Rheem Tankless Water Heater Not Turning On [7 Easy Fixes]

The leading reasons why your Rheem tankless water heater not turning on include:

• Faulty power supply
• The unit isn’t getting the adequate voltage
• The heater is in maintenance mode.
• Malfunctioning remote control thermostat
• Interruption in gas supply (for gas model)

Besides there might be a failed control board or the overloaded system is causing to trip off the main circuit breaker.

Before considering anything other, find out the tripped circuit breaker and reset it. Or, replace the blown fuse. Above all, ensure an adequate voltage supply to your unit to run it efficiently.

But my years of plumbing experience tell me that it isn’t enough to fix the issue. So, Let me expose what might be amiss with your Rheem tankless water heater with the easiest fixes! Let’s start!!

How You Fix Instantly:

Before digging deeper, let’s make your overall reading easier through the quick table highlighting all the probable reasons for this issue with the instant solutions:

Rheem Tankless Water Heater Not Turning On [Reasons+Solutions]

Well! After previewing the quick fixes, certainly, you are looking for a detailed guide to deeply inspect your Rheem tankless water heater to turn it on. Look no further! We’re here bringing here all for you! Let’s move on!

01. Degradation In Power Supply

If your Rheem tankless water heater is not powering on, the best chances are your unit is going through a major degradation in power supply. If you have an electrically operated Rheem tankless water heater, it requires a fluent electric supply throughout the system to run effectively. 

Even if you have a gas-equipped tankless water heater, it also needs electricity in order to run and regulate. 

If the power has gone out, you never expect to turn on the heater even if there is no interruption in the fuel supply to the unit. 

At times, you may experience a tankless water heater not working after power outages. The power is back up inside the home, but the water heater might fail to work. Whatever the fact is, let’s figure out all the reasons that could be the cause behind the issue:

i) Tripped Circuit Breaker: 

The first reason behind the Rheem tankless water heater no power is the tripped circuit breaker. Unlike other electric appliances in your home, your tankless water heater has certainly a circuit and breaker in the electrical panel. 

It is designed to ensure the proper amount of electric supply to the unit to operate safely and efficiently. 

Now in case the circuit breaker has tripped due to an electrical surge, your tankless water heater won’t turn on at all.

How To Fix:

If the circuit breaker has tripped, simply flip it to the “On” position. 

Also, it’s essential to figure out the reason for it. The most obvious reason is electrical circuit overload. If so,  move plug-in appliances to a less-used circuit to reduce the load on the panel. 

ii) Blown Fuse

If the circuit breaker is not the issue, check to see whether the fuse is in place or not. Your tankless requires two 3A fuses in the line voltage. Chances are the fuse has blown due to overheating.  

Here the heat may be built up by old and loose connections then start to arc that cause the fuse to blow. 

How To Fix:

In case of a blown fuse, you must have to replace it. Make sure you have a certified electrician to wire the new fuse for you. Track down the loose connections into the fuse panel and fix them.  

iii) Cut Or Burnt Out Wiring Connection

If your water heater keeps blowing the fuse and due to that it fails to turn on, be sure you have a faulty wiring connection to the unit. One or two wires of the heater might be shorted, loosely connected, or burnt due to overheating.

Undersize wiring connection is another root culprit that you can’t ignore at all. If you’re keeping the short wires in place, chances are it will mix out and cause the circuit breaker or fuse to constantly trip.

Whatever the fact is, you will never expect to get back your tankless unit into normal function since the wires are damaged.

How To Fix:

Inspect all the wiring to your water heater for any faulty connections.  Figure out where the wires are cut, chewed, or burnt. If so, just replace it ASAP. Make sure the wires are sized correctly for your tankless unit.

Above all, you need to inspect the junction boxes, breaker connections, and fuse connections as well. As the complete task needs enough precautions to perform, it’d better let your plumber deal with the job. 

iv) Faulty Switch Board

At times the problem lies where the water heater is connected. Yes! You get it right! A faulty switchboard is another root culprit for why your electric appliance is not turning on even after a long try. 

