Main Eco Compact Error Code E118 - Boiler Group (2024)

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• What is Primary System Water Pressure and what does it do?
• E118 Red Flags
• E118 Troubleshooting Tips
• What can you do as a Homeowner
• What to do as a Gas Engineer
• Video Content
• FAQ’S

In the context of a boiler, primary system water refers to the water that circulates within the primary heating system. The primary system is responsible for transferring heat from the boiler to various components within a heating system, such as radiators, baseboard heaters, or underfloor heating pipes.

The primary system water absorbs heat from the boiler through a heat exchanger or directly from the boiler’s primary circuit. It then carries the heat to the different parts of the heating system, providing warmth to the surrounding areas. Once it releases the heat, the cooled primary system water returns to the boiler to be reheated and continue the cycle.

It’s worth noting that the primary system water is distinct from the water used for other purposes in a boiler system, such as domestic hot water supply. Boilers can have separate circuits or systems for different water needs, but the primary system water specifically refers to the water used for space heating.

The E118 Error code will only appear if the boiler’s pressure goes under 0.5 Bar.

A red flag of low primary system water pressure in a boiler indicates a potential issue with the water pressure level within the primary heating system. When the pressure drops below the recommended or normal range, it can signify a problem that needs attention. Here are a few possible causes and implications of low primary system water pressure:

• Water leakage: Low pressure could be a result of water leakage within the system. Leaks may occur in various components such as pipes, valves, or fittings, causing a loss of water and subsequent pressure drop.
• Faulty pressure relief valve: The pressure relief valve is designed to release excess pressure from the system. If the valve is malfunctioning, it may be constantly open or not functioning at all, leading to a drop in pressure.
• Air in the system: Air pockets or trapped air within the primary system can cause a decrease in pressure. Air can enter the system during maintenance, repairs, or if the system hasn’t been properly bled off air during initial installation.
• Expansion vessel issues: The expansion vessel helps accommodate the expansion and contraction of water as it heats up and cools down. If the expansion vessel is faulty or has lost its air charge, it may not effectively maintain the required pressure.
• Filling loop not closed properly: The filling loop is used to add water to the system when necessary. If the filling loop valve is not closed tightly after filling, it can result in a gradual loss of pressure.
• Low primary system water pressure can lead to reduced efficiency and performance of the heating system. It may result in insufficient heat distribution, potential damage to the boiler components, or even boiler shutdown if the safety mechanisms are triggered. It is essential to investigate and address the cause of low water pressure to ensure the boiler operates safely and efficiently. Consulting a professional heating engineer or plumber is recommended to diagnose and resolve the issue.

Homeowners – What you can do as a homeowner?

Qualified Gas Engineers – Troubleshooting Tips, And What to Do as a Qualified Gas Engineer?

1. Check the pressure gauge: Verify that the pressure gauge is functioning properly and accurately. Make sure it is not faulty or stuck, as this can lead to incorrect pressure readings.
2. Inspect for leaks: Carefully examine the system for any visible signs of water leakage. Check pipes, valves, fittings, and radiator connections for drips, puddles, or dampness. If you find any leaks, they should be promptly repaired or replaced by a qualified professional.
3. Bleed air from the system: If air has entered the system, it can cause pressure issues. Locate the bleed valves on radiators or at high points in the system and release any trapped air. Follow the manufacturer’s instructions or consult a professional if you’re unsure how to bleed the system.
4. Check the pressure relief valve: Inspect the pressure relief valve to ensure it is functioning correctly. It should open and close properly, releasing excess pressure when necessary. If the valve is faulty, it may need to be repaired or replaced by a professional.
5. Verify the expansion vessel: The expansion vessel helps maintain system pressure by accommodating the expansion and contraction of water. Check the vessel’s air charge and make sure it is within the recommended range. If the vessel’s air charge is incorrect, it may need to be adjusted or replaced.
6. Ensure the filling loop is closed: If you have recently topped up the system using the filling loop, make sure the filling loop valves are closed properly. Even a small leak from the filling loop can cause a gradual loss of pressure over time.
7. Consult a professional: If you have gone through these troubleshooting steps and the low primary system water pressure issue persists, it is advisable to seek assistance from a qualified heating engineer or plumber. They have the expertise and knowledge to diagnose and resolve more complex problems with the boiler system.

• Check the water pressure: Make sure the pressure gauge is between 1 bar and 1.5 bar (This is normally a green triangle) (Picture of Pressure Gauge)

• Check the stop tap is turned on (Lefty loosey Righty tighty)
• Ensure the filling loop is closed: the levers will cross the pipe if closed (Picture of closed combi filling loop)

• Repressurising the boiler: If the boiler is really low on pressure repressurise it up to 1 bar > 1.5 Bar (Check out our video on how to repressurise a Baxi main eco compact boiler)
• Consult a professional: If you have gone through these steps and the low primary system water pressure issue persists, it is advisable to seek assistance from a qualified heating engineer or plumber. They have the expertise and knowledge to diagnose and resolve more complex problems with the boiler system.

• Check the pressure gauge: Verify that the pressure gauge is functioning properly and accurately. Make sure it is not faulty or stuck, as this can lead to incorrect pressure readings.
• Bleed air from the system: If air has entered the system, it can cause pressure issues. Locate the bleed valves on radiators or at high points in the system and release any trapped air. Follow the manufacturer’s instructions or consult a professional if you’re unsure how to bleed the system.

• Inspect for leaks: Carefully examine the system for any visible signs of water leakage. Check pipes, parts, valves, fittings, and radiator connections for drips, puddles, or dampness. If you find any leaks, they should be promptly repaired or replaced by a qualified professional.
• Check the pressure relief valve: Inspect the pressure relief valve to ensure it is functioning correctly. It should open and close properly, releasing excess pressure when necessary. If the valve is faulty, it may need to be repaired or replaced by a professional. A big hint of this is that the blow off, (Prv outlet Pipe) Will be dripping on the outside.
• Verify the expansion vessel: The expansion vessel helps maintain system pressure by accommodating the expansion and contraction of water. Check the vessel’s air charge and make sure it is within the recommended range. If the vessel’s air charge is incorrect, it may need to be adjusted or replaced. There should be a tag on the side of the expansion with all the information needed.
• Ensure the filling loop is closed: If you have recently topped up the system using the filling loop, make sure the filling loop valves are closed properly. Even a small leak from the filling loop can cause a gradual loss of pressure over time.

If the Expansion vessel is broken and will not pump up or is really badly damaged, then we recommend replacement of the expansion vessel and at the same time the PRV, As they do stick but it is completely up to what the qualified engineer thinks is best for the job.

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