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Need help?Do you have a question about the Worcester Greenstar Si Compact Series and is the answer not in the manual?
Outlines critical safety rules for gas leaks, boiler operation, materials, and cleaning.
Explains boiler screen symbols and their meanings.
Guides on identifying alerts, fault codes, and performing a boiler reset procedure.
Provides a table listing common boiler problems, their causes, and recommended remedies.
Addresses problems related to freezing condensate pipes and safe thawing procedures.
Explains support services for breakdowns, warranty conditions, and contact information for assistance.
This document provides user instructions for the Wall Hung RSF Gas Fired Condensing Combination Boiler, specifically the Greenstar Si Compact model, designed for sealed central heating systems and mains-fed domestic hot water. It is applicable in the UK/IE and must be followed unless superseded by statutory obligations.
The boiler is manufactured by Worcester, Bosch Group, a company that prides itself on manufacturing boilers to strict quality control standards. The Greenstar range is highlighted for its energy efficiency, economical running costs, and value for money, achieving a SEDBUK 2005 Band A rating. The product comes with a 2-year parts and labor guarantee, with an optional complete maintenance scheme called Worcester Total Cover.
The Greenstar Si Compact is a gas-fired condensing combination boiler that provides both central heating and domestic hot water. It operates in various modes to optimize energy consumption and user comfort.
When the boiler is not actively supplying central heating or hot water, the display shows the internal temperature and is not backlit. When a heat demand occurs, the flame symbol will appear, indicating the boiler is firing up.
The central heating temperature control knob allows users to set the desired flow temperature between 30 and 82°C. This temperature is displayed digitally and refers to the flow temperature through the radiators, not the room temperature. The "e" point on the control provides guidance for maximum temperature setting for optimum energy efficiency. The radiator symbol confirms that the central heating setting is being changed. After five seconds of inactivity or by pressing "ok," the display returns to the default screen. Room comfort levels should be managed using thermostatic radiator valves and/or a room thermostat.
For unoccupied properties during cold weather, it is recommended to leave the programmer on constant and the room thermostat set to 15°C.
To turn off central heating, set the programmer/timer to the off position. Refer to the programmer/timer manufacturer's instructions for specific guidance.
The hot water temperature control knob allows users to set the desired temperature between 40 and 60°C, which is shown on the digital display. The tap symbol confirms that the domestic hot water setting is being changed. After five seconds of inactivity or by pressing "ok," the display returns to the default screen.
By default, the hot water heat exchanger is kept pre-heated to reduce the time needed to deliver hot water. "PreHeat" is displayed when this function is active. To save energy, if there is no hot water demand for 24 hours, the boiler will suspend PreHeat until a new demand occurs, at which point it reactivates.
Eco mode is an energy-saving feature that disables the Pre-heat function. To activate, press and hold the "eco" button for at least four seconds. "Eco" will be displayed, indicating the mode is active. In Eco mode, less energy is used, but there will be a slightly longer wait for hot water. To exit Eco mode and return to PreHeat, press and hold "eco" for at least four seconds.
If a twin-channel programmer is fitted, the PreHeat/Eco option can be selected via the programmer. Eco mode timed by a programmer will be displayed as shown in the manual, and users should refer to the programmer manual for setting time periods.
In case of an alert, a fault code and an alert symbol will be displayed on the boiler, and the blue operation/fault light will flash. Users should refer to the Fault Finding section in the manual or press "reset" to clear the problem.
To reset the boiler, press the "reset" button. "Reset" and a tick mark will be briefly displayed. If successful, the boiler returns to normal operation. If unsuccessful, the alert code will reappear, and the blue operation/fault light will continue to flash. If the fault persists, contact Worcester, Bosch Group.
To further enhance energy saving in stand-by mode, the blue operation/fault diagnostic light can be deactivated. It will still flash for faults but will not activate during a heat demand. Users should ask their installer to set up this feature.
The boiler is connected to a pre-pressurized sealed heating system. Users should regularly check the pressure gauge. If the pressure reads less than 1 bar, the system needs re-charging. A permanent significant decrease or increase in pressure requires contacting an installer or maintenance engineer. There are three types of filling methods:
The outer painted metal case of the boiler should be cleaned with a damp, soft cloth. Chemical or abrasive materials should not be used.
The boiler must be serviced regularly by a competent, qualified person (e.g., a Worcester service engineer or Gas Safe registered engineer) to maintain efficiency, safety, and reliability. Original spares should always be used. The Service Record in the Benchmark Checklist must be completed after each service and is required for guarantee work and by local Building Control Inspectors.
The Benchmark initiative promotes correct installation, commissioning, and servicing of domestic central heating boilers. A "checklist" provided with every boiler must be completed by the installer to confirm adherence to manufacturer's instructions. This document also serves as a logbook for recording regular servicing, which can be valuable for future property sales.
Adequate space must be provided around the boiler for safety and servicing access. This space should not be restricted by cupboards, shelves, or other additions to prevent overheating.
To ensure maximum working life and peak efficiency, the boiler requires regular servicing and maintenance checks by a competent person beyond the initial two-year guarantee period. If the boiler malfunctions or needs servicing, contact the Worcester, Bosch Group Appointments Team. The Gas Council number and boiler details can be found on the front cover of the User Instructions and the boiler identification label.
The manual provides a table of common problems, causes, and remedies. If the boiler stops functioning or performs unexpectedly, users can perform simple checks. For persistent problems or other alert codes, contact Worcester, Bosch Group. When calling, it is helpful to provide the alert code and three-digit number (e.g., EA and 227).
Condensate pipework run externally or in unheated areas is at risk of freezing. A frozen pipe will cause the boiler to shut down. Users can attempt to thaw accessible ground-level pipes by applying a hot water bottle, microwaveable heating pack, or a cloth soaked in hot (not boiling) water. After thawing, the boiler must be reset by pressing the reset button for five seconds. If it does not restart, contact Worcester, Bosch Group. Never attempt to thaw pipes at height or use boiling water.
Worcester, Bosch Group supports this boiler in the UK and Eire with specialist service engineers. Invoices for third-party repair work will not be accepted. No charge is made for parts/labor if a boiler fault is found within the guarantee period and evidence (e.g., Benchmark Checklist) is provided. A call-out charge applies if the boiler is out of guarantee, if the first-year service inspection is not documented, if no fault is found, or if the breakdown is due to misuse or issues with other plumbing/heating system parts not supplied by Worcester, Bosch Group. For suspected faults, refer to the fault-finding section. For boiler faults or breakdowns, contact the Worcester, Bosch Group appointments team.
Worcester, Bosch Group prioritizes environmental protection. All Greenstar gas boilers are 100% recyclable. Packaging materials are environmentally compatible and recyclable. Assemblies can be easily dismantled and sorted for recycling.
The boiler comes with a two-year guarantee against faulty materials or workmanship from the installation date, subject to terms and conditions. Bosch Thermotechnology Ltd. will exchange or repair faulty components free of charge. Users may need to prove the installation date, correct commissioning, and first-year service (documented in the Benchmark Checklist). The boiler must be used for normal domestic purposes. The guarantee does not affect statutory rights. Guarantee registration can be done online or by phone. Users should ensure the Benchmark Checklist is completed by their installer or service engineer.
General| Fuel Type | Natural Gas |
|---|---|
| Efficiency Rating | A |
| Dimensions (HxWxD) | 690 x 390 x 280 mm |
| Mounting | Wall-mounted |
| Model | Greenstar 25Si Compact |
| Type | Combi |
| Warranty | 5 years |
| Hot Water Flow Rate | 10.2 L/min |
| Efficiency | Up to 94% |
