Rheem tankless water heater code 11 mainly indicates a fault with the ignition system or the unit is running through with no ignition. This code would pop up due to any of the following reasons:
- Interruption in the gas supply
- Dirty or defective igniter coil
- Flame rod issues
- Blocked or incorrect vent installation
To resolve the issue, you have to inspect the igniter and flame rod first for loose or faulty connections. Additionally, confirm that there is a sufficient gas supply in the system. Plus, clean the obstructed venting to ensure proper ignition.
However, if the issue still persists after your efforts, I bet any of the following villains can be responsible for this error code:
- A malfunctioning gas control valve
- Clogged main burner
- Faulty PCB
Don’t worry! I will expose all the reasons when there is no ignition in the unit, followed by error code 11 & how to fix that trouble based on my personal experience. Hold on tight with me…
Table of Contents
Rheem Tankless Water Heater Code 11 [Quick Overview]
Before getting gist of the issue, here is a quick table for you, highlighting all the probable reasons for the error code 11 on Rheem tankless water heater with an effective fix:
| Probable Reasons | Recommended Fix |
| Inadequate gas supply | #Ensure the gas type, gas pressure and gas pipe size is correct for your water heater. #If needed, purge the air from the gas line. #Make sure the gas shut-off valves are opened all the way. |
| Improper venting | #Clean out all the obstructions from the exhausts and air intake. #Make sure the venting installation is meeting all the requirements of the manufacturers. |
| Spark is not visible | #Verify a good ground connection of the igniter. #Replace the defective igniter coil. |
| Faulty flame rod | #Test the flame rod wiring harness to the control board. #Replace the bad one. |
| Defective main burner | #Replace the faulty burner |
| Malfunctioning gas control valve | #Replace the bad control valve |
| Faulty control board | #Replace the faulty control board. |
How to Fix Rheem Tankless Water Heater Code 11? [Easy Solutions]
Well! After previewing the above quick overview, certainly, now you come to know that the code can be a bit of a tricky to diagnose as there are lots of different causes.
But don’t get in trouble! Let me walk you through the step–by–step instructions in detail to resolve all the responsive factors for error code 11 on Rheem tankless water heater:
1. Inadequate Gas supply
Code 11 is one of the most frequent errors that may arise in Rheem tankless water heater, signaling an issue with ignition. Now, in case of ignition failure, inadequate gas supply is the first culprit to blame.
Even if you have a gas-operated tankless water heater, a proper gas supply is the key to the efficient operation of the unit.
Now if there is a gas supply interruption in the system, a few factors would be responsible here. Like:
- Using the wrong type of gas
- Inadequate gas pressure
- Improper sizes of gas pipe and flex line
- Air in the gas line
- Gas shut-off valves are not fully opened
- Or obstruction in the gas line
How To Fix:
Start by inspecting the fuel source running through the system. The best chances are you’re using the wrong type of fuel. If so, go through the manual and use the right fuel for your unit.
Inspect your propane tank and make sure there is enough gas in the tank. Now ensure the absolute gas pressure to your tankless unit. For instance, take a pressure gauge and test the gas pressure on your water heater.
If there is any malfunction, adjust the gas pressure for your fuel type by following the chart below:
| Gas type | Maximum pressure | Minimum pressure |
| Natural gas | 10.5” w.c | 4.0” w.c |
| LP gas | 14.0” w.c | 8.0” w.c |
When done, inspect the gas pipe and flex line. Check for any stuck debris on the gas line and regulator. If so, remove it. If you’re suspecting air in the gas line, bleed all the air from the lines.
Plus, make sure that the flex line is in the proper diameter and following the correct BTU rating. Also, it should not exceed 36” in length.
Finally, head to the gas shut-off valves for your unit and open them completely. The gas handle should be perpendicular to the gas line.
2. Improper Venting
Insufficient airflow is another major reason for improper ignition in a gas tankless water heater. Without adequate venting, the combustion gas will fail to escape and the fresh air doesn’t enter into the system.
Now when there is not sufficient oxygen supply in the unit, interruption in the ignition is quite obvious.
In case of poor airflow, the best chances are the air intake & vents are blocked with debris. Plus, you might be not using the correct material, pipe thickness, and configuration for proper ventilation.
