Worcester FKS Series Installation Instructions Manual

The Worcester FKS Series is a range of high-efficiency condensing boilers designed for residential and light commercial applications. These boilers feature advanced modulating burners, stainless steel heat exchangers, integrated weather compensation, compatibility with smart heating controls, and a compact design for easy installation. Below are key sections for safety, technical specifications, installation procedures, commissioning, operation, and maintenance.

Features at a Glance

Key components: Stainless steel condensing heat exchanger, modulating fan-assisted burner, integrated pump, expansion vessel, pressure gauge, control panel with LCD display, and multiple system connection terminals.

Pre-Installation Requirements

Before installation, ensure the location and system meet all requirements.

1. Location: Must be installed on a suitable load-bearing wall in a well-ventilated area (e.g., kitchen, utility room, garage). Maintain clearances as specified.
2. Gas Supply: Verify correct gas type (Natural Gas or LPG) and pressure. Install an accessible gas isolation valve.
3. Water Quality: System must be clean and treated with inhibitor. Magnetic filter strongly recommended.
4. Electrical Supply: 230V ~ 50Hz fused spur required near boiler.
5. Flue Route: Plan flue route ensuring compliance with regulations regarding terminals and distances from openings.

WARNING! Installation must comply with local building regulations, gas safety regulations, and be performed by a qualified and registered installer.

Installation Procedure

Follow these steps in sequence for safe and correct installation.

1. Mounting: Fix mounting bracket to wall using supplied fixings, ensuring it is level.
2. Flue Installation: Assemble and install flue kit according to instructions, ensuring seals are fitted and joints are secure. Terminal must be in a permissible location.
3. Water Connections: Connect heating flow, return, and (if combi) cold mains and hot water outlets using appropriate fittings. Fit isolation valves.
4. Gas Connection: Connect gas supply pipe to boiler gas inlet using suitable pipe and compound. Test for leaks.
5. Condensate Drain: Connect condensate trap outlet to a suitable drain using 22mm plastic pipe. Ensure a fall of at least 2.5°.
6. Electrical Connection: Connect mains supply, pump live, and any external controls (room stat, programmer) to the terminal block as per wiring diagram.
7. Hang Boiler: Lift boiler onto bracket and secure.

CAUTION! Boiler is heavy; use two people for lifting. Do not use the case or controls as lifting points.

Technical Specifications

• Models: FKS 24, FKS 30, FKS 36.
• Output (Heating): 24kW, 30kW, 36kW (modulating).
• Efficiency (ErP): Up to 94% (seasonal).
• Gas Types: G20 Natural Gas (20 mbar), G31 Propane (37 mbar).
• Water Connections: Heating: 22mm; Combi Mains: 15mm; Hot Water Outlet: 15mm.
• Max Working Pressure: 3 bar.
• Expansion Vessel: 8 litre pre-charge (1 bar).
• Electrical Supply: 230V ~ 50Hz, 1A fuse.
• Dimensions (HxWxD): 720mm x 400mm x 300mm (approx).
• Flue Diameters: Concentric: 60/100mm; Twin Pipe: 60mm.

System Wiring & Connections

Electrical connections must be made with the power supply isolated.

Terminal Block (Typical): L (Live), N (Neutral), E (Earth), Pump Live, External Controls (Room Stat, Programmer), OpenTherm +/-.

1. Connect permanent Live and Neutral from fused spur to L and N.
2. Connect Earth to terminal E.
3. Connect external room thermostat/programmer switched live to appropriate terminals (e.g., RT).
4. For pump overrun, connect pump live wire from boiler to external pump (if not using internal pump).
5. For OpenTherm controls, connect to dedicated +/- terminals.

Tip: Refer to the specific wiring diagram supplied with the boiler model. All wiring must comply with IET Wiring Regulations (BS 7671).

Flue & Air Supply

Correct flue installation is critical for safe operation.

