Product Overview

The Worcester Greenstar 28i Junior is a wall‑mounted, gas‑fired condensing combi boiler delivering efficient heating and hot water. It supports natural gas or LPG, features a sealed central heating system, and complies with UK/IE standards for safe, reliable operation. For 24/7 heating & hot water.!!

Safety Warnings

Before installing the Worcester Greenstar 28i Junior, read all safety instructions. The unit uses natural gas or LPG; improper handling can cause fire or explosion. Ensure the gas supply is shut off before any work. Verify the gas pressure is within the manufacturer’s specified range (0.4–1.2 bar for natural gas, 0.3–0.8 bar for LPG). Use only approved, licensed gas fittings and check for leaks with a suitable detector. The boiler must be mounted on a stable, fire‑resistant and wall, with a minimum and a clearance a of 300 mm from any combustible material. Install a dedicated, properly sized electrical 30 A circuit; avoidand using the main supply. The water supply should be fitted with a pressure‑reducing valve and a non‑return valve to prevent backflow. The boiler’s condensate drain must be directed to a suitable disposal point, not into the drainage system. Keep the combustion chamber and flue clear of obstructions; do not block the exhaust outlet. Never operate the boiler with the cover removed or with the unit in an enclosed space. Ensure ventilation let CO₂ to escape; install a CO detector in the room. The unit must be commissioned by a registered engineer who will perform pressure tests, gas leak checks, and verify the flue is correctly installed. Do not attempt to repair or modify the boiler yourself. Follow all local regulations and obtain necessary permits. Failure to comply can result in injury, property damage, or legal penalties.

Installation Prerequisites

Before mounting the Worcester Greenstar 28i Junior, verify that the wall is capable of supporting the unit’s weight and that the wall material is fire‑resistant. The mounting bracket must be fixed to a solid stud or reinforced block with at least two 12 mm screws. Ensure the wall is level; use a level and adjust the bracket until the unit will sit flush. The boiler requires a clearance of 300 mm on all sides to allow airflow and maintenance access. Check that the room has ventilation and that the flue outlet is positioned at least 1 m above any door or window to prevent backdraft. The gas supply line must be connected to a certified gas valve, with the gas pressure set to the manufacturer’s range (0.4–1.2 bar for natural gas, 0.3–0.8 bar for LPG). Use only approved fittings and check for leaks with a gas detector before energising the unit. The electrical connection should be made on a dedicated 30 A circuit, isolated from the main supply, and must comply with the latest wiring regulations. The water supply line should be fitted with a pressure‑reducing valve set to 1.5–2.5 bar, and a non‑return valve to prevent backflow. Condensate must be drained to a suitable discharge point, not into the domestic drainage system. All fittings should be tightened to the manufacturer’s torque specifications. Finally, confirm that the room meets the minimum temperature requirement for safe operation and that the boiler is positioned away from any heat‑sensitive equipment or flammable materials. Once all prerequisites are satisfied, the installation can proceed to the mounting procedure.

Before mounting the Worcester Greenstar 28i Junior, verify that the wall is capable of supporting the unit’s weight and that the wall material is fire‑resistant. The mounting bracket must be fixed to a solid stud or reinforced block with the supplied 12 mm screws, ensuring the bracket is level. The boiler requires a clearance of 300 mm on all sides to allow airflow and maintenance access. Check that the room has ventilation and that the flue outlet is positioned at least 1 m above any door or window to prevent backdraft. The gas supply line must be connected to a certified gas valve, with the gas pressure set to the manufacturer’s range (0.4–1.2 bar for natural gas, 0.3–0.8 bar for LPG). Use only approved fittings and check for leaks with a gas detector before energising the unit. The electrical connection should be made on a dedicated 30 A circuit, isolated from the main supply, and must comply with the latest wiring regulations. The water supply line should be fitted with a pressure‑reducing valve set to 1.5–2.5 bar, and a non‑return valve to prevent backflow. Condensate must be drained to a suitable discharge point, not into the domestic drainage system. All fittings should be tightened to the manufacturer’s torque specifications. Finally, confirm that the room meets the minimum temperature requirement for safe operation and that the boiler is positioned away from any heat‑sensitive equipment or flammable materials. Once all prerequisites are satisfied, the installation can proceed to the mounting procedure.

