Bosch Tankless Water Heater Troubleshooting [Gas & Electric]

There could be issues with Bosch tankless water heaters occasionally. Here are some common Bosch tankless water heater troubleshooting for both gas and electric:

Gas Tankless Water Heater:

• The water is not hot enough.
• Low water pressure.
• Error codes
• Loud noises
• The water is too hot, etc.

Electric Tankless Water Heater:

• The Neon light does not turn on when only cold water is running.
• The water is not sufficiently hot.
• The water temperature is excessively high.
• The water temperature fluctuates, etc.

Also, there are internal and external issues like incorrect gas pressure, abnormal temperature at the tap, displaying error codes, etc. In this article, I’ll provide an overview of most of the common Bosch tankless water heater issues and offer troubleshooting tips to help you identify and resolve them.

Quick Troubleshooting Tips (Bosch Gas Tankless Water Heater)

Quick Troubleshooting Tips (Bosch Electric Tankless Water Heater)

Bosch Tankless Water Heater Troubleshooting Guide

If your bosch tankless water heater is not working, there are several potential reasons for the problem. Common culprits include a tripped breaker, an incorrect temperature setting, a dirty filter or inlet, insufficient gas or water flow, a faulty control unit or sensor, and mineral buildup.

By following these troubleshooting steps, you can keep your Bosch tankless water heater running smoothly and efficiently for years to come. I’ve kept different sections for both gas and electric troubleshooting guides below. Scroll down…

Bosch Gas Tankless Water Heater Troubleshooting

Here’s a detailed view of gas tankless water heater troubleshooting:  

01. Water Heater Won’t Ignite Burner

There are several possible causes for a water heater burner failing to ignite when the hot water is turned on. They are:

1. Blank display indicating a power supply problem.
2. Wire connection issues, such as loose or damaged wires.
3. Faulty fuses or tripped circuit breakers interrupt the power supply.
4. Incorrect cold water inlet connection or blockages in the connection.
5. Insufficient hot water demand below the minimum flow rate requirement.
6. Clogged inlet filter screens restrict water flow.
7. Obstructions or blockages in the water path within the water heater.
8. Plumbing crossover, causes hot and cold water to mix improperly.

How To Fix:

To restore the ignition of a tankless water heater, you can take several steps. Start by checking the power supply, ensuring the outlet has the correct voltage and the heater is receiving power. Inspect the wire connections and remove the front cover to examine the connections between the water valve, control unit, and electrode set.

Verify the fuses in the control board and replace any faulty ones. Confirm that the cold water inlet is correctly connected to the heater, as improper plumbing can disrupt its functioning. Check the minimum hot water demand, making sure the flow rate meets the required threshold.

Cleaning the inlet filter screen is essential to remove debris or sediment buildup that can block water flow. Rinse the filter screen and reinsert it properly. Inspect the water path for any obstructions, ensuring shower heads, faucet aerators, and whole house filters are clear.

Perform a plumbing crossover check by shutting off the cold water supply and opening all hot water taps. If there is continuous water flow, consult a professional plumber to address the crossover issue.

By following these solutions, you can address common problems that prevent the ignition of a tankless water heater. However, the burner ignition problem can be a serious problem to troubleshoot. Therefore, I recommend you check out our guide on ignition failure of Bosch tankless water heater for more detailed information about the issue.

02. Noisy Burner

Your water heater may emit a high-pitch or low-pitch sound due to various reasons. The reasons are noted below:

• Incorrect gas type selected
• Gas pressure outside the specified range
• Gas and air mixture imbalance 
• Insecurely fastened cover
• Improperly sealed exhaust vent adaptor 
• Improper venting
• Lack of adequate combustion air
• Cross-contamination between intake and exhaust
• Lack of gas pressure
• Improper CO (carbon monoxide) readings

How To Fix:

To resolve the issue related to gas type mismatch, the first step is to check the type of gas you are using. For example, if your tankless water heater is designed to operate on natural gas, using propane or any other gas can lead to dangerous situations. So, it is crucial to confirm that you are using the proper gas type that the manufacturer has specified.

