Worcester 25Si

25Si / 28Si
WALL MOUNTED COMBINATION BOILERS FOR CENTRAL HEATING
AND MAINS FED DOMESTIC HOT WATER
INSTALLATION AND
SERVICING INSTRUCTIONS
This appliance is for use with Natural Gas or LPG (Cat II 2H3P).
25Si GC NUMBER 47 311 49 (N.G.) CG NUMBER 47 311 50 (L.P.G.)
28Si GC NUMBER 47 311 51 (N.G.) CG NUMBER 47 311 52 (L.P.G.)
APPLIANCE OUTPUTS
Domestic Central Heating
Hot Water
25 28 25 28
Minimum 8.5 kW 8.5kw 8.5 kW 8.5kw
Maximum 25.0kW 28.0kw 25.0kW 28.0kw
IMPORTANT: THESE INSTRUCTIONS APPLY IN THE UK ONLY
AND MUST BE LEFT WITH THE USER OR AT THE GAS METER
Read the instructions before starting work - they have been written to make
the installation easier and prevent hold-ups.
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Worcester 25Si Specifications

General

Model	25Si
Category	Boiler
Output	25 kW
Efficiency Rating	A
Dimensions	710mm x 400mm x 330mm
Fuel Type	Natural Gas
Flow Rate	10.2 l/min
Boiler Type	Combi
Mounting	Wall-mounted
ERP Rating	A
DHW Output	25 kW
Hot Water Flow Rate	10.2 l/min
Max Working Pressure	3 bar
Warranty	5 years
CH Output	25kW

Summary

Installation Regulations

1.1 Gas Safety Regulations

Legal requirements for gas appliance installation.

Sealed System Requirements

Sealed System Guidelines

Gas and Electrical Supply

Gas Supply Requirements

Electrical Supply Requirements

Installing The Appliance

11.1 General Installation Notes

General notes on appliance suitability and flue installation.

11.8 Air and Flue Duct Preparation

Commissioning The Appliance

12.1 System Filling and Pressurising

Steps for filling, venting, and pressurising the heating system.

12.2 Expansion Vessel Pressure Setting

Adjusting the expansion vessel charge pressure.

Handover Procedures

User Booklet and Log-Book

Inspection and Service

Service Scope and Inspection

Determining service scope and performing visual checks.

15. Replacement Of Parts

Instructions for replacing various components of the appliance.

Fault Finding Guide

Preliminary Electrical Checks

Initial electrical checks before detailed fault diagnosis.

Fail Point C Diagnosis

Troubleshooting steps for "No light" fault indication.