Rinnai RU199i Cycles On/Off then code 12

nsuiter

I have a Rinnai tankless water heater that is about 3.5 years old. It's recently started intermittently throwing a code 12. The failure seems to occur only when showering or occasionally when the kitchen sink is running. I can fill the bathtub and the unit works just fine. I've also tested and found that if I open 2 hot water taps while running the shower, the hot water supply is fine.
I viewed the performance data while running just the shower and it showed a flow rate of 1.1 gal/min which seems to indicate the flow sensor is working ok(?). While just the shower is running the unit's "In Use" light comes on, then cycles off, the flame goes out and the ventilation system kicks on. Then, the light comes on again and the process repeats. Cycles about 3 times before throwing the code.
It sounds to me like maybe this is an issue that only occurs when a moderate amount of water is flowing and the flame is modulating - am I thinking about that correctly? I cleaned the flame rod and igniter and have flushed the heat exchanger. Any ideas what other steps I should take to try fixing this?

Thanks!

Larry Weingarten

Hello, As a start, let's make sure the problem is actually with the heater and not out in the plumbing someplace. So, try this test for crossover. Shut off cold supply to the heater. Open a hot tap. Does water stop flowing after just a few seconds? If not, there is a crossover and cold is leaking into the hot side, reducing flow through your heater and causing, or contributing to the problem. Let us know what you find. Thanks.

Yours, Larry

nsuiter

I knew I was going to forget to mention something - I did a crossover test using those steps a couple days ago and after a few seconds the water does stop flowing so I don't think I have a crossover.

Thanks!

Larry Weingarten

Hi, Here's a rundown of possible problems: https://www.home-water-heater.com/how-to-fix-rinnai-error-code-12.html#:~:text=An error code 12 found on the Rinnai,same error code appears on the remote controller. I don't have hands-on experience with this heater, but maybe others here do.

Yours, Larry

Slimpickins

A code 12 is a lost flame fault code. It sounds like you have a venting issue. Make sure venting is correct and unit not sucking in exhaust gases. I don't think you have a gas press issue since it seems to do it with a lower flow rate, its something to check though.

nsuiter

Took a couple videos of the burner in operation. One where the flame fails and one where it stays lit:

Failure: https://youtu.be/Vq7slCC4w38
Success: https://youtu.be/cbU698GUCuc

not sure if that will help shed any light but thought it might be helpful. I’ll try checking and cleaning up the ventilation soon to see if that fixes it. Thinking I may need to clean the burner also.

Slimpickins

Why don't you post some pics of the venting and termination. The last thing you want to do is clean the burners. It's a big job if you haven't done it before and you need gaskets and o-rings on hand.

mattmia2

Is this one that has a magnetic flow sensor that can get fouled with magnetic particles in the water? Make sure there aren't any strainers in the inlet that are clogged too.

nsuiter

Here’s some pics of the air intake and termination. I can feel airflow from the exhaust termination when the unit is in use and can feel it pulling air when I open the unit up and put my hand near the opening of the noise filter (air intake).

I think the flow sensor on this has a little pinwheel (not sure if it has any magnetic properties). I have cleaned the inlet filter and back-flushed the unit to try to clear any potential obstruction to the flow sensor. It does “feel” like a flow sensor issue since the flame almost immediately cuts off after igniting when there’s low/medium demand.

This is the flow sensor part: https://wwcsupply.com/rinnai-107000269-water-flow-sensor-assembly.html

mattmia2

Sometimes the flow sensor is a magnetic wheel that something like a hall effect sensor outside of the housing senses it rotating and because it is magnetic the wheel can get fouled with ferrous debris in the water.

Slimpickins

It's not a flow sensor problem, it's either a combustion issue. 12 = flame failure. I see you're using room air, is the unit in room with a dryer?
Have you called Rinnai tech support? If not call them and have a digital manometer, multimeter and your hand tools. 

 

JustWantHotWater

First post here. I know this is a really old post. I am not a Rinnai technician. I am just an owner.

What is the heater set to?

I have "heard" that if it is set to 140, the min flow rate for activation moves from 0.4 GPM to 1 GPM as a way for the tankless to protect itself.

You referenced how with the shower it is 1.1 GPM. I wonder if you are hovering around that min flow rate of 1.0 GPM and ultimately the tankless gets confused.

Set the unit to 120 and see what happens.

bganesan

Hi nsuiter, Were you able to fix the issue? We are having exactly the same problem with our Rinnai RUR199iN Model.

brettimby

Hi all, just wanted to share my experience here. I've had a non-condensing Rinnai tankless for a few months now, and every time I used hot water in the washer or filled up my jacuzzi (large water demand for both), the unit would violently vibrate and shake my whole house. Sounded like someone was using a jackhammer downstairs. After monitoring the unit while drawing hot water, I noticed it would vibrate for a while and then the flame would go out slightly after. It would try a few more times to relight, but then it displayed error code 12- no flame.

After doing some digging online, I assumed it would be a vent issue since my gas line was sized properly and there was no issues with leakage or anything else. And sure enough, thinking about it, my big 90-gallon city garbage cans sit on the side of my house, next to the vent. I didn't think the cans would be close enough to the vent to cause an issue, but I decided to move the cans out of the way and try again. And sure enough, I turned on the jacuzzi, and there was no vibration whatsoever- the unit worked as expected.

I will update if anything changes, but I think the cans being so close to the vent was causing some of that exhaust gas to come back in the intake port for combustion, causing an issue with the air/fuel mixture, which caused the unit to shut off the flame as a safety precaution, which then gave me the error code 12. Remember that this is a non-condensing unit, meaning the vent is a pipe-in-a-pipe design, which I don't love for a few reasons but that is another story.

One of my friends has been a plumber his whole life, and he told me that the garbage cans absolutely could cause this issue. He even told me that this could possibly happen if it was very windy or even foggy outside, since the exhaust sometimes isn't able to be pushed out far enough in these conditions.

Additionally, the unit was previously set to 130 but I turned it down to 120 as well. As someone stated above, this could possibly cause issues with the flow rate or even short cycling the burner,

Just wanted to post my two cents here in case anyone else was experiencing this issue. Checking the vent would be my first go-to. Best of luck to all.