Vaillant ecoTEC plus 637 User Manual (English)

Questions and Answers:

S
Shelby ChavezAug 25, 2025
What to do if my Vaillant ecoTEC plus 637 appliance does not start and ignition fails?
- A
  Aaron BellAug 25, 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.
P
Paula HigginsAug 25, 2025
What to do if the flame goes off during operation of my Vaillant ecoTEC plus 637 Boiler?
- A
  Arthur MitchellAug 26, 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.
C
Carol MccoyAug 26, 2025
Why is there a dry fire in my Vaillant ecoTEC plus 637?
- J
  johnstondebraAug 27, 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.
B
Barbara RodriguezAug 27, 2025
What to do if my Vaillant ecoTEC plus 637 shows water shortage and large temperature difference?
- M
  Ms. Sarah MatthewsAug 27, 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.
E
Eugene BensonSep 8, 2025
What to do if my Vaillant ecoTEC plus 637 electronics temperature is too high?
- L
  Lynn RobertsSep 8, 2025
  If the electronics temperature is too high, it may be due to an external effect causing the electronics to overheat, or the electronics may be defective. Ensure proper cooling and replace the defective electronics.
T
Tina HamptonSep 7, 2025
What does EEPROM error mean in my Vaillant ecoTEC plus 637 Boiler?
- K
  Keith DavisSep 7, 2025
  An EEPROM error indicates that the electronics are defective. Replace the defective electronics.
H
hannahmontgomerySep 8, 2025
What does it mean if my Vaillant ecoTEC plus 637 Boiler displays electronics/NTC fault?
- J
  Joel ToddSep 8, 2025
  An electronics/NTC fault indicates a short-circuit in the flow or return NTC, or that the electronics are defective. Check and replace the NTC or repair the electronics.
J
Jeremy WellsSep 2, 2025
What does it mean if my Vaillant Boiler indicates a gas valve control defect?
- J
  jenniferaustinSep 2, 2025
  A gas valve control defect could mean there is a short circuit or earth (ground) leak in the cable harness to the gas valves, the gas valve assembly is defective (earth/ground leak from coils), or the electronic control system is defective. Inspect and repair the gas valve control circuit.
A
Alexis SotoAug 31, 2025
Why is the safety temperature limiter by NTC activated in my Vaillant Boiler?
- J
  James CarterAug 31, 2025
  The safety temperature limiter by NTC might be activated because the Flow-NTC is not correctly thermal-connected or is defective, causing the appliance not to shut down. Check the thermal connection of the Flow-NTC and replace it if defective.
R
Rachael WelchSep 1, 2025
Why is there incorrect sensing of flame in my Vaillant Boiler?
- N
  Nichole NicholsonSep 1, 2025
  Incorrect sensing of flame in your Vaillant Boiler is caused by a defective flame detector. Replace the flame detector.

Vaillant ecoTEC plus 637 Specifications

General

Model	ecoTEC plus 637
Category	Boiler
Output	37 kW
Dimensions	720 x 440 x 338 mm
Fuel Type	Natural Gas
Flow Rate	15.2 L/min
Mounting	Wall-mounted
Max working pressure	3 bar
Efficiency	94%

Summary

1 Introduction

1.1 Notes on the documentation

Guidance on using the documentation and understanding symbols.

1.2 Introduction

General overview of the ecoTEC boiler and its purpose.

1.3 General Notes

Basic notes on the boiler design and installation suitability.

1.4 CE marking

Compliance with EU directives for gas appliances and EMC.

1.5 Gas council numbers

List of gas council approval numbers for ecoTEC appliances.

2 Boiler specifications

2.1 Technical data

Detailed technical specifications including output, dimensions, and performance data.

2.2 Dimensions

Diagram and measurements for the boiler's physical dimensions.

2.4 Installation

Information regarding the installation of the boiler and its components.

2.5 Type plate

Location and information found on the boiler's type plate.

3 General requirements

3.1 Preliminary remarks for room sealed appliances

Initial considerations for installing room-sealed appliances.

3.2 Related documents

List of relevant standards and documents for boiler installation.

3.3 Contents included with delivery

Details of items supplied with the Vaillant ecoTEC boiler.

3.4 Installation site

Guidance on selecting an appropriate location for boiler installation, considering clearances and environment.

3.5 Gas supply

Requirements for gas supply, pipework, and connection to the boiler.