As for frequent use, it’s very common for them to wear out. At times, the earthing may not be proper in the box, or it has a loose connection.

How To Fix:

First off, connect another electric appliance to the same wall switch to see if that is working or not. If not, the problem really lies here and needs visual inspection. 

You need to figure out the faulty or damaged wiring in the switchboard. And then, remove the damaged portion to ensure a fluent electric supply to the heater. If the problem continues after the preliminary steps, hire a professional to deal with it. 

v) Plugging Problem

Along with checking the wall switch, don’t miss to examine the power cord condition which through the heater is connected. Chances are the switchboard is all okay but there has a loose or damaged power cord connection. 

All those are the obvious reasons why a Rheem tankless water heater not turning on. 

How To Fix:

Here is all to ensure a snug plug-in of your tankless water heater to the electrical connection:

• Open the plug and tighten all the wires of it. If needed, replace the damaged or worn-out power cord. 
• Avoid using power strips or multiple outlet adapters to connect your water heater. Only use an effective power cord and connect it to a matching grounded electrical outlet. Don’t use GFCI or AFCI circuits for connection. 
• Keep any excess length of the power supply cord on the outside of the water heater.

02. High/Low Voltage 

When fixing the power connection didn’t bring any good luck to me, I headed over to the Rheem technical support and they informed me that a low or high-voltage supply is an additional thing that must be checked out. 

Almost all the models of Rheem tankless water heater require a properly grounded 120 VAC/60 Hz power supply to operate properly. 

In case, if the voltage supply is less than the minimum or higher than the maximum, your heater won’t turn on due to inadequate voltage.

How to Fix:

To resume your water heater functioning normally on its own, you need to make sure of a proper voltage supply to your water. For instance, take a multimeter to check out the voltage amount going through your water heater. 

Here, you can hire a rusted and qualified electrician if you are getting it hard to measure the voltage for your water heater. 

Above all, check out the ON/Off switch for your water heater to see whether it is in well working condition for the incoming 120 VAC power supply.

03. The Heater Is In Maintenance Mode

If your Rheem tankless water heater won’t turn on and all the connection from the power supply is quite fine, be sure your water heater is in maintenance mode.  All the Rheem tankless water heater features a Maintenance Mode chart on the Remote Control. 

If you have the heater in maintenance mode, it won’t power on as it should. To know about the details, you can easily access the mode. Here are the simple steps that you need to follow:

Step #1: Press the power “Off” button on the remote control.

Step #2: Turn off all the water supply to your water heater. 

Step #3: Now hold down the UP and DOWN arrow keys at the same time for 5 seconds.

Step #4: In the meantime, you will hear an audible beep and flashes 1E on the display.

Step #5: Keep pressing the UP and DOWN arrow and you will find all information about the water heater.

Now you will easily activate your water heater while in ongoing Maintenance mode. For instance, do the followings:

• First up, push the power button once.
• Now open all the hot water fixtures.
• The water heater should turn on, illuminating the green light.  

04. Faulty Remote Control Connection

Most of the time, faulty remote control installation to the system is the root culprit for why your Rheem tankless water heater is not responding at all even if there is a snug powering connection. 

There are about 2 root wires in the remote control connection. If it is touching each other, it leads to the fuse keep blowing and shutting off the heater. In such cases, you will even get no power to the remote control as well.

How To Fix:

Unplug your tankless water heater and disconnect the remote control from the wiring terminals. Now figure out the faulty wiring connection of it. 

Verify whether the inside wiring keeps touching itself. If so, simply fixing it will resolve the issue. 

Also, test the wires going into the thermostat with a multimeter to check the continuity. At times, you need to replace the faulty remote control thermostat. But to get a better suggestion, we’d recommend contacting a professional to fix the power issue with the remote. 