Natural Gas Connection

The Worcester Greenstar 28i Junior is designed for use with natural gas, complying with UK/IE gas safety standards. Prior to connecting the gas supply, ensure the gas mains pressure is within the manufacturer’s specified range of 0.4 bar to 1.2 bar. Use a pressure‑reducing regulator if the mains pressure exceeds the upper limit. The gas line should be routed along the wall, avoiding sharp bends and any heat‑generating equipment. All fittings must be of the correct size and made from approved materials, typically 1/2‑inch copper or stainless steel. The gas valve should be a certified, single‑acting valve with a lock‑out feature, and it must be installed on the side of the boiler that allows the gas flow to be shut off independently of the main supply. Connect the regulator to the valve, then run the line to the boiler’s inlet, ensuring a 90‑degree bend at the connection point to prevent backflow. Tighten all joints to the manufacturer’s torque specification, usually 10 Nm for copper fittings. After the line is connected, perform a leak test by applying a soapy water solution to all joints and checking for bubbles. If bubbles appear, tighten the joint further or replace the fitting. Once the leak test is passed, close the gas valve and allow the regulator to stabilize for at least 5 minutes before energising the boiler. The boiler’s internal safety interlocks will verify the gas flow and pressure before ignition. The system should be tested by a qualified gas engineer, who will confirm that the gas pressure, flow rate, and safety valves are all functioning within the specified parameters. Only after this certification should the boiler be commissioned for use. Proper gas connection ensures safe, efficient operation and compliance with local regulations, protecting both the household and the environment. The gas supply line should be insulated where it passes through cold areas to prevent condensation. The regulator should be installed at the point of entry to the boiler to maintain a stable pressure regardless of fluctuations in the mains supply. The boiler’s internal gas pressure sensor will automatically adjust the regulator if the pressure falls below the minimum threshold, ensuring consistent combustion. The manufacturer recommends using a 1/2‑inch copper pipe with a 90‑degree elbow at the inlet to reduce turbulence. All connections should be checked for tightness after the boiler has been in operation for 24 hours, as thermal expansion can loosen fittings. The gas line must be routed away from the water supply to avoid cross‑contamination. A dedicated gas isolation valve should be installed between the regulator and the boiler, allowing the boiler to be shut off without affecting the rest of the household supply. Finally, the boiler’s combustion chamber should be inspected for proper clearance and ventilation, as inadequate airflow can lead to incomplete combustion and CO buildup. The installation should be carried out by a gas‑licensed engineer, who will also provide a certificate of compliance in accordance with the Gas Safety (Installation and Use) Regulations 1998. The regulator’s pressure gauge should be calibrated annually to ensure accurate readings. The boiler’s safety interlock will shut down the gas supply if the pressure drops below 0.3 bar, protecting against flame failure. The manufacturer specifies that the gas line should be free of any kinks or sharp bends that could restrict flow. The gas valve should be positioned at a height of 1.2 m from the floor for easy access during maintenance. All gas fittings should be greased with a suitable lubricant to prevent corrosion over time. The boiler’s manual provides a detailed diagram of the gas piping layout, which should be followed precisely to avoid misrouting. The gas connection should be tested at the end of the installation process by a certified engineer, who will record the pressure, flow rate, and any anomalies in a logbook. This logbook must be retained for future reference and for compliance with local regulatory bodies.

LPG Connection

The Worcester Greenstar 28i Junior can operate on LPG (C13, C33, C53). Install the regulator at the boiler entry and run the inlet pipe with a 90‑degree elbow to minimise turbulence. All fittings must be of the correct size and made from approved materials; the gas valve should be a single‑acting, lock‑out valve that can be shut off independently of the mains supply. Perform a leak test with a soapy water solution on all joints; any bubbles indicate a leak that must be tightened or replaced. Once the leak test is passed, close the gas valve, allow the regulator to stabilise for at least 5 minutes, and then energise the boiler. The boiler’s internal safety interlocks will verify the gas flow and pressure before ignition. Check LPG pressure against the manufacturer’s specification of 0.4 bar to 1.2 bar; if the pressure is too high, use a pressure‑reducing regulator. Calibrate the regulator’s gauge annually. Install a dedicated gas isolation valve between the regulator and the boiler, allowing the boiler to be shut off without affecting the rest of the household supply. Position the gas valve at a height of 1.2 m from the floor for easy access during maintenance. Follow the boiler’s manual diagram of the gas piping layout precisely. Test the gas connection at the end of installation by a certified engineer, who will record the pressure, flow rate, and any anomalies in a logbook. Retain this logbook for future reference and regulatory compliance. All procedures must be performed by a licensed professional to ensure safety and compliance.