3.6 Flue pipe

Details on approved Vaillant flue pipes and systems for safe exhaust removal.

3.7 Flue termination

Specifications for flue terminal positioning to ensure safety and proper operation.

3.8 Air supply

Recommendations for air supply requirements for the boiler's operation.

3.9 Electrical supply

Requirements for the electrical connection, including voltage, fuse rating, and safety.

3.10 Guide to system requirements

Recommendations for the central heating water circulation system, pipework, and cleaning.

3.11 Pump specifications

Details on the boiler's internal circulating pump specifications.

3.12 Condensate trap

Information about the boiler's condensate trap and its function.

4 Boiler installation sequence

4.1 Transporting the appliance

Guidelines and safety measures for safely transporting the boiler unit.

4.2 Required minimum distances/assembly clearances

Specifies the necessary space around the boiler for installation and servicing.

4.3 Flue exit

Instructions for positioning and preparing the flue exit point.

4.4 Fitting the boiler hanging bracket

Steps for securely mounting the boiler's hanging bracket.

4.5 Installing the flue system

Guidance on installing the air/flue duct system according to specific instructions.

4.6 Fitting the boiler

Procedures for lifting and mounting the boiler onto its bracket.

4.7 Removing the front case

Steps for safely removing the boiler's front casing.

4.8 General instructions for heating system

General precautions related to the heating system before boiler connection.

4.9 Gas connection

Instructions for safely connecting the gas supply pipe to the boiler.

4.10 Cold water mains inlet and hot water outlet

Procedures for connecting the cold water inlet and hot water outlet pipes.

4.11 Condensate drain pipe

Guidance on connecting and routing the condensate drain pipe to prevent freezing and blockages.

4.12 Heating connection

Steps for connecting the central heating flow and return pipes to the boiler.

4.12.1 Heating flow and return connection

Detailed instructions for connecting the heating flow and return pipes.

4.12.2 Pressure Relief Valve

Procedure for installing the pressure relief valve's drain pipe.

4.13 Connecting the flue system to the boiler

Reference to separate instructions for connecting the flue system.

4.14 Electrical connection

Overall requirements for safely connecting the boiler's electrical system.

4.14.1 General requirements

General safety and compliance requirements for electrical work.

4.14.2 Connection to the main supply

Steps for connecting the boiler to the mains electrical supply.

4.14.3 Electric board layout

Diagram illustrating the wiring connections on the electric control board.

4.15 Controls

Information on connecting and using external Vaillant controls and accessories.

4.15.1 Vaillant controls and accessories

List of compatible Vaillant controls and their connection methods.

4.16 Thermostatic radiator valves

Notes on using thermostatic radiator valves with the boiler.

4.17 Frost protection

Details on the boiler's integral frost protection feature.

4.18 Circulating pump

Information about the built-in circulating pump and its operation.

4.19 Anticycling ‘economiser’ control

Explanation of the control that prevents short cycling.

4.20 Automatic pump spin control (APS)

Description of the APS feature to prevent pump seizure.

5 Commissioning Part I

5.1 Preliminary electrical checks

Essential electrical safety checks before initial operation.

5.2 Gas supply

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

5.3 Cold water supply (ecoTEC combination boilers only)

Procedure for checking and purging the cold water supply.

5.4 Filling and bleeding the heating system

Procedure for filling and removing air from the heating system.

5.5 Initial system flush (“cold”)

Instructions for performing an initial cold flush of the heating system.

5.6 Filling the condensate siphon

Steps for filling the condensate siphon to ensure safety.

5.7 Adjusting the pumping capacity

Guidance on adjusting the pump speed for optimal heating system performance.

5.8 Adjusting the by-pass

Instructions for adjusting the boiler's automatic by-pass valve.

5.9 Checking the gas supply

Verification of gas inlet pressure and rate to ensure correct operation.

5.10 Refitting the case

Steps for securely refitting the boiler's front casing after servicing.

6 Functional checks (commissioning part II)

6.1 Functional checks

Overview of essential functional checks for the boiler.

6.1.1 Procedure

Steps for performing functional checks after installation and before handover.

6.1.2 Heating

Checking the heating operation and status display.

6.1.3 Water heating (combination boilers only)

Verifying the domestic hot water function for combination boilers.

