Vaillant ecoTEC plus 618

Questions and Answers

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Christopher JohnsonAug 25, 2025
Why won't my Vaillant Boiler start?
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  spowellAug 25, 2025
  If your Vaillant Boiler fails to ignite, it could be due to faults in the gas supply, such as a defective gas meter, air in the gas line, low gas flow pressure, or a tripped fire protection tap. It can also be caused by issues with the gas fitting, incorrect gas setting, a defective igniter, interrupted ionization current, faulty earthing, or defective electronics. Diagnose and rectify issues in the gas supply and fittings.
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David JohnsonSep 1, 2025
Why is there no pressure change when the pump turns on in my Vaillant ecoTEC plus 618?
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  Matthew MorenoSep 1, 2025
  If no sudden change in pressure is detected when turning on the pump in your Vaillant Boiler, it could be due to a defective water pressure sensor or pump, or too little water in the appliance. Ensure sufficient water supply and inspect the pump.
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Chloe HicksSep 1, 2025
What to do if the drinking water outlet probe stopped in my Vaillant ecoTEC plus 618 Boiler?
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  nicholsonjosephSep 1, 2025
  If the drinking water outlet probe has stopped (
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Danielle WilliamsSep 2, 2025
Why does my Vaillant ecoTEC plus 618 Boiler show a flame when the gas valve is off?
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  qleachSep 2, 2025
  If your Vaillant Boiler shows a secondary light, where the ionization signal reports a flame even when the gas valve is turned off, it could be due to defective gas solenoid valves or a defective flame detector. Inspect and replace the gas valves or flame detector.
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Kathleen BlairSep 2, 2025
What causes a short circuit in the tank sensor of my Vaillant ecoTEC plus 618?
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  Maureen RodriguezSep 2, 2025
  A short circuit in the tank sensor of your Vaillant Boiler can be caused by a defective NTC, an earth leak/short circuit in the cable loom, or a damp plug connection. Inspect and replace the NTC or repair damp connections.
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Charles ClineSep 3, 2025
What does it mean 'No valid DSN in AI and/or BMU' in Vaillant Boiler?
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  Lauren OrtizSep 3, 2025
  If your Vaillant Boiler displays 'No valid DSN in AI and/or BMU', it indicates a spare part failure where the AI and motherboard were interchanged at the same time. Replace faulty components to resolve DSN issue.
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Timothy GilbertSep 3, 2025
What to do if my Vaillant ecoTEC plus 618 appliance does not start and ignition fails?
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  Joseph MeyersSep 3, 2025
  If your Vaillant Boiler fails to start and ignition attempts fail, there may be faults in the gas supply, such as a defective gas meter or gas pressure detector, air in the gas, gas flow pressure too low, or a disengaged fire protection tap. There may be faults in the gas valve, wrong gas setting, defective igniter (ignition transformer, ignition cable, ignition plug), stopped ionization current (cable, electrode), faulty earthing in the appliance or defective electronics. Inspect the gas supply and ignition components for faults.
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Christopher GomezSep 4, 2025
What to do if the flame goes off during operation of my Vaillant ecoTEC plus 618 Boiler?
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  edavisSep 4, 2025
  If the flame goes off during operation and subsequent ignition attempts fail, it could be due to a temporarily stopped gas supply or faulty earthing of the appliance. Check the gas supply and earthing connections.
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brian03Sep 4, 2025
Why is there a dry fire in my Vaillant Boiler?
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  Sarah JonesSep 5, 2025
  A dry fire in your Vaillant Boiler can occur due to too little water in the appliance, a defective water pressure sensor, a defective cable to the pump or water sensor, a blocked or defective pump, or a pump output that is too low. Ensure sufficient water supply and check the pump and sensors for faults.
A
Anthony MaldonadoSep 5, 2025
What to do if my Vaillant Boiler shows water shortage and large temperature difference?
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  Jodi ChanSep 5, 2025
  If your Vaillant Boiler indicates a water shortage and a large temperature difference between the flow and return NTC, the pump might be blocked or defective, the pump output might be too low, or the flow and return NTCs might be interchanged. Check and unblock or replace the pump and verify the NTC placement.

Summary

1 Introduction

1.1 Notes on the documentation

Guidance on documentation usage, symbols, CE marking, and data badge.

1.2 Introduction

Overview of the ecoTEC boiler and installation requirements.

1.3 General Notes

General notes on boiler design, mounting, and flue systems.

1.4 CE marking

Details of compliance with EU directives and basic requirements.