Another critical aspect to consider is the gas pressure. If the gas pressure is too low or too high, it can adversely impact the unit’s performance. It is essential to verify and ensure that the gas pressure is within the recommended range to maintain optimal functioning.

To ensure optimal combustion and performance, it is essential to perform the necessary gas and air mixture adjustments as specified in the manufacturer’s manual.

For this adjustment ensure the gas pressure is within the recommended range. For natural gas (NG) heaters, the ideal gas pressure is typically around a 3.5-inch water column (WC). On the other hand, liquid propane gas (LPG) heaters require a higher gas pressure, usually around 8 inches WC.

To prevent operational issues, it is crucial to fasten the cover of the water heater securely. Make sure the combustion cover is securely fastened to avoid burner noises.

The exhaust vent adaptor should be properly sealed using the supplied gasket. Leaky seals can result in improper combustion emissions and noise. By ensuring a tight seal, you promote effective venting and minimize potential problems associated with combustion by-products.

Venting the water heater in accordance with the specified requirements is essential for proper combustion and overall performance. Following the venting guidelines outlined in the manual ensures that combustion gases are safely and efficiently expelled, preventing any adverse effects on the unit’s operation.

Insufficient combustion of air can disrupt proper combustion and lead to noise issues. So, it is important to provide the water heater with the recommended amount of combustion air as specified in the manual.

Preventing cross-contamination between the intake and exhaust terminations is crucial for stable burner flames and noise reduction. Maintaining proper clearances, ensuring that the intake and exhaust remain separate, allowing for optimal combustion, and minimizing any adverse effects on performance.

Verifying proper carbon monoxide (CO) readings is crucial for safety and efficient operation. It is essential to have a certified gas technician use a calibrated combustion gas analyzer to measure and confirm CO levels. This ensures that the levels of CO emissions are within acceptable limits, promoting a safe environment and optimal performance.

03. Burner Ignition Without Hot Water Flow

If the burners of your Bosch tankless water heater ignite without hot water flow, there could be a few possible causes. One potential issue is a dirty or sticking water valve that prevents it from fully closing the gas valve. Over time, sediment or debris can accumulate in the water valve, affecting its functionality.

How To Fix:

To resolve this issue, the water valve needs to be periodically serviced. You can follow this Bosch tankless water heater maintenance guide to learn more about lubricating this valve. Also, it is recommended to service the water valve every 2-5 years. 

04. Burner Operation Problem: Burners Operating with Yellow Flames

The burner will not operate efficiently if any of the following problems occur:

• The gas type indicated on the rating sticker does not coincide with the gas type being used.
• Inadequate gas pressure, resulting in improper combustion.
• The inlet gas pressure is not set correctly for proper combustion at high elevations.
• Inadequate ventilation, resulting in insufficient combustion air supply.
• Improper water heater venting.
• Dirty or obstructed burners and heat exchangers.

How To Fix:

Ensure that the correct gas type is being used according to the rating sticker. If the gas type is incorrect, switch to the appropriate gas type (natural gas or liquid propane) to ensure proper combustion. 

Ensure the gas pressure is in accordance with the manufacturer’s specifications. A gas pressure reading is needed to proceed further. If the gas pressure is found to be inadequate, it needs to be adjusted to meet the manufacturer’s specifications for proper combustion. 

For proper combustion at high elevations, the inlet gas pressure should be set at installation to the value shown in the below table:

Check the manufacturer’s specifications for proper ventilation requirements and ensure that adequate combustion air is being supplied to the water heater. Plus, ensure the water heater is vented correctly according to the manufacturer’s specifications.

If the burners exhibit yellow or orange flames, it is crucial to clean them to ensure proper combustion. Remove the burners from the unit and clean them thoroughly. Additionally, access and clean the fins at the top of the heat exchanger. Regular maintenance and cleaning will help the burners operate efficiently and maintain clean combustion.

