What Causes Water Heater High Temperature Shutdown & How To Fix

This is a complete guide on Water Heater High Temperature Shutdown. In this article, what I am going to break down: 

• What does high temperature shutdown mean on a water heater?
• Reset the gas control valve to fix the high-temp shutdown: The initial step
• What causes a high-temperature shutdown on a water heater and how do you fix them?
• Tips to prevent high-temperature shutdown on a gas water heater

What Does High Temperature Shutdown Mean On A Water Heater?

High-temperature shutdown on a water heater means the temperature inside the tank exceeds 180°F, causing the unit to shut off. Typically, the water heater’s high-temperature shutdown is a safety feature. It shuts the gas supply off to the burner when the temperature exceeds a certain preset limit (around 180°F). As a result, it protects the unit from overheating and the users from the risk of scalding. 

When the high-temperature shutdown occurs, the status light on the gas control valve will blink four times. It alerts you about the high-temperature condition and tells you to take action immediately to resolve it. 

Reset the Gas Control Valve To Fix High Temp Shutdown: The Initial Step

If you observe the status light blinking four times, reset the gas control valve first to fix the high-temperature shutdown. 

Note: The resetting procedure will only work  if you have a gas water heater with a Honeywell gas control valve. 

Follow the below procedure step-by-step to reset the gas control valve: 

• Press the gas control/thermostat knob and set it to Pilot.

• Press and hold down the thermostat knob.

• While holding down the thermostat knob, start striking the piezo igniter button until the status light comes on and blinks four times. 

• Once the light comes on and blinks four times, set the thermostat knob to Very Hot. Count 10 seconds (1, 2, 3, 4, 5, 6, 7, 8, 9, 10). 

• Then, set the thermostat knob to Hot and count for 10 seconds again. 

• Next, move the thermostat knob to Pilot and count for ten seconds. 

• Finally, set the thermostat knob to the desired temperature setting. And you will hear the burner come on. 

What actually happens is- the series of steps you go through will help you overcome the lockout of the Honeywell gas control valve. In short, you don’t need to replace the gas control valve to fix the high-temp shutdown problem. 

However, if the Honeywell gas control valve reset doesn’t bring any luck, you may have to replace the gas control valve. I will describe the replacing procedure in the chapter What Causes Water Heater High-Temperature Shutdown below. 

What Causes Water Heater High Temperature Shutdown?

A faulty thermostat, defective gas control valve, and scale buildup in the tank can cause a high-temperature shutdown on a water heater. 

Defective Thermostat

A defective thermostat will fail to regulate the temperature and cause a high-temperature shutdown. The thermostat is responsible for regulating the temperature in the tank. If it malfunctions, the thermostat fails to monitor temperature, leading to overheating and triggering the high-temp shutdown. 

Here are the signs you will observe if the thermostat is at fault: 

• Insufficient or too hot water
• The burner won’t come on
• Overheating

How To Fix: 

Before replacement, test the thermostat. To test the thermostat: 

• Turn on the water heater.
• Turn the thermostat knob to the desired temperature setting like 120-degree F.
• Get a thermometer and measure the temperature of the outlet water. If it’s not accurate or far from the set temperature, understand the thermostat is at fault. 

You should replace the thermostat if it’s at fault. Unfortunately, the thermostat knob is a part of the gas control valve. It means you need to replace the entire gas control valve. 

Defective Gas Control Valve

Due to a faulty gas control valve, gas flow to the burner will be irregular. As a result, the unit will heat excessively, triggering the high-temp shutdown. 

How To Fix: 

Before replacing the gas control valve, reset the gas control valve following the instructions I mentioned above. Most of the time, resetting the gas control valve will fix the high-temp shutdown error. 

If resetting the unit doesn’t work, you must replace the gas control valve. I recommend you check out the following tutorial to learn how to replace the gas control valve like a pro: 

Read Also: Rheem Water Heater Gas Valve Problem

Sediment Buildup

Over time, sediment can build up at the bottom of the tank. This buildup can insulate the water from the heating source. Consequently, it causes the burner to run longer to gain the desired temperature setting, leading to overheating. 

How To Fix: 

Flush the tank to remove sediment buildup from the bottom of the tank. To drain the water heater, follow these steps: 

• Close the water supply to the unit.
• Shut off the gas supply to your water heater.
• Locate the drain valve at the bottom of the unit and attach a garden hose to the drain valve. Then, place the other end to the nearest floor drain or outside.
• Open the drain valve by using a screwdriver.
• Once you drain the tank completely, close the drain valve. 
• Refill the tank.
• Restore power to the unit.

If the hardness of water is high, you can install a water softener. It will help remove minerals from the supply of water. 

Read Also: How To Drain Richmond Water Heater?

Dirty Burner

A dirty or clogged burner is responsible for improper combustion. Improper combustion can cause the burner to produce excessive heat, leading to high temperatures and triggering the shutdown. 