2 Boiler specifications

2.1 Technical data

Detailed technical specifications and performance data for ecoTEC boilers.

2.2 Dimensions

Diagrams and measurements for boiler installation and clearances.

2.4 Installation

Diagrams showing function elements of combination and system boilers.

3 General requirements

3.1 Preliminary remarks for room sealed appliances

Requirements for room-sealed appliances and flue system installation.

3.2 Related documents

List of related documents and British Standards for installation.

3.4 Installation site

Guidelines for selecting an appropriate and safe installation location for the boiler.

3.5 Gas supply

Requirements and checks for the gas supply to the boiler.

3.6 Flue pipe

Information on standard and optional flue pipe systems and their installation.

3.7 Flue termination

Details and diagrams for correct flue termination positions.

3.9 Electrical supply

Requirements for the mains electricity supply connection, including safety.

3.10 Guide to system requirements

Guidance on water circulation, filling, pressure, and expansion vessel requirements.

4 Boiler installation sequence

4.1 Transporting the appliance

Recommendations and safety guidelines for lifting and transporting the boiler.

4.2 Required minimum distances;assembly clearances

Diagrams showing minimum clearances required around the boiler for installation.

4.3 Flue exit

Instructions for marking and preparing the flue exit hole.

4.4 Fitting the boiler hanging bracket

Steps for securely fitting the boiler's hanging bracket to the wall.

4.9 Gas connection

Instructions for safely connecting the gas supply to the boiler.

4.11 Condensate drain pipe

Guidance on connecting the condensate drain pipe and its installation requirements.

4.12 Heating connection

Instructions for connecting the heating circuit pipework to the boiler.

4.14 Electrical connection

General requirements and safety precautions for electrical connections.

4.15 Controls

Information on Vaillant controls and accessories for the ecoTEC series.

5 Commissioning Part I

5.1 Preliminary electrical checks

Checks to be performed on the electrical installation before commissioning.

5.2 Gas supply

Inspection, leak checks, and purging of the gas installation.

5.4 Filling and bleeding the heating system

Steps for filling and bleeding the heating system, including using test programs.

5.6 Filling the condensate siphon

Instructions for filling the condensate siphon to prevent fume escape.

5.8 Adjusting the by-pass

Procedure for adjusting the appliance's adjustable by-pass valve.

5.9 Checking the gas supply

Steps for checking gas inlet working pressure and gas rate.

5.10 Refitting the case

Instructions for refitting the boiler's front casing after maintenance.

6 Functional checks (commissioning part II)

6.1 Functional checks

Procedure for performing functional checks before commissioning.

6.1.2 Heating

Procedure for checking heating operation and status displays.

6.2 Handing over to the user

Instructions for handing over the appliance to the user, including settings and explanations.

7 Inspection and maintenance

7.1 Initial inspection

Recommendations for initial inspection and frequency of servicing.

7.1.1 Safety instructions

Crucial safety instructions to be followed before starting any maintenance work.

7.2 Servicing the burner module

Detailed steps for removing and servicing the burner module.

7.3 Cleaning the condensate siphon

Procedure for cleaning the condensate siphon, including safety notes.

8 Troubleshooting

8.1 Logical fault finding procedure

Step-by-step checks for identifying and resolving boiler faults.

8.1.1 Status codes

Explanation of status codes displayed by the appliance.

8.1.2 Diagnostic codes

Accessing and understanding diagnostic codes for troubleshooting.

8.1.4 Fault memory

How to access and review the stored fault memory.

9 Parts replacement

9.1 Safety instructions

Essential safety precautions before replacing boiler components.

9.2 Replacing burner

Procedure for replacing the burner module, including safety.

9.3 Replacing fan or gas valve

Steps for replacing the fan or gas valve, with safety precautions.

9.5 Replacing primary heat exchanger

Instructions for replacing the primary heat exchanger, with safety.

9.6 Replacing electronics and display

Procedure for replacing the electronic components or display unit.

9.7 Check CO2 content and if necessary set (air ratio adjustment)

How to check and adjust CO2 content for optimal combustion.

10 Recycling and disposal

11 Vaillant service

Appendix

Vaillant ecoTEC plus 618 Specifications

General

Model	ecoTEC plus 618
Category	Boiler
Output	18 kW
Dimensions	720 x 440 x 338 mm
Fuel Type	Natural Gas
ERP Rating	A
Mounting	Wall-mounted
Warranty	5 years
Boiler Type	Combi
Efficiency	94%