05. Error Codes C1, C2, CF, CE, EA And EC

Bosch tankless water heaters come with built-in diagnostic tools that help identify and display error codes in the event of a malfunction. These error codes are important for troubleshooting and diagnosing issues that may arise with the unit. Understanding the meaning of each error code can help you identify the problem and potentially resolve it yourself. 

Two common error codes in Bosch tankless water heaters are C1 and EA. The C1 error is often caused by an obstruction in the venting system. On the other hand, the EA error is linked to problems with the combustion process. That is typically brought on by inadequate gas supply conditions. Incorrect gas pressure or composition can lead to an imbalanced fuel-to-air mixture, triggering this error.

But there are other error codes like C2, CF, CE, EC, etc. that can trigger in your water heater. You can follow our guide on Bosch tankless water error codes to learn more about them.

How To Fix:

To troubleshoot the C1 error, you can remove any obstructions found to ensure proper airflow and exhaust. Clean or replace the air filter to improve ventilation. Also, to solve the EA error, you will need to verify that the correct gas type is selected for the water heater.

Check the gas pressure and ensure it falls within the specified range. If the gas pressure is incorrect, consult a professional to adjust it. Perform a gas and air adjustment as described in the manual to optimize the combustion process.

06. Fluctuations Of Temperature At The Faucet

Several factors can cause fluctuations in the hot water temperature at the faucet, including:

i) Deactivation due to high water heater set point temperature:

The water heater may become inoperable if the water heater’s set point temperature is set too high or if too much cold water is mixed in at the faucet. 

This is because the excessive amount of cold water overpowers the hot water flow from the tankless water heater. That causes the flow to drop below the activation point. As a result, the burner of the water heater will shut off.

ii) Unbalanced pressure in water lines:

The problem of unbalanced pressure in water lines can occur when there is a restriction in the water heater, such as a clogged inlet water filter screen. This restriction can lead to unequal pressures between the cold and hot water lines. 

As a result, when mixing higher-pressure cold water at the tap, the lower-pressure hot water can be overpowered. This imbalance in pressure can cause the burners of the water heater to shut down. As the hot water flow rate falls below the minimum flow rate required for activation.

iii) Deactivation caused by temperature-balancing shower valves:

The problem of water heater deactivation can occur when using temperature-balancing shower valves. If the set point temperature is too high, the temperature-balancing shower valve will automatically mix in cold water to reduce the hot water temperature. 

This mixing of cold water can deactivate the water heater. The temperature balance valve overrides the hot water flow by introducing more cold water into the mix. As a result, the water heater may not reach the required flow rate and shut off its burners. That can lead to a decrease in the hot water supply.

iv) Erratic inlet water pressure due to fluctuating supply water pressure:

Fluctuations in the supply water pressure can impact the inlet water pressure to the water heater. Rapid changes in the inlet pressure can lead to temperature fluctuations at the faucet.

How To Fix:

First, the solution to this problem is to adjust the water heater set point temperature to an appropriate level. Lowering the set point temperature can prevent the water heater from deactivating when cold water is added during mixing at the faucet.

Secondly, verify and ensure that the inlet water filter screen is clean and clear of debris.

Cleaning the filter screen will help remove any obstructions and ensure smooth water flow. This will prevent the higher-pressure cold water from overpowering the lower-pressure hot water. Also, it allows the water heater to maintain proper operation and prevents the burners from shutting down.

Thirdly, if your tankless water heater deactivates due to temperature-balancing shower valves, it may be related to the set point temperature being too high. These shower valves mix in cold water to reduce the hot water temperature. 

Consider making changes to reduce the amount of cold water that the valve adds to the system to address this. Additionally, lowering the temperature setting on the water heater itself can help reduce the amount of cold water mixed in by the temperature-balancing shower valve. Finding the right balance will help maintain a more consistent hot water temperature.

Finally, fluctuating supply water pressure can cause erratic inlet water pressure for your tankless water heater, leading to temperature fluctuations. If you are using a private well system with a pressure tank, it’s recommended to maintain a constant water pressure within the range of 30 – 45 psi (2.06 – 3.1 bar). 