Also, if venting is not sealed properly, it can result in exhaust gases ending up re-entering the system and leads to ignition failure.
How To Fix:
Start by inspecting the intake and exhaust venting of your Rheem tankless water heater for any possible blockage or recirculation of exhaust. Take a vacuum clear and remove the stuck debris to supply oxygen to the burner for proper ignition. If needed, use a duct cleaner to clean the part that is hard to reach.
Besides cleaning, go through the manual to see whether the venting material, venting termination and length is meeting all installation requirements. Use stainless steel concrete venting for mid-efficiency indoor installation.
If you have a high-efficiency indoor model, make sure you are using vents on PVC, CPVC, ABS, or Stainless steel. Also, ensure all the vents are sealed properly.
Note: You should inspect the venting of your tankless water heater annually by a qualified service technician to ensure all of the vent sections are secure and airtight.
3. Igniter Rod Not Sparking
If there is no ignition in your Rheem tankless water heater, a higher possibility is that there is some malfunction in creating a spark in the system. For instance, you might have a defective ignitor.
In some cases, if the igniter is clogged with shoots and debris or doesn’t have enough voltage on initiation, it won’t work as it should. Or the igniter might be defective at all by wear & tear.
If so, replacing the bad igniter will only be the one solution to clear error code 11 on your Rheem tankless water heater. But before that, it’ll be worth it to inspect and test the igniter electrically. Here’s all how you do it:
How To Fix:
Before handling the inside parts of the heater, always unplug it from the power connection. Now remove the front cover panel on your tankless water heater by disconnecting all the screws.
- Access the control board and locate the “H” connector on the board. Take a voltmeter and Check AC Volts across 2 grey wires on connector “H”.
- It should give the reading 108 – 132 Volts AC. If not, be sure the control board is defective and needs replacement.
In case the voltage is Ok, remove the white Molex connector at the igniter coil mounted on the right side of the unit. While the unit is attempting to ignite, hold the end of the igniter coil cable 1/8” from the end of the igniter rod. Be cautious that you are holding cable on the rubber insulation while performing this check.
If you are noticing a spark arc across the igniter coil cable and igniter rod, remove the rod and clean it properly. If needed, replace the cracked igniter coil to allow the heater to operate again.
To get better knowledge on Rheem tankless water heater igniter location and how to replace it, you may follow this effective video:
4. Clogged Flame Rod
Flame rod malfunction is another big culprit if you have code 11 Rheem tankless water heater on the remote display. Best chances are there is no flame in the unit or the flame isn’t touching the rod. To confirm the fact, look through the sight glass and check for the flame.
If you can’t see any flame, either there are loose connections around the flame rod or dark carbon deposits have clogged it up. All you need to do is to remove the flame rod from the connection and inspect it to check the status.
How To Fix:
First off, you’ll need to test the flame rod wiring connection to the control board. Locate the white connector “M” and blue connector “T” on the board. Remove the connection and cycle the unit ON.
Now check the voltage at the connection and it should give a reading of 1 – 100 AC volts.
If not, inspect the flame rod for any foreign debris and clean it properly with steel wool. Avoid using sandpaper for better cleaning.
Anyway, after cleaning, visually check the rod for any cracks and damages. If so, replace the bad flame rod. Then attempt to operate the unit again and the error code 11 on your remote display should be cleared.
5. Malfunctioning Gas Control Valve
After confirming all the above troubleshooting steps and still, there is the same error code 11 on the remote display, be sure the faulty gas control valve is the next suspect to check.
If the gas control valve doesn’t operate accurately, the igniter rod will fail to create the spark, and the main burner doesn’t ignite that results in an 11-code error on the remote display.
Anyway, you need to test the solenoid valve electrically to have proper voltage. And then we’ll head to replacement if needed.
Here is the complete diagnostic process of the gas control valve:
How To Fix:
First off, turn off the power supply to your water heater. Remove the front access panel by disconnecting the screws and access the control board. Now, locate the PGFR valve on the lower right of the unit. Remove the Molex connector with red wire and Molex connector with black wire on PGFR.
Check the connections and reinsert it. Then, attempt to operate the unit again. If still there is the same error code on the display, continue to test the gas control valve connection with the control board as follows:
- First off, locate the connector “K” & “R” on the control board. Remove the connection and reinsert them again.