How To Fix: 

Clean the burner like a pro by following the below step-by-step procedure: 

• Turn off the gas supply to the unit by turning the gas valve right.

• Remove the access panel from the bottom of the unit that conceals the burner assembly. 

• Disconnect the thermopile, temperature sensor, and igniter from the gas control valve. 

• Use a 7/16″ wrench to disconnect the gas supply line that feeds into the gas control valve. Then, disconnect the main gas supply line from the gas control valve/thermostat using a 3/4″ wrench. 

• Remove the two screws on the filter door using a T20 Torx. Then, use an 11/32 nut driver to remove the top screws on the filter door. Next, use the T20 Torx to remove the screws that hold the burner in place. 

• Slide out the burner assembly carefully. Then, clean the burner using a wet/dry vacuum with a brush attachment. Don’t forget to clean the pilot tube and orifice. 

• Once you clean the burner, reassemble everything. Then, turn on the gas supply and light the pilot to verify proper operation. 

Malfunctioning Pressure Relief Valve

A pressure relief valve is also a safety feature. It releases excessive pressure that builds up in the tank, which can cause a water heater explosion. If the pressure relief valve fails to work as intended, the pressure keeps building in the tank and causes overheating. 

How To Operate Pressure Relief Valve Manually: 

First, operate the pressure relief valve manually. Follow the instructions below to operate the pressure relief valve on the water heater: 

• Locate the pressure relief valve at the top or side of the water heater.
• Lift the lever or handle on the top of the pressure relief valve.
• Once you lift the lever, you will hear a rush of air or see water coming from the valve. 

If you fail to lift the handle or there is no water from the valve, I bet the pressure relief valve is at fault. It means you need to replace the pressure relief valve. Never try to replace this part by yourself. Call a professional to make the replacement. 

Venting Issues

Proper vent installation is a must for proper combustion. If you install the vent improperly or there is a blockage in the vent, gasses like carbon dioxide won’t go out of the home. Consequently, temperature will build up in the tank and exceed the safety level, causing the high-temp shutdown to trigger. 

How To Fix: 

Check the vent exhaust outside of the home for blockage. Verify there is nothing like a bird’s nest in the vent pipe that could clog the vent. Release the restrictions from the vent. Next, ensure that the plumber installed the vent according to the instructions mentioned in the user manual. 

Defective Safety Features

Some gas water heaters come with a high-temperature limit switch. If it’s at fault, the limit switch doesn’t work or gets activated when needed. Because of the bad safety switch, the unit will heat improperly or excessively. 

Tips To Prevent High Temperature Shutdown On A Water Heater?

You can avoid the high-temperature shutdown condition by following the below tips: 

• Set Temperature Properly: Set the gas control/thermostat knob between 120 to 140 sets, which is considered a safe and comfortable temperature setting. 

• Flush The Tank: Drain the tank regularly to prevent sediment buildup at the bottom of the tank. Based on the hardness of the water, you should flush the tank once a year or every six months. 

• Install A Water Softener: You can install a water softener to remove minerals from the supply water. It will prevent the buildup of sediment at the bottom of the tank. 

• Inspect the Pressure Relief Valve: Check the pressure relief valve periodically or every month to ensure proper operation. It helps release excess pressure from the tank and prevent overheating. 

• Inspect the Ventilation: Check the vent at the exhaust and ensure there is no blockage or restriction. Restriction-free or proper ventilation is essential for healthy combustion and the prevention of overheating. 

• Inspect the Burner: Check the burner chamber periodically for debris buildup. If the burner is dirty, remove the burner assembly and vacuum the burner. 

• Monitor Gas Pressure: Monitor the gas pressure and ensure it’s within the specifications mentioned in the user manual. Improper gas pressure can lead to improper combustion and overheating. 

FAQs

What happens if your water heater temperature is too high?

Too high water temperature will increase pressure in the tank, which can cause overheating or even explode the tank. Fortunately, every gas tank water heater has a safety feature called water heater high temp shutdown. When the temperature exceeds the safe level, it will trigger the safety feature and turn off the unit immediately.

What do you do when your hot water heater is overheating?

Find the underlying reasons that cause overheating. Several factors like faulty thermostats, mineral deposits, and clogged pressure relief valves are responsible for overheating. Resolve those issues to avoid overheating. 

How do you reset a high limit switch on a water heater?

Locate the high-limit switch near the burner assembly at the bottom of the unit. Remove the access panel and press the high-limit switch to reset it on a water heater. 

End-Note

Water heater high-temperature shutdown is a safety feature on a gas water heater. When the temperature inside the tank exceeds 180 degrees Fahrenheit, the unit triggers the high-temp shutdown. 

The high-temperature shutdown will occur due to a faulty thermostat, sediment buildup, clogged pressure relief valve, and dirty burner. When this condition occurs, reset the gas control valve to fix the high-temp shutdown. If resetting the valve doesn’t bring any luck, try other troubleshooting steps mentioned in this article. 

Maintain the water heater regularly to avoid a high-temperature shutdown. Good Luck!