Rinnai RL75i error code 14

AndrewS · May 28, 2020

My Rinnai RL75i tankless water heater for error 14 a couple months ago and stopped heating, after some research I found the code meant it was overheating. I flushed the water heater for a couple hours and that seemed to fix my problem until today, error code 14 again. So I went ahead and flushed it for an hour and a half and it worked for a few shower error 14 again then started working again and is currently working. I’d like to fix this issue, I’m thinking it’s probably a blockage in the heat exchanger and the heat exchanged needs replaced since it starts working again I’m assuming a thermal fuse hasn’t blown or anything. Any other thoughts or suggestions?

Jamesplumbing06 · May 29, 2020

Call rinnai tech support. You have a bad sensor or a bird built a nest in the exhaust and is now roasted duck.

check the flame color. Should be 95% blue.

If you live in a dusty area. You could (but not recommended for the novice) clean the heat exchanger and exhaust coils. It’s possible but not easy. Take pictures before and after each set of screws. Use your phone and record if you can’t remember to snap pics. Vacuum the coils out from inlet and outlet.

AndrewS · May 29, 2020

I will check the exhaust and ensure it is clear. It isn't making sense to me because it is so intermittent. For example, last night after flushing it worked momentarily then stopped, then worked for 2 showers then this morning, I used the sink faucet and it worked no problem, but once I turned the shower on it only worked for a few minutes, maybe the sink faucet isn't getting enough water through to overheat it? Normally when I flush the heater I will get some white sediment out, but last night I got nothing out.

I'm definitely no professional, but I do consider myself fairly handy with most things. I'm a little lost when it comes to this tankless unit, as its the first one I've ever had. Does the water heater have to be stripped all the way down to get to the exhaust coils? Also, I assume I could ohm the thermal sensors? I was thinking heat exchanger because last time this happened and I had the cover off, there was some slight discoloration and a long 2 hour flush seemed to fix the issue... until now. What would the best way be to clean the heat exchanger? Soak in vinegar? From what I've seem it just has an inlet and outlet pipe?

I'm just really trying to avoid dropping a bunch of money to have a tech come out - I can only imagine what it would cost.

Jamesplumbing06 · May 29, 2020

Tech support will walk you through and warranty most any part. Your gonna have to talk to them to order the part. Trust me. As a certified tech. I still have to go through troubleshooting with some Egyptian dude typing on a computer. Just be prepared if you don’t have a gas pressure gauge. Read the book. Tell them the number in middle of each range. We know it’s the high temp sensor or flame sensor. Sometimes they send both. But it’s not just a simple diagnoses and go order part. Tell them your a plumber. They don’t verify or ask anymore questions. But you do have to go through the dance

To clean exhaust. Remove front panel. Remove vent. Remove the heater exchanger front access. Need to have 1/4” flame resistant seal. For reassembly. From there you use a shop vac with tiny attachments to clean the soot. Need brush attachment. Gently rub fins. Get air compressor with blower. From the top your gonna blow down the fins. No more than 45 psi. Hold big hose of vacum inside exchanger while sucking with vacumm blow your air into top of exhaust. Keep on till you stop coughing. (Joking get a mask). Reassemble but razor clean old fire seal and use new using same pattern. Be careful of the rubber band seal inside. Don’t break it. You can’t just buy one.

No prying , wedging, besting , tapping. Screws come loose panels come off. Nothing to force apart. Do not bend any of that metal.

You will feel awesome if you succeed. It’s gratifying getting into it that deep. You’ll learn a lot about it. .

AndrewS · May 29, 2020

Thanks for all the info. Flame appears to be 100% blue through the sight glass, no roasted duck. I noticed on the left middle of the heat exchanger it is discolored. I checked it while running hot water with a temperature gun, and the discolored area was around 100 degrees or a little higher while the other areas were 70-80 degrees. Is that normal? It sounds like you’re thinking it’s definitely a sensor, not a blockage in the heat exchanger. Although you said the access panel for the heat exchanger, does it open up for cleaning? Also where is the best place to get a 1/4 fire resistant seal?

Jamesplumbing06 · May 30, 2020

If you got blue flame then your fine. No need to clean exhaust. But .... since you asked. once main cover comes off. You got 8-10 screws holding access cover on combustion chamber and exhaust exchange. They are stacked. It’s the big square box inside unit. I have gotten the seal online a few years back. It’s been awhile. The only time I ordered it I was just like you. Bound and determined to fix it come hell or high water tech support smech support. Who needs em. Ended up repairing nothing. Broke the little rubber ring seal on combustion cover. Had to call tech support. They sent me the new seal and both flame sensor in combustion and temp sensor on exhaust. Customer had to wait 2 days for shipping with no hot water. So good luck. I am one to always find out the truth for myself. Never taking direct advise. So I know what your going through. Tech support will be a necessity.