EHC Fusion MERCURY COMBI

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Summary

Preparation and Building Regulations

Instructions and Building Regulations

Details installation requirements and relevant building standards like BS EN series.

Boiler Location and Clearances

Specifies optimal placement and necessary clearances for boiler installation.

Installation Procedures

General Installation Requirements

Covers qualified installers, pipe connections, case removal, isolation valves, water inlet, and air vents.

System Design and Installation Considerations

Includes boiler sizing, insulation, system design, flushing, pressures, and types.

Hanging and Final Connections

Instructions for physically hanging the boiler and connecting to the heating system.

Boiler Dimensions & Plumbing Schematic

Boiler Dimensions

Provides physical dimensions and clearance requirements for the boiler unit.

Plumbing Schematic Overview

Illustrates the system's water connections and component layout.

Commissioning and System Protection

DHW Pipework Bleeding

Procedure for bleeding air from the domestic hot water pipework.

Filling the Heating Circuit

Steps for filling the central heating system and purging air.

System Protection and Cleaning

Recommendations for system flushing and chemical treatment using Fernox products.

Electrical Connections & Controls

Electrical Safety and Regulations

Adherence to IEE BS7671, earthing, RCD/MCB requirements, and qualified electrician.

Boiler Protection and External Controls

Recommended electrical protection levels and integration with external controls.

Mains Connection Diagram

Diagram illustrating the main electrical power supply connection to the boiler.

Boiler Internal Layout

Internal Component Identification

Diagram and key identifying all internal parts of the boiler.

Wiring Diagrams: Control Panel & External

Control Panel Wiring Details

Diagrams for volt-free control panel connections, including optional sensors.

External Wiring Schematics

Illustrates the external electrical connections required for the boiler system.

Internal Boiler Wiring (12;15 kW)

Wiring Components and Connections

Key and schematic detailing internal wiring for 12/15 kW models.

Internal Boiler Wiring (19;26 kW)

Wiring Components and Connections

Key and schematic detailing internal wiring for 19/26 kW models.

User Instructions and Control Panel Operation

Control Panel Overview and Indicators

Key to control panel buttons, indicators, and their status meanings.

Boiler Start-up and Operation Modes

Steps for initial boiler start-up and details on stand-by, winter, and summer modes.

Advanced Settings and Configuration

Weather Compensation and Curve Settings

Configuration of weather compensation, curve coefficient, and offset.

Pump, Pressure and Temperature Settings

Adjusting pump modes, pressure, sensor settings, and max CH temperature.

Consumption History

Read-only display of the boiler's kilowatt consumption history.

Fault Finding Guide

Common Faults, Reasons, and Actions

Table detailing common symptoms, their causes, and recommended actions for troubleshooting.

Technical Specifications

Boiler Performance and Dimensions

Details on output, dimensions, electrical supply, and safety class.

Water Heater and System Details

Specifications for water heater efficiency, water mains pressure, and water hardness.

This document serves as the Installation and Technical Manual for the Fusion Range of Boilers, specifically the Mercury Combi model, manufactured by The Electric Heating Company (EHC). It provides comprehensive instructions for the installation, operation, and maintenance of these electric boilers, which are designed as a central heating solution.

Function Description

The Fusion Mercury Combi Boiler is an electric heating appliance designed to provide central heating and domestic hot water. It operates by heating water electrically, circulating it through a closed system to radiators or underfloor heating, and also supplying hot water on demand. The boiler is equipped with a control panel that allows users to manage heating parameters, monitor system status, and troubleshoot potential issues. It is suitable for both domestic and commercial properties, offering a versatile solution for various heating designs, including underfloor systems. The boiler integrates an auto air vent and is designed to work with external controls such as programmers and room thermostats to optimize energy efficiency and comfort.

Usage Features

The boiler's operation is managed through a user-friendly control panel, which includes a digital display and control buttons. Users can switch between Stand-by, Winter, and Summer modes. In Stand-by mode, the pump activates daily for two minutes to prevent seizure. Winter mode enables both central heating and domestic hot water functions, displaying current flow temperature and allowing adjustments to domestic water temperature settings. Summer mode focuses solely on domestic hot water, with the central heating function inactive.

The control panel provides real-time feedback through various indicators:

Room Thermostat/Heating Activity (CH) Indicator: Shows if the room thermostat is calling for heat, if the required temperature has been reached, or if the master appliance is preventing heating.
Pump and Flow Activity Indicator: Indicates if the pump is active and if there is a proper flow rate. It flickers to signal a lack of flow or insufficient flow rate, which can lead to heating element shutdown.
Weather Compensation Controller Indicator: Lights up when weather compensation is active and flashes if the outside sensor is faulty or unable to determine installation temperature.
Inlet and Outlet Temperature Indicators: Display the temperature of water entering and leaving the boiler.
Instantaneous Water Heater Indicator: Shows when the device is operating in domestic hot water heating mode.
Pressure Indicator: Displays the system pressure in bars. A flickering indicator signifies insufficient pressure (below 0.5 bar), which will block heating.
Digital Display: Shows temperature in °C, power in kW, flow in l/min, and error codes.

Advanced settings allow for customization of the heating curve coefficient and offset, pump working mode (automatic or constant operation), pump efficiency (head), and CH pressure sensor activation. These settings enable users to fine-tune the boiler's performance to match their specific installation and preferences. The boiler also features an external weather sensor input, which, if used, allows for weather compensation to adjust heating output based on outdoor temperatures. If not used, this feature must be disabled in the advanced settings.

Maintenance Features

Proper installation and regular maintenance are crucial for the boiler's longevity and reliable operation. The manual emphasizes several key maintenance aspects:

System Flushing: Before commissioning, the heating circuit must be thoroughly flushed to remove debris and contaminants. This is a critical step to prevent boiler failure and maintain warranty validity. The process involves filling, draining, and refilling the system with a cleaner (e.g., Fernox F3) and then an inhibitor (e.g., Fernox F1). TDS readings should be within 10% of mains ppm value after flushing.
Water Softener: In hard water areas, a water softener must be used to prevent scale formation, although salt softeners should not be used to fill the heating system.
Inhibitor Levels: Inhibitor levels should be checked annually, typically during service, or sooner if the system content is lost, using a Fernox inhibitor Test Kit.
Pipework Insulation: Insulating all pipework, especially within a boiler cupboard, is recommended to reduce heat loss and prevent high cupboard temperatures.
Drain Valves: Drain valves should be fitted at the lowest point of the system pipework for easy draining during maintenance.
Magnetic Filter: The boiler should be connected to a heating system equipped with full bore isolation valves and an external magnetic filter to protect against debris.
Fault Finding: The manual includes a detailed fault-finding section that correlates indicator statuses (e.g., flickering pressure indicator, lack of flow indicator) with potential reasons (e.g., insufficient pressure, pump blockage, sensor failure) and recommended actions (e.g., increase pressure, unblock pump, contact authorized service). This allows users or technicians to quickly diagnose and address common issues.
Professional Servicing: All electrical connections and major repairs must be carried out by a fully qualified electrician or heating engineer. The manufacturer will not be held responsible for faulty installations performed by unqualified tradespeople.
Warranty: The boiler comes with a 24-month warranty covering defects from faulty materials and workmanship. However, the warranty does not cover water leaks into the boiler or damage from poor or incorrect installation. Product registration is encouraged via the EHC website.