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My rinnai heater keeps flashing code 12

When my heater tries to maintain the set temperature it shuts down
and flashes code 12

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  • Joshua Sverid
    Joshua Sverid Jan 13, 2009

    for some reason when the heater is on high it will stay on but as soon as it hits room temp it says code 12 and quits    why?

  • Anonymous Jan 21, 2009

    We have the same problem. Heat shuts down and flashes 12, and occasionally shuts down without flashing 12. Normally I can temporarily remedy it by turning off the wall switch that controls power to the Rinnai, and also to the furnace blower, and turn it back on again, basically rebooting it. It is only a temporary fix however.

    Our unit heats our hot water and also a heater coil that is installed in our previous gas forced air furnace duct. The heater coil heats our home.

    One thing I know of is that the system we had installed has its own temperature balancing control. Apparently this conflicts with the standard temperature balancing feature on all the separate faucets and shower. As a result our water temperature is very unstable, especially in winter when the furnace, shower, washing machine, etc. are all demanding hot water. Showers are an adventure...



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SOURCE: rinnai natural gas log fire heater

12 is a fault code, look in the book if you have if, i think 12 is no or low gas pressure, cheers

Posted on Feb 05, 2009

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SOURCE: Rinnai monitor heater 1004F

hope this helps

Posted on Feb 13, 2008

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SOURCE: Rinnai Heater - error message "12"

I fix Toyo's which are related to your heating unit. When a Toyo Laser 30 has an error code of 12, it means that the screen in the back is plugged up with lint, dust, or something causing the unit to over heat. A screen with what appears to be a little fuzz can be a significant clogging of the cooling air passive design of the system. Look for a lint screen and try cleaning it! Also, check out any info is the book about screen filters, fan shrouds etc in case your wording is diffrent. Toyo Tech

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SOURCE: rinnai tankless water heater keeps beeping and showing LC

Time to flush it. LC indicates lime scale build-up.

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I have a Rinnai 556F Heater and I set it to a specific Temperature and a temperature higher is always flashing. What is wrong?

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Error code 12

Three main causes.

Short circuit on the low voltage side of the wiring (12V) This will show as an immeadiate error code 12 befoe the thing even tries to light.

Faulty earth on the low voltage side shows same as above.

A faulty gas regulator or partial blockage of gas supply that allows the unit to fire, but will not maintain sufficient gas supply to keep it alight. This will happen after it has lit, maybe erratically with the occasional error code 11 if you try and re-light immeadiately.

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Do rinnai heaters run efficiently if turned up and down often?

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My Laser 30 keeps getting a ee 12 code ans shuts


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Rinnai heater flashes code 12


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I had the same problem and the heater started working after I cleaned both filters, the bigger one that can easily be taken off and the smaller one that needs to be screwed off.

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