evidence to keep:
- photo or video of the code sequence with the date.
Evidence: Rinnai USA troubleshooting tankless water heater diagnostic codes · Rinnai Value Series tankless water heater installation and operation manual
Heat exchanger flush by a licensed professional
- Who:
- a licensed professional.
- How:
- with the power disconnected and the hot and cold shutoff valves closed, connects a pump and hoses to the service valves and circulates 4 gallons (15.1 liters) of undiluted, food grade white vinegar for at least 1 hour, rinses for 5 minutes and cleans the cold water inlet filter, as Rinnai's manual describes.
- Result that matters:
- the LC code clears and the heater runs normally.
- If LC clears:
- keep the date for the next maintenance.
- If LC remains after the flush:
- the professional must complete the LC reset Rinnai describes or call Rinnai technical support.
- Evidence to keep:
- service report with the flush date and the code shown after it.
Rinnai says repairs and maintenance should be done by a licensed professional. The flush needs isolation valves, a pump and hoses on a gas appliance. Do not open the casing.
Evidence: Rinnai USA troubleshooting tankless water heater diagnostic codes · Rinnai Value Series tankless water heater installation and operation manual
Still not solved
If the error persists, stop here. See what the technician must do and show you.
Where this code applies
A code is meaningful only inside the right product and version context.
Primary scope
- System
- Boilers
- Brand
- Rinnai
- Product type
- Tankless gas water heater
Known code variants
- 1 LC
- code erreur LC lave-linge Samsung
- codice LC Samsung
- código LC Rinnai
- erreur LC Samsung
- Error LC
- error LC Rinnai
- Error LE
- errore LC lavatrice Samsung
- Fehlercode LC Samsung
- LC error
- LC0
- LC1
- LC2
- LC3
- LC4
- LC5
- LC6
- LC7
- LC8
- LC9
- LE
- LE error
- LE1
- Rinnai LC
- Rinnai LC code
- Rinnai LC error
- Samsung LC
- Samsung Waschmaschine Fehler LC
What it means
Rinnai uses LC0 to LC9 to show that the heat exchanger is beginning to lime up and must be flushed to prevent damage. Scale comes from hard water at a high set temperature, so water quality, treatment and the set temperature all matter. The number counts temporary restarts made without a flush, and repeated LC codes lock the heater out. In the code history LC appears as 00. The code points to scale, not to a failed part.
Warnings and stop conditions
- Higheditorial warning
Do not rely on temporary restarts. Rinnai says repeated LC codes will eventually lock out the heater and that damage caused by lime build-up is not covered by the warranty.
Evidence: Rinnai Value Series tankless water heater installation and operation manual
- Criticalsource verified
If you smell gas: do not try to light any appliance, do not touch any electrical switch and do not use any phone in the building. Call your gas supplier from a neighbor's phone and follow its instructions; if you cannot reach it, call the fire department.
Evidence: Rinnai Value Series tankless water heater installation and operation manual
Symptoms and causes
Probable causes · in order
- Scale build-up in the heat exchangerConfirmed
This is what Rinnai links to LC. The number after LC counts how many temporary restarts have been made without a flush.
Evidence: Rinnai USA troubleshooting tankless water heater diagnostic codes · Rinnai Value Series tankless water heater installation and operation manual
- Untreated hard water at a high set temperatureCommon
Rinnai says scale is caused by hard water set at a high temperature and that hard water must be treated. It explains why LC comes back after a flush.
Evidence: Rinnai Value Series tankless water heater installation and operation manual
Virtual technician
Does LC still appear after these checks?
Answer a few questions to narrow down the likely cause and the safest next action. Guidance only - it never replaces a professional.
Sources and technical references
- 1
Rinnai USA troubleshooting tankless water heater diagnostic codes
Rinnai America · 2024 · manual
- 2
Rinnai Value Series tankless water heater installation and operation manual
Rinnai America · 2019 · manual
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