Bosch Worcester FKT Series Installation Instructions Manual

The Bosch Worcester FKT Series comprises high-efficiency condensing boilers designed for residential heating and hot water applications. This manual provides essential information for the safe and correct installation, commissioning, and initial setup of the FKT boiler series. It covers pre-installation checks, system requirements, flue and gas connections, electrical wiring, filling and pressurizing the system, and initial firing. Adherence to these instructions, all applicable local codes, and regulations is mandatory.

Safety Information & Symbols

This section outlines critical safety warnings and explains the meaning of symbols used throughout the manual.

WARNING! Installation and service must be performed by a qualified installer, service agency, or gas supplier in accordance with all national and local codes. Failure to do so can result in fire, explosion, property damage, carbon monoxide poisoning, personal injury, or death.

Pre-Installation Checks

Before beginning installation, verify the following.

1. Boiler Model: Confirm the delivered FKT model matches the order and is suitable for the application (e.g., combi or system boiler).
2. Packaging: Inspect the boiler and all components for transport damage. Report any damage immediately.
3. Contents: Check against the packing list. Standard items include boiler unit, flue kit components, mounting jig (if applicable), condensate trap, installation/User instructions, and warranty card.
4. Site Suitability: Ensure the intended location meets all requirements for clearances, ventilation, flue routing, and access for service.
5. Existing System: For replacements, power flush the existing heating system to remove sludge and debris. Install a magnetic system filter.

Technical Specifications

• Models: FKT 1 Series (e.g., FKT130, FKT150).
• Type: Wall-mounted, condensing, fan-assisted boiler.
• Fuel: Natural Gas (G20) or LPG (G31). Refer to data badge.
• Efficiency: ErP seasonal space heating efficiency up to 94%.
• Output Range: Modulating from approx. 4 kW to maximum (e.g., 30kW, 35kW).
• Flow/Return Connections: 22mm or 28mm depending on model.
• Gas Inlet Connection: 22mm or 3/4" BSP female.
• Electrical Supply: 230V ~ 50Hz, 1A fuse. Must be connected via a fused spur with a 3mm contact separation.
• Flue System: Balanced flue (air intake/combustion exhaust). Specific concentric or twin pipe kits required.
• Max Operating Pressure: 3 bar. Pressure relief valve set to 3 bar.
• Dimensions & Weight: Approx. H720 x W400 x D300 mm, weight ~35kg.

Location & Clearances

The boiler must be installed on a sound, vertical wall capable of supporting its weight. It is rated IPX4D for bathroom installation (Zone 3 or outside zones).

Minimum Clearances (for servicing and ventilation):

• Top: 50 mm
• Sides: 5 mm
• Bottom (above worktop/cabinet): 300 mm
• Front (for door swing & access): 600 mm

⚠️ CAUTION! Do not install in areas prone to freezing, excessive dust, or where chemicals or aerosols are stored. The flue terminal must be positioned in accordance with the flue installation instructions (BS 5440-1) regarding distances from openings, corners, and boundaries.

System Water Requirements

The boiler requires a clean, inhibited sealed system.

1. Water Quality: Use clean, potable water. The system must be treated with a suitable corrosion inhibitor (e.g., Fernox F1, Sentinel X100) to BS 7593 standards.
2. System Cleanliness: Power flush the entire system prior to connection. Install a magnetic system filter (e.g., SpiroTrap) on the return pipework.
3. Expansion Vessel: The boiler contains an internal expansion vessel pre-charged to 1 bar. For larger systems, an additional external vessel may be required.

ℹ️ NOTE: Failure to ensure system cleanliness is the leading cause of heat exchanger failure and is not covered under warranty.

Flue & Air Supply Installation

The boiler uses a balanced flue system. Use only approved Worcester/Bosch flue components.

1. Planning: Plan the shortest, most direct route with a slight fall back to the boiler for condensate drainage.
2. Terminal Position: Install terminal respecting minimum distances: 300mm from an opening window/door, 600mm from a facing wall or boundary, 300mm above ground/balcony, and clear of any obstructions.
3. Assembly: Assemble flue components as per kit instructions, ensuring seals are fitted and joints are fully engaged and secured with screws.
4. Sealing: Where the flue passes through a wall or ceiling, seal the opening with non-combustible material to prevent ingress of combustion products into the building.
5. Inspection: After installation, perform a spillage test to verify integrity.