1. Type: Use only approved Worcester flue kits. Options: horizontal, vertical, or extended lengths.
2. Routing: Maximum permissible length as per manual. Support at intervals. Avoid running through unheated spaces without insulation.
3. Terminal Position: Must be at least 300mm from any opening, window, or air vent. Clear of obstructions like gutters.
4. Sealing: Ensure all internal and external seals are fitted. Joints must be fully engaged and secured with screws.
5. Air Supply: For room-sealed operation, ensure air inlet path is unobstructed. For open-flue configurations (if applicable), ensure adequate permanent ventilation in the room.

WARNING! An incorrectly installed flue can lead to production of lethal carbon monoxide. Always perform a spillage test after installation.

Water System Connections

Ensure all water connections are pressure-tight and correctly sized.

1. Heating Flow & Return: Marked on boiler. Use 22mm pipe for connections close to boiler. Fit isolating valves.
2. Filling Loop: Connect temporary or permanent filling loop between cold mains and heating return, with double-check valves.
3. Pressure Relief Valve: Discharge pipe must be 15mm copper, run to a safe visible discharge point, with continuous fall.
4. Condensate Drain: Must be run in 22mm plastic pipe to internal drain (e.g., sink waste) or external soakaway. Protect from freezing if external.
5. Magnetic Filter: Strongly recommended on heating return to protect heat exchanger.

CAUTION! Do not use jointing compounds on plastic components (e.g., condensate trap). Use PTFE tape on threaded metal fittings only.

Commissioning & Initial Start-Up

After installation, complete these steps before handing over to the customer.

1. Fill & Purge: Fill system to 1.0 - 1.5 bar cold. Purge all air from radiators and pump.
2. Gas Rate Check: Turn on gas supply. Check gas pressure at inlet and burner pressure. Perform gas rate calculation to confirm correct input.
3. Flue Spillage Test: With boiler running, test for spillage at the draught diverter (if applicable) using smoke match or analyser probe.
4. Combustion Analysis: Use a flue gas analyser to measure CO/CO2 ratio and efficiency. Adjust if necessary (qualified installers only).
5. Set Controls: Configure boiler parameters via control panel (e.g., maximum output, pump settings, weather compensation curve).
6. Customer Demonstration: Show user how to operate basic controls, reset boiler, and read pressure gauge.

Record: Complete Benchmark Commissioning Checklist and leave with user.

User Controls & Settings

Basic operation via the front control panel.

Control Panel: On/Off button, Menu Navigation buttons (+/-), OK button, Reset (R) button, LCD display.

Basic Operation: Press On/Off to start. Use +/- to adjust heating temperature. Display shows current flow temperature, pressure, and status.

Menu Settings (Installer Level): Access by holding two buttons (e.g., + and -). Settings include: Max CH output, Pump mode (constant, proportional), Weather compensation curve, DHW temperature (combi), Clock, Fault history.

Resetting: To clear a lockout fault, press the (R) reset button for 3 seconds.

Maintenance Schedule

Annual servicing by a qualified engineer is essential for safety, efficiency, and warranty.

1. Visual Inspection: Check for leaks, corrosion, and integrity of flue.
2. Clean Heat Exchanger: Remove and clean condensate trap. Inspect and clean primary heat exchanger if necessary.
3. Clean Burner & Fan: Remove and clean burner assembly and fan.
4. Check Ignition & Flame Sense Electrodes: Clean and set gap.
5. Check Safety Devices: Test operation of overheat thermostat and pressure relief valve.
6. Combustion Check: Perform flue gas analysis and adjust if needed.
7. System Check: Check inhibitor concentration, clean magnetic filter, top up pressure.

CAUTION! Isolate gas and electrical supplies before any maintenance. Use only genuine Worcester spare parts.

Troubleshooting & Error Codes

Reset: For lockout faults, press reset (R) button after addressing cause.

Service & Support: For technical assistance, contact Worcester Bosch Technical Helpline or consult your installer. Register the warranty online.