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Rinnai V65IN code 12

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Icarus
Icarus Member Posts: 143
in Domestic Hot Water
Brand new, self installed Rinnai V65IN. (I am not a “authorized Rinnai “ guy, but I have worked on lists of Rinnai water heaters/space heaters/boilers, so I am not completely green)

Installed, and here is the symptom. It won’t come up to full fire, and faults off code 12. If I set the tstat temp to 110,it usually (but not always) hold flame, but at 120f it will shut down. Also there is a 30k BTU Rinnai space heater on the same line. It faults quicker if the space heater is firing. The space heater doesn’t seem to care.

I suspect low gas pressure (I am awaiting a new manometer as I “loaned” my and have never seen it since!), but the pipe sizing should be big enough, ~25’ of 3/4” BI, reduced down to 1/2” for the last 5G to heater. I’ve never had gas supply issues even with significantly undersized gas piping.

I realize that I need to wait and check with the manometer but wonder if anybody has any ideas.

Thanks,

Icarus

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  • Icarus
    Icarus Member Posts: 143
    edited November 2020
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    UP date...I have ~5” WC of gas pressure pre valve. With the manometer on post valve, the valve opens and the heater fires, the meter spikes to ~5” and then drops to effectively zero. There are some instructions on how to adjust the gas pressure setting, in valves dip switches and “calibrating forced high” and calibrating forced low”. Doing the steps as I understand them, makes no difference on the manometer, nor any difference in the flame. Any advice would be appreciated.

    Icarus

    PS. Edit. I found where the pressures are mentioned in the manual, for forced high and forced low, but I am still not clear how it works, especially since the burner fails code 12 before I can get any reading on the meter.
  • Icarus
    Icarus Member Posts: 143
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    Further update. Manipulating the pressure adjustment switches as per instructions has no effect on manometer readings. When you try to force high flame the heater shuts down and immediately faults 12, no flame. As a last resort I will take the burner apart to make sure there is nothing clogging the high flame side. Beyond that, I’m stumped.

    Icarus
  • Slimpickins
    Slimpickins Member Posts: 339
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    The minimum gas pressure on inlet is 4"wc, if it's dropping to zero, you have a regulator or sizing issue. There is no way to check you manifold press if it's dropping below the minimum. The maximum is 10.5"wc and you want to see ideally a 1/2 inch drop is gas is sized correctly
  • Icarus
    Icarus Member Posts: 143
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    Thanks for the help. The issue turned out to be not enough volume. There was one section of 1” pipe, one section of 3/4” pipe and one section of 1/2”. I replaced it all back to the 1” and it works fine. A bit of fine tuning with a digital manometer, and it is fine. A quick note. I have done a ton of gas work, and never had an issue with volume so I never put 2 and 2 together. Most of my piping has been done for LP. Never twigged on the idea that nat gas runs on so much lower pressure (and therefore volume) it is no surprise it didn’t like it. Also Rinnai are smart enough to know that they don’t have enough gas. Most old school appliances simply burned lower.

    Icarus

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