Rheem Tankless Water Heater Error Code 12

Discussion in 'Tankless Water Heater Forum' started by Bill Schleusner, Feb 12, 2019.

  1. Bill Schleusner

    Bill Schleusner New Member

    Joined:
    Feb 12, 2019
    Location:
    Grand Junction, Colorado
    I have a Rheem TWH that's less than 6 months old. I had it installed professionally. I also have a recirc pump hooked up with a timer and aquastadt.

    The WH is now throwing error code 12s all day long. This just started a week ago. I can't get the WH to stop throwing error codes. If the recirc pump runs too long, it throws an error code, if it sits all night turned off and kicks on in the morning, error code.

    Spoke with reps from Rheem and they weren't all that useful other than to request static and dynamic gas pressure readings. I have a plumber coming so he can do readings, but I don't think that's the issue. Why would the gas pressure change in the last week?

    I'm asking this learned group because Rheem doesn't have a "contracting plumber" in Grand Junction and most of the plumbers here are not familiar with tankless units.

    I've done all the diagnostic checks suggested by Rheem and they all check out; voltage to the white and blue molex, flame rod status, etc. The only checks left are gas supply (see above), venting (it's OK) and ground.

    If anyone has any ideas and/or suggestions I'm all ears. I'm at my wits end with this heater.

    Thanks
    Bill
     
  2. plumber69

    plumber69 In the Trades

    Joined:
    Jun 20, 2014
    Location:
    Prince Rupert, British Columbia
    I would clean the flame sensor first. Or maybe you got debris in the gas line filters. Is the gas line copper?
     
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  4. Dana

    Dana In the trades

    Joined:
    Jan 14, 2009
    Location:
    01609
    On a tankless this young it's probably not going to be a dirty flame sensor, though that would be a likely culprit if it were a few years old. It's easy enough to inspect & clean the flame sensor though. Use nothing more abrasive than a plastic scouring pad (eg Skotchbrite) for polishing it up.

    It's most likely to be a gas supply issue, insufficient gas pressure, gas lines too small for the BTU load, unstable pressure from a bad regulator, etc.

    Does it have a dedicated gas line that taps in very close to the gas meter/regulator, or is it off a branch shared by other big burner appliances such as a furnace or boiler?

    Which model Rheem?
     
  5. Bill Schleusner

    Bill Schleusner New Member

    Joined:
    Feb 12, 2019
    Location:
    Grand Junction, Colorado
    It appears to be black steel pipe, not copper for the gas.

    Had a plumber come out and we checked the gas pressure WHILE on the phone with a "senior tech" from Rheem. Pressure checks out
    perfectly, air venting checks out perfectly, neither the plumber or the "senior tech" have a clue as to why this is happening. Water heater is
    less than 6 months old and it continues to throw EC 12 about every 10th fire up.

    I'm not sure how much the recirc pump is adding to the problem. I have an aquastat (85-105) hooked up to the pump and it seems to be working as designed. We (the plumber) increased the water pressure in the house, but I don't see any significant change (good or bad) to the water heater.

    I'd check the flame sensor but I really don't know where to look, besides, as I said, the heater's only 6 months old.

    I'll never buy another Rheem in my lifetime.
     
  6. Bill Schleusner

    Bill Schleusner New Member

    Joined:
    Feb 12, 2019
    Location:
    Grand Junction, Colorado
    It's not a gas pressure issue. Nobody can explain why this just started acting up last week. It worked fine for over 5 months.
    The Rheem "experts" are anything but, basically worthless.

    Would a regulator go out in less than a year?

    https://www.tanklesswaterheaterdepo...kzb9rZLPlJ37dtji-kaA4yK2NohDkWBxoCLooQAvD_BwE

    Here's a picture of the POS. It has a dedicated 3" line each for the intake and exhaust. Both are clear and free of any debris.

    upload_2019-2-17_17-13-51.png
     
  7. Dana

    Dana In the trades

    Joined:
    Jan 14, 2009
    Location:
    01609
    You say it's not a gas pressure issue, but until you've measured it that would not be a good assumption, even if it seemed to be working fine a few weeks ago.

    Was a new gas regulator at the meter installed when the tankless was installed? Do you have a higher pressure gas line inside the house, regulated separately at each gas appliance?

    What diameter & length is the gas line between the tankless & meter, and is it shared by any other appliances?
     
  8. plumber69

    plumber69 In the Trades

    Joined:
    Jun 20, 2014
    Location:
    Prince Rupert, British Columbia
    What other gas appliances do you have. Could still be gas pressure. Could be only happening when multiple gas appliances are being used at same time. And did he test it right. You would want to test it running mulitple taps
     
  9. Tankless Tech

    Tankless Tech New Member

    Joined:
    Jun 12, 2019
    Location:
    North Little Rock, Arkansas
    Like dana said you cant be sure it isnt gas issue until readings have been taken. if the gas supply was too low but still burning what could happen is the flame sensor(s) are coated with a layer of soot. when the gas burns at incorrect ratios it doesnt all burn at the rate it should and can in a matter of weeks turn a new unit into a code throwing nightmare. and when the help you have available isnt aware of the possible problems you get frustrated and make assumptions. those flame sensors are sensitive and cleaning them can temporarily fix your problem but with the speed that it came up on you theres something else causing the issue. are there lots of bugs in your area and have you taken the burner assembly out and inspected for trash that came through venting / combustion air intake? are there screens installed on your vent termination? how far is the unit vented? how many bends? there are so many factors you have to consider before you can say rheem is a bad product. these units are high tech and requiring planning before install. in my area the "proffessionals" arent pros with tankless they are however very experienced plumbers who just dont know about what has to go into a tankless install. venting may be "ok" but is it really?
     
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