Egg Timer on Vaillant Boiler: What It Means & How to Fix It

Last Updated on February 18, 2025

If you own a Vaillant boiler and have noticed an egg timer symbol on the display, you might be wondering what it means and whether your boiler needs fixing. This article will explain the egg timer on a Vaillant boiler, why it appears, and how to resolve it.

What Does the Egg Timer Symbol on a Vaillant Boiler Mean?

The egg timer icon on a Vaillant boiler, also known as the hourglass symbol, is not an error code but a status indicator. It signifies that the boiler is in a transitional phase, preparing to heat water or adjusting its operation for efficiency.

Common Reasons for the Egg Timer Icon Appearing

Here’s a deeper look into the most common reasons why the egg timer might appear:

1. Preheat Function

Many Vaillant boilers, especially combi boilers, come with a preheat function designed to keep a small amount of hot water readily available. This feature reduces waiting time when you turn on a tap, ensuring you get hot water almost instantly.

• When the preheat function is active, the boiler intermittently fires up to maintain a preheated water supply, causing the egg timer to appear.
• If your boiler has Vaillant’s AquaComfort system, this function is standard, and the egg timer symbol will flash when the system is maintaining the preheated water.
• If you don’t need instant hot water, you can disable the preheat function in the settings to conserve energy.

2. Delayed Ignition

When your heating or hot water system requests heat, the boiler doesn’t ignite instantly. Instead, it goes through a startup sequence, which includes safety checks and ignition preparation.

• During this time, the boiler runs a diagnostic check, ensuring factors like gas supply, airflow, and system pressure are optimal before ignition occurs.
• The egg timer appears while this process takes place, typically lasting a few seconds to a minute.
• If the icon persists and your boiler isn’t heating, it may indicate a more serious issue such as a faulty ignition electrode or low gas pressure.

3. Modulation in Progress

Vaillant boilers use modulating burners, which means they adjust their flame output based on heating demand rather than switching on and off frequently. This helps maintain consistent temperatures and improves energy efficiency.

• When the boiler is modulating, it may reduce or increase its output, causing the egg timer symbol to appear briefly.
• This process prevents unnecessary energy consumption, making the boiler more efficient compared to older models that operate at a fixed high output.
• The egg timer should disappear once the boiler reaches a stable output level.

4. Boiler Running a Cycle

During normal operation, the boiler doesn’t constantly fire at full power. Instead, it runs in cycles, turning on and off as needed to maintain temperature levels.

• When the boiler is between heating cycles, the egg timer may appear to indicate that the system is in standby mode before restarting.
• If you notice the egg timer appearing frequently or for long periods, it could indicate that the boiler is short cycling, which may be due to incorrect system settings, a clogged heat exchanger, or a faulty thermostat.

How to Fix the Egg Timer Symbol on a Vaillant Boiler

Most of the time, the egg timer symbol is a normal part of your boiler’s operation. However, if it remains visible for a long time or the boiler isn’t providing hot water or heating, here are some troubleshooting steps to fix it:

1. Wait and Monitor

Before assuming there’s an issue, observe the boiler for a few minutes:

• If the egg timer disappears within a short time, the boiler was likely in a normal operating mode such as preheating or modulating.
• If the symbol remains for more than 10–15 minutes, or you experience delayed heating/hot water, further action may be needed.

2. Check the Boiler Settings

Vaillant boilers allow users to toggle the preheat function via the settings. If you want to adjust the preheat setting:

• For eco mode: Turn off the preheat function to reduce gas usage.
• For instant hot water: Keep preheat on, but expect the egg timer symbol to appear intermittently.
• If your home’s heating schedule isn’t working as expected, check the thermostat and timer settings to ensure they are correctly programmed.

3. Reset the Boiler

If your boiler isn’t responding or continues to show the egg timer without producing heat, a simple reset may resolve the issue:

• Locate the reset button (usually marked with an ‘R’ or circular arrow symbol).
• Press and hold the button for 5–10 seconds, then wait for the boiler to restart.
• If the boiler resumes normal function, the issue was likely a minor glitch.

4. Check for Error Codes

If the egg timer icon remains alongside an error code, it may indicate a more significant fault:

• Look up the error code in your Vaillant boiler manual to determine the issue.
• Common error codes that may appear alongside the egg timer include:
  • F.22 (Low water pressure)
  • F.28 (Ignition fault)
  • F.75 (Pump issue or pressure sensor fault)
• If a fault code is present, you may need a Gas Safe engineer to investigate further.

5. Inspect the Water Pressure

Low water pressure can prevent the boiler from firing up, leading to the egg timer symbol staying on for an extended time.

• Check the pressure gauge on your boiler. It should be between 1.0 and 1.5 bar.
• If the pressure is too low (below 1 bar), you’ll need to repressurise the boiler by opening the filling loop until the correct pressure is reached.
• If the pressure drops frequently, there may be a leak in the system that requires professional attention.

6. Call a Gas Safe Engineer

If none of the above steps resolve the issue, or if the egg timer remains on indefinitely, you should contact a Gas Safe registered engineer to inspect your boiler.

• Signs you need professional help:
  • The boiler is not producing heat or hot water.
  • The pressure keeps dropping despite being topped up.
  • The egg timer appears alongside a persistent error code.
  • The boiler is making unusual noises (gurgling, banging, whistling).

When to Consider a New Boiler

If your Vaillant boiler is frequently showing faults, losing efficiency, or more than 10–15 years old, it may be time to consider a boiler replacement. New A-rated boilers offer improved energy efficiency, lower heating bills, and enhanced reliability.

Request a Free Boiler Quote Today!

Upgrading to a new boiler could save you money and improve your home’s heating efficiency. Simply answer a few quick questions, and we’ll provide a free, no-obligation quote tailored to your budget and needs.

Not sure which Vaillant boiler is right for you? Check out our Vaillant boiler reviews and prices page to compare models, features, and costs before making a decision.