Turn the cycle on and measure the voltage across red wire #1 and black wire #2 on connector “R”. It should give a reading between 1.5 – 14 DC VOLTS.
- Next, remove the Molex connector “R” and measure the voltage reading at the red wire #1 and black wire #2 on Molex connector “R. Here, you will get the resistance reading at 40 – 80 Ohms.
- After that, remove the Molex connector “K” to measure resistance. Measure resistance across black wire #6 and yellow wire #1 on Molex connector “K. The reading should be between 0.8k – 2.4k Ohms.
- Measure resistance across black wire #6 and white wire #2 on connector “K for the voltage reading 0.8k – 2.4k Ohms.
- Also, take the voltage output across black wire #6 with the grey wire #3, red wire #5 & blue wire #4 on connector “K”. In every test, you should get a reading of 0.8k – 2.4k Ohms.
If there is any malfunction on any of the readings above, consider the gas control valve is defective and needs replacement. It’ll be better to call a professional to do this task for you.
6. Non-operational Control Board
In case you are getting all the operations fine from the gas control valve assembly, you need to test the control board now, considering the fault relies here. Test the control board as follows:
How To Fix:
Note: All the voltage checks must be performed while the unit is attempting to go to the main burner and the Molex connector “K” IS connected to the main control board.
Take your voltage meter and measure DC voltage across black wire #6 and yellow wire #1 on connector “K”. It should give the reading in between 90 – 120 DC Volts.
Same as, measure DC voltage across black wire #6 with white wire #2, grey wire #3, red wire #5, and blue wire #4 on connector “K”. At every test, you should get the reading 90 – 120 DC Volts. If not, replace the bad control board.
7. Defective Main Burner
In case you notice that the main burner ignites and shuts off after short ignition, be sure you have a faulty main burner. Either the main burner is clogged with carbon deposits or defective which is responsive to this error appearing.
How To Fix:
Visually inspect the main burner for any damage. You need to remove the burner cover and access the burner assembly. Check inside the burner chamber for any foreign material blocking flame at flame rod. If so, clean it with a vacuum cleaner. If needed, replace the defective burner assembly.
How to Clear Error Code 11 On Rheem Tankless Water Heater?
Well! When you’ve ensured all the above troubleshooting steps to diagnose the Rheem code 11 tankless water heater, follow the below instructions to clear the code from the remote display:
Step #1: Start by turning off all the hot water faucets for your water heater.
Step #2: Also turn off your tankless water heater by pressing the POWER ON/OFF button on the remote control.
Step #3: Wait for 5-10 minutes and turn the back On again by pressing the POWER ON/OFF button.
Step #4: Turn on a hot water heater and head to the remote display to check for the code. This will reset your Rheem tankless water heater. Also, the error code should be cleared from the display. If still, the error code remains on the display, call for Rheem service assistance.
FAQs:
How to check igniter on Rheem tankless water heater?
First off, inspect the igniter for any accumulated debris. Take a steel wool and clean it properly. Also check the voltage across the igniter connector wires to the control board. If needed, you will have to replace the bad igniter.
How to activate maintenance mode on a Rheem tankless water heater remote display?
Turn off the electric and water supply to the unit. Hold down the UP and DOWN buttons simultaneously for 5 seconds. You will hear an audible beep with the code 1E. Keep pressing the button and you’ll access the maintenance mode.
Why is my Rheem tankless water heater not turning on?
If your Rheem tankless water is not powering on, check for a tripped circuit breaker. If so, reset it. Also, you may have a defective remote thermostat or failed control board. If the system is overloaded, turn off some of the hot water fixtures.
In Closing!
The Rheem tankless water heater code 11 is a diagnostic error from the controller that tells there is something in the ignition system of the unit. Several factors can contribute to an ignition failure, starting from insufficient fuel supply, improper combustion, defective igniter coil, flame rod, or gas control valve.
Throughout our comprehensive guide, we have listed a troubleshooting process to assist you in narrowing down where the error code is coming from. Though if you’re not professional, our detailed troubleshooting will be enough for you to guide you on the right path.
Also it’s not surprising that you may encounter error code 12 on the digital display at the same time while in Rheem tankless water heater error code 11 fix. If so, you can check out the effective guide of Rheem tankless water heater code 12 to get all the simplest fixes.