05. Malfunctioning Control Board

The control board is referred to the brain of the water heater that controls all inputs and actions during the sequence of operations. In case, the control board is not responding well as it should, it will never expect to turn on your water heater as your command in the remote control.  

Either there has a faulty or damaged wiring connection to the control board or the PCB controller is defective or has completely stopped working.

How To Fix:

Unplug the heater from the power connection and remove the front access panel. Now, inspect the control board overall.  Figure out the damaged wiring connection on the control board and fix it. 

Ensure all the connectors to the control board are secured enough and there is not any single defection. If needed, replace the defective control board with the help of a professional. 

Additional Tips: At times, if there is not sufficient water pressure in your unit, the control board won’t be active, affecting turning on the heater. 

Thus, make sure you have a fluent water flow to the unit. In this case, check out the water shut-off valve to ensure that they are opened all the way. 

If still, the water flow rate is too low, look for a water flow restrictor in the water supply lines and remove it.  

06. Ignition Failure

If your Rheem gas tankless water heater won’t turn on, the interruption in the fuel supply is the root culprit to blame. Along with the electric supply you need to ensure a fluent fuel supply to the unit to ensure its functioning properly. 

For instance, big chances are your unit might be going through out of fuel for why it is not turned on. Either the LP tank is totally empty or the gas supply is being cut off. 

Other major reasons include:

• The gas shut-off valve is not opened all the way
• Insufficient gas pressure 
• Obstruction in the gas supply line

How To Fix:

As for the first step, check out the LP tank to ensure that there is sufficient fuel for ignition. Also, ensure the gas supply is not being cut off for your water heater.

If all is okay, now head to the gas shut-off valve and turn the lever all the way. Inspect the gas supply line for any obstructions and remove it to ensure fluent gas supply. 

When all is done, don’t miss measuring the gas pressure of your water heater with a gas manometer. Go through the manual to learn about the recommended gas pressure for your gas types. 

If the pressure is not at that level, adjust it to turn on the heater and the heating functions.  

07. System Overload

While figuring out the actual reasons why my water heater suddenly turned off and was not getting back again, I looked around and discovered that a few hot water fixtures were simultaneously running. That means my Rheem tankless system was overloading, leading to this issue.  

As a tankless water heater user, I bet the term is not newer to you as well. 

Basically, all the water heater require a minimum flow rate which defines how many hot water fixtures we can run for the unit simultaneously. In case, the hot water demand goes beyond the limit, the unit shuts off and stops the complete heating process. 

If that is so, you may be using too many hot water fixtures at a time and that leads to system overload. 

Do you know, an overloaded system may damage the internal wiring, blow fuses, or even trips the circuit breaker constantly? Whatever the fact is, we’re suggesting some effective fixes to deal with this issue. Here you go! 

How To Fix:

First off, turn off the extra hot water fixtures that you are running.

Now, try to reset the heater unit from the main circuit panel. Simply flip the breaker switch to the “off” position for some time and turn it back on.

Then, plug your heater in again and try to turn on it. 

This time, your Rheem tankless water heater should come on. If not, consult a professional to figure out the deeper reason for this issue. 

You may need to replace your water heater as well. For instance, this time must go through the flow rate capacity of the unit first to ensure that it will meet your household hot water demand.

FAQs:

In Closing

Undoubtedly, Rheem tankless water heater is an excellent product in providing hot water as the user demands. But while operating it, many problems appear in the system that affect the overall performance.

Anyway, if you’re struggling with your Rheem tankless water heater not turning on, it’s an obvious sign that the system needs servicing. But before that, you can try to fix the issue by yourself and for instance how our comprehensive guide is enough to help you out!

Overall, you should always focus on the proper maintenance of your tankless water to overcome such issues in the future. Here we’ve a detailed guide on Rheem tankless water heater maintenance for you describing the effective processes to maintain your water heater.