Rinnai water heater continually running

It is a Gas Appliance and needs repair by a qualified gas registered technician. It is a generic code for 'no flame'.

energysaver-557ftr-oim.pdf

Rinnai https://rinnai.co.nz > media > energysaver-557ftr-...
Please quote the code displayed when enquiring about service. FAULT. Ignition failure. Flame failure. Overheat. Room overheat. Room Temperature. Sensor faulty.

How to Fix Rinnai Error Code 12 - Troubleshooting Tips

home-water-heater.com https://www.home-water-heater.com > Rinnai
An error code 12 found on the Rinnai tankless water heater means "no flame" or a water heater didn't recognize a flame in the combustion chamber.

Missing: 557ftr ‎' Show results with: 557ftr

Troubleshooting Rinnai gas heater with error code 12.

JustAnswer https://www.justanswer.com > home-improvement > 7...
Jul 10, 2013 - The error 12 is a flame error code. Most customers with this issue ultimately end up replacing the the flame rods to remedy it, ...

1 answer · Top answer: It is pictured for location identification on page 7 of the manual below. CLICK


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No, there isn't an Error 09, but there is a E19.

https://www.tanklesshotwaterguide.ca/about/rinnai-tankless-error-codes/

https://www.google.com/search?q=Rinnai+E110CN+error+E09

...

Sound like "air" is in the system. That will be your cheapest fix before changing parts.
All the Best.

When is the last time it was flushed?

Water heaters are the part of every home in America. The one of the most common reason of that problem is your lithium battery you have used is outdated. Follow these steps to check the problem.

Closed the valve of gas from back end.
open the water heater cover
Replace lithium battery with new one
Screw in the water heater
Check it
Now it will start

Source:
http://www.rinnai.us/documentation/downloads/Owners_Manual_1004.pdf
http://water-heater-installation.net/problems-and-solution-of-rinnai-tankless-water-heater/

Grundfos RCP-96 has Flow range: 0 - 27.5 U.S. GPM
According to Amazon spec sheet:
http://www.amazon.com/Grundfos-RCP-96-UP515-55SFC-Recirculator-Timer/dp/B00128BJAO

Most tankless require .4 GPM to start burner and .25 GPM to maintain burner
Rinnai does not show C85e-1 so you will have to consult your manual to see minimum water flow requirement.
http://www.rinnai.us/tankless-water-heater/
Sample manual from Rainnai mentions 'minimum flow rate' several times but doesn't give specific number. Yet promotion blurb on page 1 says "Ultra operates at a lower minimum flow rate."
http://www.rinnai.us/documentation/downloads/U290-665x0200_Condensing_Manual_EN_FR_1-2010.pdf
Another rinnai manual mentions flow rate several times in troubleshoot section yet fails to define what that rate is:
http://www.rinnai.us/documentation/downloads/U287-1833_VB_Series_R75LSi_R94LSi_R98LSi_Manual_EN_FR_EN_FR.pdf

It might seem that tankless promoters are CTA by failing to mention specific flow rate numbers.
I think tankless promotion is a definite overachiever, and vague flow rate is one tiny example.
It proves the necessity of reading whole manual and asking questions before buying a tankless.
There's another factor to consider:
All performance numbers are based on new products in ideal circumstance, and not based on a 4 year old product located in your home.

Your flow rate may vary, especially over time, and especially if water in your area is not crystal clear, and you are not diligent with correct water softener and filter.
Many factors can affect flow rates: water pressure, number of elbows, clogs in the line, sediment, size of pipe, aireators, water-saving shower heads, local water conservation policies, water well pressure, MUD district pressure issues, your home located near end of a water main, etc.

Read tankless efficiency vrs water softener
http://waterheatertimer.org/Battelle_Final_Report.pdf
Image of tankless parts vrs tank parts
http://waterheatertimer.org/images/Compare-water-heater-parts.jpg
Bradford White tankless vrs tank side by side
Lime scale does not flush out of tankless
Tankless must have water conditions with less than 11 grains hardness
"Savings falls far short of a payback," 'without comparing service costs'
http://www.pmengineer.com/Articles/Cover_Story/8cf9e86f7c298010VgnVCM100000f932a8c0____
Sediment clogs tankless pressure sensor without softener.

make sure the water is not frozen

You need to loosen the inlet water line and see if water is flowing into the unit if it is then on the output side do the same thing if there is no flow get a light bulb and put it inside the unit and cover it for about two ours use a 60 watt light bulb, then try it if you still have no water then I will give you the web page where you can look at the trouble shooting chart for your model which you did not give. Also they have a tech support you can call but you have to register hope this helps and Merry Xmas and a happy new year to you. Thanks for using fix-ya.com
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Run through the basic checks

• Power lead from the heater plugged in a socket turned on.
• Gas on to house
• All valves below heater in on position.
• If they have controllers in the house turn on (key pads marked with Rinnai logo in kitchen or bathrooms usually)

There is a turbine that spins in the heater when a hot tap is run. If the heater has been sat for some time not operating the turbine might have stuck. Run the hot tap and keep it running, using a hammer give the centre pipe connection under the heater a firm hit a few times(not too hard). This might unstick the turbine.