Electrical Connection

Connect the boiler to a dedicated 230 V single‑phase supply with a 16 A circuit breaker or fuse. The wiring must use 1.5 mm² copper cable, fully insulated, and routed through a conduit or cable tray. The boiler’s 3‑pin plug is fitted to the supply, ensuring the earth pin engages the earth connection. A separate isolation switch should be installed between the supply and the boiler, allowing the unit to be shut off without affecting the rest of the household. The boiler’s internal circuit must be protected by a 16 A over‑current protection device, and a residual‑current device (RCD) of 30 mA should be used if the boiler is in a damp or wet location. The earth connection is required to be bonded to the main earth bus of the building. All connections should be tightened to the manufacturer’s torque specifications, and all terminals must be free of corrosion. After wiring, perform a continuity test between the earth and the boiler chassis, and a resistance test to confirm the earth resistance is below 1 Ω. Finally, a qualified electrician should verify that the boiler’s control board receives the correct voltage and that the safety interlocks are functioning. Document the wiring diagram and test results in the installation logbook for future reference. All cable terminations must be secured with cable clamps and the cable entry points should be sealed with appropriate gaskets to prevent ingress of moisture. The boiler’s control panel must be inspected to ensure the power indicator lights are functioning and that the RCD trips within the specified time. The installation should be inspected by a registered engineer, who will verify compliance with the latest wiring regulations and provide a signed certificate. The boiler should be positioned at least 0.5 m above the floor to allow for ventilation and to prevent water ingress. The wiring conduit should be routed along the shortest path to the boiler, avoiding sharp bends that could damage the cable. All connections must be double‑checked for tightness and the cable should be free of kinks. The final test should include a voltage check at the boiler terminals and a short‑circuit test to confirm the protective devices are working. The boiler’s power supply should be isolated from any other electrical equipment to prevent interference. A dedicated circuit breaker should be installed in the consumer unit, and the breaker must be labeled clearly as ‘Greenstar 28i Junior’. The wiring should be color‑coded according to the national standard: brown for live, blue for neutral, and green/yellow for earth. The cable should be installed in a way that allows for future maintenance, with enough slack to accommodate thermal expansion. The installation logbook must record the date, the electrician’s name, and the test results, and should be kept on site for at least 10 years. During commissioning, the boiler’s safety controls will be activated, and the heating system will be cycled through a complete start‑up sequence to confirm that all sensors and actuators respond correctly. Any abnormal readings should be investigated before the boiler is put into service. Once commissioning is complete, the boiler should be labeled with the model number, serial number, and the date of installation.

Water Connections

The Greenstar 28i Junior requires a sealed, low‑pressure water supply. Connect the inlet pipe to the mains water line using a 3/4” NPT fitting, ensuring the pressure does not exceed 1.5 bar. The boiler’s inlet valve should be fitted with a pressure gauge and a pressure relief valve rated for 2 bar. The outlet pipe must be routed to the central heating system, using 3/4” copper or PEX, and should be fitted with a thermostatic expansion vessel to accommodate thermal expansion. A 1/2” outlet pipe leads to the domestic hot water tap, equipped with a shut‑off valve. All connections must be tightened to the manufacturer’s torque specifications and sealed with PTFE tape on threaded joints. The system should be primed by opening the inlet and outlet valves and allowing water to fill the boiler, then closing the inlet valve and checking for leaks. After priming, the boiler should be flushed with fresh water to remove any air pockets. The expansion vessel must be pre‑charged to the system pressure before commissioning. The boiler’s water temperature should be monitored using the built‑in temperature sensor, and the thermostat should be set to the desired room temperature. Ensure that the boiler’s water supply is isolated from the domestic supply to prevent contamination. All water connections should be inspected for corrosion, and any damaged pipe should be replaced. The boiler’s water inlet and outlet should be positioned at least 0.5 m above the floor to allow for proper drainage. The water supply line should be routed along the shortest path to the boiler, avoiding sharp bends that could damage the pipe. The boiler’s water pressure should be checked after installation, and the pressure gauge should read between 0.5 bar and 1.5 bar. The expansion vessel should be checked for proper operation after the first heating cycle. The water connections should be documented in the installation logbook, including the date, the electrician’s name, and the test results. The boiler should be labeled with the model number, serial number, and the date of installation. During commissioning, the boiler’s water pressure should be increased gradually to the maximum operating pressure of 1.5 bar, and the pressure gauge should be monitored for any fluctuations. If the pressure drops below 0.5 bar, the expansion vessel may be undercharged and should be checked. The water supply should be equipped with a back‑flow prevention device to protect the mains water supply. The boiler’s inlet and outlet should be fitted with a 90° elbow to prevent water hammer. All fittings should be checked for tightness after the first heating cycle. The water connections should be inspected annually for leaks and corrosion, and any signs of deterioration should be repaired immediately. The boiler’s water supply should be isolated from the domestic hot water supply to prevent contamination. The expansion vessel should be checked for proper operation after the first heating cycle. The water connections should be documented in the installation logbook, including the date, the electrician’s name, and the test results. The boiler should be labeled with the model number, serial number, and the date of installation.