To achieve this, it is advisable to consult an installer or local plumber who can help determine effective methods for maintaining consistent water pressure in your system. By stabilizing the inlet water pressure, you can minimize temperature fluctuations and ensure a more reliable hot water supply.

7. Water Is Not Hot Enough

When your Bosch tankless water heater is not producing hot enough water, there could be several possible causes that you should investigate. Here are the problems highlighted:

1. The selected temperature on the unit is lower than desired. 
2. The gas type of the heater might not match the gas being supplied. 
3. The inlet gas particle screen/filter could be blocked. If it’s blocked, it can restrict the flow of gas and affect the water heater’s ability to produce hot water.
4. A plumbing crossover might be occurring, leading to a cooler water temperature than desired. A plumbing crossover refers to the mixing of hot and cold water in the plumbing system, resulting in a lower hot water temperature at the faucet. 

How To Fix:

To address excessive hot water output in a Bosch tankless water heater, you can increase the set temperature by using the up arrow until the desired temperature is displayed. 

It’s important to check the rating plate to ensure the correct gas type is being supplied and that the gas pressure meets specifications. 

Additionally, inspect the gas valve and inlet gas particle screen for any blockage or debris that could affect gas flow. 

To determine if a plumbing crossover is occurring, shut off the cold water supply and open all hot water taps served by the heater. If there is continuous water flow, it indicates a crossover issue that requires professional plumber assistance. After waiting for 10 minutes, check for any water flow from the taps. 

You can read our dedicated troubleshooting guide on why Bosch tankless water heater isn’t hot enough to learn more in detail.

8. Water Getting Too Hot

Excessively hot water output in a Bosch Tankless Water Heater can be attributed to several possible causes. 

One common reason is setting the temperature of the unit too high. If the temperature setting is set higher than necessary, it can result in getting water that’s too hot.

Another potential cause is mineral scale buildup within the water heater. Over time, mineral deposits can accumulate and coat the heating elements, leading to inefficient heat transfer and hotter water output. Plus, using the incorrect gas type can lead to improper combustion and higher water temperature.

Obstructions in the water path, such as clogged filters or sediment buildup, can also affect the water temperature. These obstructions can restrict water flow and interfere with the heating process, resulting in hotter water output. 

If you are experiencing excessively hot water output from your Bosch Tankless Water Heater, it is recommended to address these potential causes. 

How To Fix:

To address excessive hot water output in a Bosch tankless water heater, start by checking the set temperature. Press the down arrow to lower it if it’s too high until the desired temperature is shown. 

Descaling is particularly important for Bosch tankless water heaters. To learn how to descale, you can have a look at Bosch tankless water heater maintenance guide that is linked above in burner ignition without hot water flow section.

Ensure the correct gas type is being used in your water heater according to the rating plate.

Check for blockages in shower heads, the inlet filter screens, and faucet aerators and remove them. Also, ensure that preheated water or recirculation applications are not being used, and increase water flow where possible. Replace low-flow shower heads and faucet aerators with higher ones if necessary.

9. Water Flow Is Low

Different factors may contribute to decreased water pressure or flow from your water heater. For instance, using too many hot water applications simultaneously. The Bosch Gas Tankless Unit can efficiently support simultaneous usage of 2 to 2.5 GPM showerheads or multiple sink applications. 

Also, to ensure the proper flow of water, it is important to verify that the gas pressure is in accordance with the specifications. Similarly, dirty inlet filter screens or obstructions in the water paths can also lead to reduced water flow or pressure.

There will be low water flow if the selected temperature on the water heater unit is set too high for the demanded flow rate. Lastly, the mineral scale buildup in the unit can also cause the low water pressure problem.

How To Fix:

To prevent the unit from exceeding its capacity, it is recommended to run fewer appliances when operating the water heater. 

To ensure proper flow of water, you have to lower the selected temperature. That will allow the motorized water valve to open up, resulting in an increased water flow rate. This adjustment will help achieve the desired temperature while maintaining an adequate flow rate.