🔥 DANGER! Incorrect flue installation can lead to lethal carbon monoxide poisoning. Flue must be gas-tight.

Gas Supply Connection

1. Isolation: Ensure the gas supply is isolated.
2. Pipe Sizing: The gas pipe must be sized correctly for the boiler's maximum gas rate and the length of the run (refer to BS 6891).
3. Connection: Connect using a suitable gas-rated fitting to the 22mm/3/4" inlet on the boiler. Use jointing compound suitable for natural gas/LPG.
4. Testing: Perform a tightness test on the complete installation, including the boiler gas valve, in accordance with regulations.
5. Gas Rate Check: Upon commissioning, check the gas rate (meter test) to ensure correct operation and input.

🛠️ QUALIFIED PERSONNEL: Gas connection and testing must be performed by a Gas Safe Registered engineer (UK).

Electrical Connection

⚡ DANGER! DISCONNECT POWER BEFORE MAKING CONNECTIONS.

1. Supply: Provide a permanent 230V 50Hz supply via a double-pole fused spur with a 3A fuse, located adjacent to the boiler.
2. Wiring: Connect the supply (L, N, E) to the boiler's terminal block as per the wiring diagram inside the boiler casing.
3. External Controls: Connect room thermostat, programmers, etc., to the low voltage terminals provided. Refer to the wiring guide for S-Plan, Y-Plan, etc.
4. Pump Overrun: The boiler manages the pump overrun internally; no external wiring is needed for this function.
5. Earth Bonding: Ensure all metallic pipework is bonded in accordance with IET Wiring Regulations (BS 7671).

Hydraulic Connections

Connect heating flow, return, and (for combi models) cold water inlet and hot water outlet.

⚠️ CAUTION! Use appropriate sealant (e.g., PTFE tape) on all threaded connections. Ensure all isolation valves are accessible.

Filling, Pressurizing & Venting

1. Filling Loop: Connect the temporary filling loop (if not integrated) between the cold water inlet and heating return. Open both valves slowly.
2. System Pressure: Watch the pressure gauge on the boiler front. Fill to 1.0 - 1.5 bar cold.
3. Venting: Vent all air from the system using manual vents on radiators and the automatic air vent within the boiler (if accessible).
4. Final Pressure: Close filling loop valves and remove the loop (if temporary). Check for leaks. The pressure will rise when the system is hot (typically to around 2 bar).
5. Condensate Trap: Prime the condensate trap by pouring water into the boiler sump as per instructions.

Commissioning & Initial Start-Up

1. Pre-Start Checks: Verify gas and electrical connections are tight, system is filled and vented, flue is secure, and condensate pipe is clear.
2. Power On: Switch on electrical supply. The boiler display may show codes or initiate a self-test.
3. Gas Purge: Follow the boiler's specific purge sequence as indicated in the display or manual to remove air from the gas line.
4. Initial Firing: Set a demand for heating or hot water. The boiler should ignite. Listen for correct fan and burner operation.
5. Measurements: Check gas rate, combustion performance (CO2 ratio) using a flue gas analyzer. Adjust if necessary per manual.
6. Function Test: Test all modes (heating, DHW), check pump operation, thermostat response, and safety devices (overheat stat).
7. Benchmark: Complete the Benchmark Commissioning Checklist in the back of the installation manual. Leave one copy with the customer and keep one for your records.

User Briefing & Handover

Before leaving the installation, brief the user on the following:

• How to turn the boiler on/off.
• How to adjust heating temperature and hot water temperature (via controls or boiler interface).
• How to read the pressure gauge and repressurize the system using the filling loop (if accessible to user).
• What the fault code display means and basic reset procedure.
• The importance of annual servicing by a qualified engineer.
• Location of the main gas shut-off valve and electrical isolation point.

Handover Documents: Provide the User Instructions, completed Benchmark Checklist, and warranty registration information to the customer.