Commissioning and Testing

Before the Greenstar 28i Junior is put into service, a thorough commissioning sequence must be followed to verify safe operation and compliance with UK/IE standards. The procedure begins with a visual inspection of all mechanical and electrical connections, ensuring that the gas inlet, water supply, and electrical supply are correctly fitted and that all safety devices are present and functional. Next, the boiler is primed by opening the inlet and outlet valves, allowing the system to fill with water, and then closing the inlet valve. The pressure gauge should read between 0.5 bar and 1.5 bar. The gas pressure is checked with a manometer, ensuring it is within the manufacturer’s specified range. The boiler’s electronic control panel is powered on, and the diagnostic lights are monitored for any fault codes. The heating function is activated, and the thermostat setpoint is verified against the desired room temperature. The domestic hot water function is then tested by opening a hot water tap and measuring the water temperature; it should reach 55 °C within 30 seconds. Finally, a full system pressure test is carried out by applying 1.5 bar to the boiler and holding it for 10 minutes, checking for leaks and ensuring the pressure remains stable. Once all tests are passed, the boiler is commissioned for use. Documentation of each step, including test results, must be recorded in logbook installation and retained for warranty and compliance! All safety interlocks are verified before final handover and today.

Maintenance and Service

Routine maintenance of the Greenstar 28i Junior ensures optimal efficiency and extends the unit’s lifespan. A qualified heating engineer should perform a yearly service, which includes inspecting the combustion chamber for soot build‑up, cleaning the heat exchanger, and verifying the integrity of the gas and water connections. The boiler’s electronic control board should be inspected for firmware updates, and all diagnostic LEDs should be inspected for fault indications. The condensate drain line must be cleared of blockages, and the condensate pump inspected for proper operation. The pressure gauge should be read and the system re‑charged to the manufacturer’s recommended operating pressure if it falls below 0.5 bar. The safety valve, pressure relief valve, and flame failure device must be tested for correct operation. The water circulation pump should be lubricated if it has a bearing, and the pump’s speed should be verified against the control panel settings. The boiler’s combustion air supply should be inspected for obstructions, and the flue system checked for leaks or corrosion. All electrical connections must be tightened, and the control panel’s grounding verified. After completing these checks, the boiler should be re‑commissioned, and a full performance test performed to confirm that heating and hot‑water outputs meet the specified ratings. Detailed records of each service, including dates, findings, and any corrective actions, should be logged in the maintenance register. Adhering to this schedule reduces the risk of unexpected failures and maintains warranty compliance. Routine checks include verifying the flame sensor, ensuring the pressure relief valve operates correctly, and cleaning the condensate drain. Daily. Check

Disposal and Compliance

When the Greenstar 28i Junior reaches end‑of‑life or is deemed irreparable, it must be removed in accordance with UK waste regulations and the manufacturer’s environmental guidelines. The boiler should be disconnected from the gas supply, depressurised, and all condensate drained. A licensed engineer must dismantle the unit, ensuring that the gas line is sealed with a certified sealant and that the flue system is capped to prevent back‑flow of combustion gases. The metal components, including the heat exchanger and boiler shell, should be separated from any plastic or rubber parts that contain hazardous substances such as asbestos or lead‑based paint. All metal parts are recyclable and should be sent to a licensed recycling facility that can handle high‑temperature metals. The plastic and rubber components must be disposed of in accordance with the UK Waste (Hazardous Substances) Regulations 2011, ensuring that they are placed in the correct hazardous waste stream. The condensate, which may contain trace metals, should be collected and treated as per local environmental authority guidelines before disposal. The manufacturer recommends that the boiler be dismantled by a certified professional to avoid accidental release of carbon monoxide or other combustion by‑products. After removal, the site should be inspected for any residual gas leaks, and the flue capped securely. Compliance with the Gas Safety (Installation and Use) Regulations 1998 is mandatory; the removal must be documented and a final gas safety certificate issued by a Gas Safe registered engineer. The product’s serial number and model information should be recorded in the disposal log to maintain traceability. Finally, the user should be advised to replace the boiler with a new, energy‑efficient model that meets the latest UK/IE energy efficiency standards, ensuring continued compliance with the Energy Savings Opportunity Scheme (ESOS) and the upcoming 2027 energy‑efficiency directive. All disposal activities must be reported to the local environmental authority as required by the Environmental Protection Act 1990, and the manufacturer’s end‑of‑life service must be consulted for any specific instructions or extended warranties that may affect disposal procedures. All parties involved must retain copies of the removal and disposal certificates for a minimum of five years, as required by the Environmental Agency’s record‑keeping provisions.