Contact the original installer or a certified gas technician to obtain a gas pressure reading. If the gas pressure is inadequate, the water heater will close its motorized water valve, leading to a reduced hot water flow rate. This is done in an attempt to reach the selected output temperature.

Check out our dedicated guide on why Bosch tankless water heater is not heating water that is linked above at water is not hot enough section & know how to measure gas pressure.

A dirty inlet filter screen can also cause a reduction in water flow. The input filter screen has to be cleaned if you want the water pressure to be higher. Start by locating the inlet filter screen at the cold water connection on top of the water heater. 

The water should then be purged using discharge drains once the installer-supplied water shut-off valve has been turned off. Remove the brass hex cap holding the filter in place, wash the inlet filter screen with water, and then replace the cap.

The amount of water that flows through the device may also be reduced by obstructions in the water routes. The reasons can be filter screens, showerheads, and faucet aerators. Therefore, it is essential to inspect the water pathways and make sure they are unblocked.

10. Incorrect Manifold Gas Pressure

The manifold gas pressure refers to the pressure of the gas supplied to the burner manifold of a gas appliance, such as a water heater. It is an important parameter that needs to be within the specified range to ensure proper combustion and efficient operation of the appliance.

When the manifold gas pressure of a tankless water heater is not within the specified range, it can result in various problems, including:

i) Inefficient or inadequate heating:

If the manifold gas pressure is too low, the burner may not receive enough gas to produce sufficient heat. This can lead to inadequate heating of the water, resulting in lower water temperatures or fluctuations in the hot water supply.

ii) Malfunctioning or irregular operation:

When the manifold gas pressure deviates from the specified range, it can cause the water heater to operate erratically or inconsistently. 

iii) Safety hazards:

Operating the water heater with gas pressure outside the recommended range can pose safety risks. If the pressure is too high, it can increase the likelihood of gas leaks, which can be a fire hazard or lead to other safety incidents.

How To Fix:

The procedure is outlined for measuring the manifold gas pressure on a tankless water heater and making adjustments if necessary. Here are the steps involved:

Step 1: Turn off the appliance and remove the front cover while keeping the wire connected to the HMI (display) intact. Loosen the set screw of the pressure head point [B] and connect the pressure gauge’s “+” connection to the test point [B]. This measures the gas pressure at the burner.

Step 2: Loosen the set screw of the pressure head point [A] and connect the pressure gauge’s “-” connection to the pressure head point [A]. This measures the air pressure inside the box.

Step 3: Turn on the appliance and position the front cover near the appliance so that the display cable can be connected. Place the front cover with the HMI near the appliance. Open all hot water taps to achieve a flow rate of at least 6 gallons per minute.

Step 4: Ensure sufficient flow by opening more hot water fixtures if needed. This step allows access to the P1 menu. Record the manifold gas pressure reading, which represents the relative pressure between the gas manifold nozzle’s inlet and outlet.

Step 5: Turn off the appliance and disconnect the pressure gauges from the pressure head points [A] and [B]. Tighten the shutter screws of the pressure head points [A] and [B]. Reassemble the front cover onto the appliance. Turn on the appliance to return to normal operation.

11. Pilot Light Issues

To solve the pilot light issues, you have to know about the culprits that are causing the problems. Here are the possible pilot light issues and their reasons:

Pilot light doesn’t light:

• Gas supply is not turned on.
• Air is in the gas line.
• Ignition system is not working properly.
• Pilot assembly is blocked.

Pilot light turns off during or after hot water use:

• Water entering the heater is preheated.
• The Ventilation system is not working properly.
• Insufficient combustion air.
• Delayed burner shutdown.
• Faulty connections in the pilot safety circuit.
• Inadequate pilot flame.
• Internal scaling in the heat exchanger.
• Inadequate gas pressure.

How To Fix:

Here are the appropriate fixes to each of these problems:

i) Pilot light doesn’t light

Check the gas supply. Make sure all manual gas shut-off valves are open. If they are, then you’ll need to bleed air from the gas line. To do this, hold down the gas control slide button and hit the pilot igniter button. 