6.1.4 Final flush of the heating system (“hot”)

Instructions for performing a final hot flush of the heating system.

6.2 Handing over to the user

Instructions for explaining boiler operation and maintenance to the end user.

7 Inspection and maintenance

7.1 Initial inspection

Recommendations for initial inspection and safety checks before maintenance.

7.1.1 Safety instructions

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

7.1.2 Maintenance

General procedures and checks to be performed during routine maintenance.

7.1.3 Overview of the inspection and maintenance tasks

A table summarizing annual inspection and maintenance tasks.

7.2 Servicing the burner module

Procedures for removing, cleaning, and refitting the burner module.

7.3 Cleaning the condensate siphon

Steps for cleaning the condensate siphon to maintain safety and function.

7.4 Checking the expansion vessel

Procedure for checking and adjusting the expansion vessel pressure.

7.5 Recommissioning the boiler

Steps to recommission the boiler after maintenance tasks.

7.6 Test operation

Checks to perform after completing any maintenance task.

8 Troubleshooting

8.1 Logical fault finding procedure

A systematic approach to diagnosing and resolving boiler faults.

8.1.1 Status codes

Explanation of the appliance's status codes displayed during operation.

8.1.2 Diagnostic codes

Information on accessing and interpreting diagnostic codes for advanced troubleshooting.

8.1.3 Fault codes

List of fault codes and their potential causes for quick identification.

8.1.4 Fault memory

Instructions for accessing and clearing the stored fault memory.

8.4 Test programs

Description of special test programs available for appliance functions.

8.5 Resetting parameter to factory settings

Procedure to reset adjustable parameters back to factory default.

9 Parts replacement

9.1 Safety instructions

Critical safety precautions to be followed before replacing any boiler components.

9.2 Replacing burner

Step-by-step guide for safely replacing the boiler burner.

9.3 Replacing fan or gas valve

Procedures for replacing the fan or the gas valve assembly.

9.4 Replacing expansion vessel

Instructions for safely replacing the boiler's expansion vessel.

9.5 Replacing primary heat exchanger

Step-by-step guide for safely replacing the primary heat exchanger.

9.6 Replacing electronics and display

Instructions for replacing the electronic control unit and display module.

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

Procedure for checking and adjusting CO2 levels for optimal combustion.

10 Recycling and disposal

Guidelines for the environmentally responsible disposal of the boiler and packaging.

11 Vaillant service

Information on recommended servicing and contacting Vaillant Service Solutions.

Appendix

EC declaration of conformity

Official statement confirming compliance with relevant EU directives.

PART 1 CONCENTRIC 60/100

REQUIREMENTS

Essential requirements for flue system installation, including regulations and standards.

Regulations and standards to be observed

Key regulations and standards that must be adhered to during installation.

PLANNING THE AIR/FLUE DUCT LAYOUT

Guidance on planning the layout of the air and flue duct system.

Alternative termination accessories available

Overview of available accessories for different flue termination types.

Maximum flue lengths for use with ecoTEC

Table detailing maximum permitted flue lengths for various ecoTEC models.

INSTALLING THE AIR/FLUE DUCT SLIDING SLEEVE

Instructions for installing the sliding sleeve to accommodate flue movement.

INSTALLATION OF THE HORIZONTAL AIR/FLUE DUCT

Procedures for installing horizontal air/flue duct systems.

Preparation

Initial steps for preparing the installation site for the horizontal flue duct.

Side flue installations

Guidance for installing horizontal flue ducts exiting to the side.

INSTALLATION OF THE VERTICAL AIR/FLUE DUCT

Instructions for installing vertical air/flue duct systems.

Pitched roof installation

Procedures for installing vertical flue ducts through pitched roofs.

Flat-roof installation

Steps for installing vertical flue ducts through flat roofs.

FITTING AIR/FLUE DUCT EXTENSIONS

Guidance on how to add extensions to the air/flue duct system.

How to add extensions

Detailed steps for measuring and cutting air/flue duct extensions.

How to install 2x 87° elbows

Instructions for installing 87-degree elbows in the air/flue duct system.

How to install 45° elbows

Instructions for installing 45-degree elbows in the air/flue duct system.

PART 2 CONCENTRIC 80/125

REQUIREMENTS

Essential requirements for flue system installation, including regulations and standards.

PLANNING THE AIR/FLUE DUCT LAYOUT

Guidance on planning the layout of the air and flue duct system.

