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Rinnai works intermittently

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ropd
ropd Member Posts: 2
in Domestic Hot Water
I have a 10 year old Rinnai external tankless water heater. For the past month it has intermittently stopped putting out hot water and initially gave me a code 12. I contacted my gas supplier and naturally, when he arrived the next day it was working fine. While here he also checked gas pressure and a few other things. Everything seemed up to spec. About a week later it again stopped working and gave a code 11. Both these codes indicate some type of ignition problem. I pulled out the flame rod and electrode and cleaned them as they did have a light coating of loose corrosion. Put everything back together and it worked fine for a couple more days. Today I get another code 12 and no hot water. What's weird is the problem seems to happen in the morning. Later in the day it begins working again. Although this isn't always the case.

In April the unit was getting no power at all so I had a tech from my gas supplier come out. After getting on the line with Rinnai tech support it was determined the problem was a bad transformer or PC board. After replacing the transformer with no results, I replaced the PC board which solved the problem.

Anyone got any ideas? I've got a new flame rod and electrode on order from Rinnai just in case that's the culprit. I just don't know how much more money I want to sink into a 10 year old unit. If I do replace it I will get a similar unit.

Rich

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  • Slimpickins
    Slimpickins Member Posts: 339
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    If the gas pressures are good, sounds like the burners may have a restriction. They need to be removed and blown out both directions with 120 psi of air pressure. It will be a good idea to replace the flame rod and electrode and gasket as well since you disturbed the gasket. This will need to be done by a professional.
  • ropd
    ropd Member Posts: 2
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    Are you saying the blowing out of the burners should be done by a professional? Is that because of where they are in the unit? I've done pretty good so far replacing the transformer, PC board and removing and replacing the flame rod and electrode, including a new gasket. But if there's something intricate about the cleaning of the burners I'll get a guy out here.

    Thanks for your response.
    Rich

    P.S. - The unit started working again this evening. Maybe it just likes to sleep super late in the mornings. Gotta fix it though.
  • Jack
    Jack Member Posts: 1,047
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    When you replaced the pcb, did you re-set the gas pressures hi and lo? With modulating appliances you need get the board to "recognize (?)" and co-ordinate operation with the gas valve. You may be blowing out the flame if the pressures are off, which will give you the 12. On the 11, the same situation could prevent firing. 12 is flame failure. 11 is fail to ignite. As to am/pm operation...I don't know, maybe air density with different temps if the gas is off? I bet the intermittent operation is also flow volume related, again if the gas if off. A non-condensing 10 yr old unit could use a thorough cleaning. Pull inducer motor and clean wheel/housing. Look above its mounting point and see if the air diffusion plate above is clean. Pull the burners and clean. Swap the 3-4 burners at the flame rod area with the 3-4 on the extreme left of the burner tray. That is only 4 screws to access the individual burners. Flush the unit. Other than the gas pressures, don't get into it until you have all new gaskets. You will need them on the burner and get them for the flame rod/sparker as well.

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