Verify that a spark is being generated at the pilot area. You can do this by looking for a small, blue flame at the end of the pilot electrode. If you don’t see a flame, then the spark may not be working properly. Check the wire connection to the electrode to make sure it is secure. 

Clean the pilot orifice and pilot gas tubing. If the pilot assembly is blocked, you may need to clean the pilot orifice and pilot gas tubing. To do this, you can use a small wire brush or needle to remove any debris that may be blocking the flow of gas.

ii) Pilot light turns off during or after hot water use

If your Bosch tankless water heater pilot light turns off during or after hot water use, make sure that the water entering the heater is not preheated. 

Verify that the venting system meets the manufacturer’s specifications, and inspect all connections in the pilot safety circuit. If the pilot light still turns off, I recommend going through our detailed guide on bosch tankless water heater pilot light problem.

Bosch Electric Tankless Water Heater Troubleshooting

In this section, I will explain some common troubleshooting steps to help you diagnose and potentially resolve issues with your Bosch electric tankless water heater.

i) Cold Water Only – Neon Light Off

When a tankless water heater only provides cold water or has its neon light turned off, there can be various underlying reasons to consider. One possible cause is a low flow rate. If the water flow through the heater is below the activation point, the unit may not ignite and only deliver cold water.

Another potential reason is a plumbing crossover. A plumbing crossover occurs when there is an unintentional connection between the hot and cold water lines, resulting in cooler water at the tap. 

The flow transducer not spinning can also impact the water heater’s functionality. The flow transducer is responsible for detecting the water flow and triggering the ignition process. If it fails to spin properly, it may not activate the heater, leading to cold water output. 

A lack of electricity or supply failure is another possible cause. If there is no power reaching the water heater or if there is a supply failure, it will be unable to function and provide hot water. 

Tripped thermal cut-outs can also result in cold water output or a deactivated neon light. Thermal cut-outs are safety features that shut off the heater in the event of overheating. 

A voltage drop in the power supply can contribute to the water heater’s malfunction. Insufficient voltage can prevent the heater from operating properly, resulting in cold water.

Additionally, an inlet water temperature that is too cold can affect the heater’s performance. If the incoming water temperature is extremely low, it may require the heater to work harder to provide hot water. This can result in reduced output temperature or even cold water.

If one of the power supplies is not turned on, it can lead to cold water output or deactivated neon light. A tankless water heater typically requires multiple power supplies to function correctly. 

Premature element failure can also impact the water heater’s ability to provide hot water. If the heating elements within the unit fail prematurely, it can result in reduced or no hot water output.

Addressing these potential issues can help identify and resolve the reasons why a tankless water heater is only delivering cold water or has its neon light turned off. 

How To Fix:

First, check the flow rate. If it’s too low, you need to adjust it to get hot water. Next, inspect whether you’ve plumbing crossover. I’ve already talked about how you can do it earlier. Consult a plumber to rectify this issue.

Then, inspect the flow transducer by removing the front cover and looking at it. It can seem like the transducer is stationary even when it’s moving. So, turn off the hot water faucet and turn it back on to see if it’s really spinning. If it’s not spinning, you have to remove and flush the flow transducer.

Another possible cause is a lack of electricity or a supply failure. The circuit breaker or fuse box should be checked, and an electrician may be needed to resolve the issue.

Also, tripped thermal cut-outs can also cause the heater to malfunction. These should be checked for continuity using a multimeter. If one or more thermal cut-outs have tripped, it is necessary to identify the cause of overheating and reset the cut-outs to resume normal operation.

Moreover, a power supply voltage drop can affect the heater’s performance. An electrician should be contacted to ensure the voltage supplied is within the manufacturer’s specified range.

Additionally, the inlet water temperature being too cold can be an issue. Proper positioning of the heater based on the geographic location is important, and the temperature knob should be set to the maximum setting. Flow rates should also be checked to ensure they fall within the specified range.