Alternative termination accessories available

Overview of available accessories for different flue termination types.

Maximum flue lengths for use with ecoTEC

Table detailing maximum permitted flue lengths for various ecoTEC models.

CHANGING THE APPLIANCE CONNECTION-PIECE

Instructions for changing the appliance connection piece for different flue diameters.

INSTALLATION OF THE SLIDING SLEEVE

Procedures for installing the sliding sleeve for flue adjustment.

INSTALLATION OF THE HORIZONTAL AIR/FLUE DUCT

Procedures for installing horizontal air/flue duct systems.

Preparation

Initial steps for preparing the installation site for the horizontal flue duct.

Side flue installations

Guidance for installing horizontal flue ducts exiting to the side.

INSTALLATION OF THE HORIZONTAL AIR/FLUE DUCT Ø 80/125 WITH EXTENSIONS

Instructions for installing horizontal flue ducts with extensions.

INSTALLATION OF THE VERTICAL AIR/FLUE DUCT

Instructions for installing vertical air/flue duct systems.

Preparation

Initial steps for preparing the installation site for the vertical flue duct.

Pitched roof installation

Procedures for installing vertical flue ducts through pitched roofs.

Flat-roof installation

Steps for installing vertical flue ducts through flat roofs.

FITTING AIR/FLUE DUCT EXTENSIONS

Guidance on how to add extensions to the air/flue duct system.

How to add extensions

Detailed steps for measuring and cutting air/flue duct extensions.

How to install 2x 87° elbows

Instructions for installing 87-degree elbows in the air/flue duct system.

How to install 45° elbows

Instructions for installing 45-degree elbows in the air/flue duct system.

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Vaillant ecoTEC plus 637 User Manual

Table of Contents

Questions and Answers:

Vaillant ecoTEC plus 637 Specifications

Summary

1 Introduction

1.1 Notes on the documentation

1.2 Introduction

1.3 General Notes

1.4 CE marking

1.5 Gas council numbers

2 Boiler specifications

2.1 Technical data

2.2 Dimensions

2.4 Installation

2.5 Type plate

3 General requirements

3.1 Preliminary remarks for room sealed appliances

3.2 Related documents

3.3 Contents included with delivery

3.4 Installation site

3.5 Gas supply

3.6 Flue pipe

3.7 Flue termination

3.8 Air supply

3.9 Electrical supply

3.10 Guide to system requirements

3.11 Pump specifications

3.12 Condensate trap

4 Boiler installation sequence

4.1 Transporting the appliance

4.2 Required minimum distances/assembly clearances

4.3 Flue exit

4.4 Fitting the boiler hanging bracket

4.5 Installing the flue system

4.6 Fitting the boiler

4.7 Removing the front case

4.8 General instructions for heating system

4.9 Gas connection

4.10 Cold water mains inlet and hot water outlet

4.11 Condensate drain pipe

4.12 Heating connection

4.12.1 Heating flow and return connection

4.12.2 Pressure Relief Valve

4.13 Connecting the flue system to the boiler

4.14 Electrical connection

4.14.1 General requirements

4.14.2 Connection to the main supply

4.14.3 Electric board layout

4.15 Controls

4.15.1 Vaillant controls and accessories

4.16 Thermostatic radiator valves

4.17 Frost protection

4.18 Circulating pump

4.19 Anticycling ‘economiser’ control

4.20 Automatic pump spin control (APS)

5 Commissioning Part I

5.1 Preliminary electrical checks

5.2 Gas supply

5.3 Cold water supply (ecoTEC combination boilers only)

5.4 Filling and bleeding the heating system

5.5 Initial system flush (“cold”)

5.6 Filling the condensate siphon

5.7 Adjusting the pumping capacity

5.8 Adjusting the by-pass

5.9 Checking the gas supply

5.10 Refitting the case

6 Functional checks (commissioning part II)

6.1 Functional checks

6.1.1 Procedure

6.1.2 Heating

6.1.3 Water heating (combination boilers only)

6.1.4 Final flush of the heating system (“hot”)

6.2 Handing over to the user

7 Inspection and maintenance

7.1 Initial inspection

7.1.1 Safety instructions

7.1.2 Maintenance

7.1.3 Overview of the inspection and maintenance tasks

7.2 Servicing the burner module