Lastly, if the tankless water heater has multiple power supplies or circuits, all necessary power supplies should be turned on. If there are issues with the heater’s elements, such as premature failure, a licensed electrician should be contacted to verify the correct resistance.

ii) Water Not Hot Enough – Neon Light On

Here are some possible causes to address the problem of water not being hot enough when the neon light is on:

1. Incorrect plumbing connections
2. Tripped heating module thermal cut-outs
3. Feeding preheated water to the heater
4. Temperature dial set too low
5. High water flow rate
6. Plumbing crossover

How To Fix:

First, verify and correct plumbing connections by reconnecting the water supply to the inlet of the unit. This ensures proper water flow.

Next, check for any tripped heating module thermal cut-outs. Turn off the power to the heater, remove the cover, and test the continuity of each cut-out. If the continuity value is greater than 0.5 Ohms, it indicates tripping, and the cause should be determined and resolved.

If the water temperature is too low, increase the setting on the temperature dial located on the front of the water heater. 

To maintain proper water flow, adjust the water flow to stay within the specifications of the water heater. Refer to the manual for specific information on the recommended water flow rates.

To check for a plumbing crossover, turn off the power supply to the heater and close the cold water shut-off valve. Then, open all hot water taps supplied by the heater and wait for five minutes. If any water is running during this time, it indicates a plumbing crossover.

In such cases, it is recommended to consult Bosch customer support center or a professional plumber for assistance in resolving the crossover issue.

After completing the necessary tests, return the heater to service by reinstalling the cover. Open the inlet water supply and allow all hot water taps to run until no air is coming out of the fixtures.

Once the air is purged, shut off all hot water taps, turn on the power supply to the heater, and ensure it is functioning properly. This procedure prevents damage to the heating elements.

iii) The Temperature Of The Water Is Too Hot

If the water from your taps is scorching hot, you might be dealing with the issue of water temperature being too high. There can be several factors contributing to this problem and they are described below:

• Temperature dial set too high: The temperature knob on the water heater is set to a high level, resulting in excessively hot water.
• Restrictions in the plumbing: There are obstructions in the water path, which can restrict the flow of water through the heater and lead to overheating. This can be caused by debris or blockages in the heater’s inlet filter screen, faucet aerators, showerheads, or whole-house filters.
• Inlet water temperature is too warm: The water heater is being fed with water that is already preheated, which is not suitable for this specific water heater. It is designed for cold water feed only.

How To Fix:

To address the issue of the temperature being set too high on your water heater, follow the below guidelines:

Locate the temperature knob on the front of the water heater and turn it counterclockwise to lower the temperature to a cooler setting.  

Then check for any obstructions in the water path that may be preventing the flow of water through the heater if you are experiencing plumbing restrictions. This includes verifying that the inlet filter screen, faucet aerators, showerheads, and whole-house filters are clear of debris.

Also, disconnect the hot water pipe and verify the flow on the inlet side of the heater. Make sure there are no issues with the flow. If necessary, fully open the cold water isolation valve to ensure proper flow. 

You can refer to the maximum flow rates for your specific unit. For WH17, the maximum flow rate is 2.3 gallons per minute (gpm), and for WH27, it is 3.5 gpm. Ensure that the flow rate falls within these specifications.

Increase the flow rate wherever possible. Inadequate flow can contribute to higher water temperatures. Check for any restrictions in the plumbing system and remove any obstructions that may be impeding the water flow. 

Consider replacing low-flow showerheads and aerators with higher-flowing ones that have a higher gallons per minute (GPM) rating. This can help increase the flow of water and prevent excessive heating.

To resolve the problem of the inlet temperature being too hot, verify that the water heater is being fed with cold water only. This water heater is specifically designed for cold water input and is not suitable for preheated water or recirculation applications.

iv. Fluctuation Of Water Temperature

Here are some reasons why there is fluctuation in water temperature:

• Cold mix issue
• Fluctuating water pressure
• Changes in flow rate

How To Fix:

Clean or replace fixtures that might be causing restricted flow. This will help improve the mixing of hot and cold water and achieve a more balanced temperature. Also, adjust the temperature setting on the heater’s temperature adjustment knob. Gradually lower the temperature until the desired and comfortable hot water temperature is achieved.

Ensure that your home’s water pressure meets the recommended minimum requirement of 30 psi or greater (30-50 psi for well systems). This can be achieved by installing a pressure-reducing/regulating valve, such as Watts brand 25AUB-¾” or N35B-¾” or an equivalent model. This valve will help stabilize the water pressure supplied to the water heater, ensuring consistent temperature output.

To maintain a consistent water temperature and prevent fluctuations caused by changes in flow rate, follow these steps:

i) Adhere to heater specifications: Make sure to operate the water heater within its specified flow rate limits. Refer to the manufacturer’s guidelines or user manual to determine the maximum recommended flow rate for your specific model.

ii) Avoid sudden increases in flow rate: When using multiple fixtures simultaneously, ensure that the combined flow rate does not exceed the recommended limit. This will help maintain a stable water temperature.

When Automatic Adjustment Of Gas/Airflow Is Required?

Automatic adjustment of gas/airflow is required for the appliance in several situations, including:

• In Natural Gas installations where the energy content is less than 900 BTU/cu ft.
• If the operating conditions, such as gas pressure and composition, are different from the standard conditions specified in the manual. In such cases, the values from the manual take precedence over manifold gas pressure to ensure correct appliance tuning.
• After the installation, if the appliance repeatedly shows unresolved errors as described in Chapter 9 of the manual.
• When the appliance is converted to LPG and has an energy content of more than 2820 BTU/cu ft.
• After replacing the electronic control unit, fan, or gas valve.

How To Adjust Gas/Airflow Automatically?

To activate the automatic adjustment process on your water heater, you have to press and hold the buttons for 3 seconds. This will initiate the menu selection process.

Navigate and select the UC (Combustion Automatic Adjustment) menu using the buttons, Or press the button to enter the UC menu directly. This menu is specifically designed for automatic adjustment purposes.

Once you have entered the UC menu, the automatic adjustment process will begin. Pay attention to the display for further instructions. During this process, the Tap Symbol image will appear on the display. This indicates that the water heater is ready for adjustment.

To ensure adequate water flow, open a sufficient amount of hot water taps. For example, you can open one tub and two sinks simultaneously. Continue running the water until the tap symbol image disappears. This indicates that there is enough water flow for the adjustment process to take place.

By following these steps, you can activate the automatic adjustment process on your water heater and ensure optimal performance.

Why Does My Bosch Tankless Water Heater Keep Shutting Off?

If the volume of flowing cold water is not sufficient to exceed the minimum flow rate required to keep the water heater activated, it may result in the appliance shutting down during hot water usage. Tankless water heaters typically have a minimum flow rate requirement to ensure proper operation and prevent damage to the unit.

When the flow rate falls below the minimum threshold, the water heater may automatically shut down to prevent overheating and potential safety hazards. This can happen when there is a low demand for hot water or if there are restrictions in the plumbing system that limit the flow.

To avoid this issue, it is important to ensure that the minimum flow rate is consistently maintained during hot water usage.

How To Reset Bosch Tankless Water Heater? 

Resetting a Bosch water heater may be necessary if the unit is not heating water sufficiently and has been shut off as a safety measure. Resetting the unit is a straightforward process that requires basic knowledge of electrical appliances.

To reset the Bosch tankless water heater, press the red buttons located on the thermal cutouts of the heating elements. 

Visit our comprehensive guide on Bosch tankless water heater reset button if you need additional guidance. 

FAQs:

Wrapping Up

Every gas/electric appliance will malfunction over time, including the Bosch tankless water heater. The water heater may encounter issues such as failure to turn on the burner, delivery of excessively hot water, or no hot water at all. 

This Bosch tankless water heater troubleshooting guide provides solutions to all the common problems you could encounter. Make sure to check Bosch tankless water maintenance guide that is linked above so that your water heater lasts longer.

Well, before leaving you can also check out our comprehensive guide on Stiebel Eltron tankless water heater troubleshooting if you have a Stiebel Eltron tankless water heater. You’re welcome there!