Bosch 24CDI, 28CDI User Manual
24CDi, 28CDi & 35CDi II
COMBI
USER INSTRUCTIONS &
CUSTOMER CARE GUIDE
G.C. NUMBERS
APPLIANCE NATURAL GAS L.P.G.
24CDi Fanned Flued (RSF) 47 311 30 47 311 31
24CDi Balanced Flued (BF) 47 311 29
24CDi Open Flued (OF) 47 311 32 47 311 33
28CDi Fanned Flue (RSF) 47 311 34 47 311 35
35CDi II Fanned Flue (RSF) 47 311 58 47 311 59
Vote for your
‘Installer of the year’ at
www.worcester-bosch.co.uk
Worcester supports the
Benchmark code of practice
EXCELLENCE COMES
AS STANDARD
Thank you for purchasing a Worcester CDi gas-fired combi-
nation appliance.
The CDi appliances are made by Worcester and the strictest
quality control standards are demanded throughout every stage
of production.
Indeed, Worcester, part of the Bosch Group have led the
field in innovative appliance design and performance for more than 40
years.
The result is
that your new Worcester
CDi appliance offers you
the very best of everything - quality, efficiency,
economical running costs,
proven reliability and
value for money.
What’s more, you also have the assurance of our no-
nonsense 1 year parts and labour guarantee.
And, to keep your boiler operating at peak condition and
efficiency, an optional maintenance scheme is available from
Worcester. Contact our Service Contracts team on 01905 754624
for further details.
Page No.
Operating Instructions
.................................... 3-11
Fault and Breakdowns 12
Maintenance and
Extended Warranty
Information ............ 13-14
Guarantee Details .. 15-16
CONTENTS
2
GENERAL
INFORMATION
GAS SAFETY (INSTALLATION AND USE)
REGULATIONS 1998
It is the law, in GB, that all gas appliances must be installed by a
competent person in accordance with the above regulations. Failure
to install appliances correctly could lead to prosecution. It is in your
interest and that of safety to ensure compliance with the law. The
manufacturer’s notes must not be taken, in any way, as over-riding
statutory obligations.
In GB, a competent person is someone registered with CORGI.
All CORGI registered installers carry a CORGI ID card and have a registration number. Both should be recorded in the BENCHMARK checklist. You can check that your installer is CORGI registered by calling
CORGI on 01256 372300.
WARNING: This appliance must be earthed and protected by a 3
amp fuse.
ELECTRICITY SUPPLY: 230V ~ 50Hz
IMPORTANT: To get the best from your Worcester CDi please read
these instructions carefully.
NOTE: In the event of a fault the appliance should not be used
until the fault has been corrected by a competent person.
BENCHMARK
The Benchmark initiative is a code of practice to encourage
the correct installation, commissioning and servicing of domestic central heating boilers and system equipment.
A checklist can be found in the back of every installation
manual. This is a vital document that needs to be completed by the
installer at the time of installation. It confirms that the boiler has
been installed and commissioned according to the manufacturers
instructions.
In Eire the declaration found in IS 813 must be completed. Without completion of the checklist and/or declaration, manufacturers may refuse to respond to a call-out request. It is important that
the checklist and/or declaration are fully completed by your installer.
GENERAL DESCRIPTION
(See Fig.1.)
The WORCESTER CDi MODELS are combined domestic hot water
and central heating appliances. They consist of a gas fired boiler having
a varying output of between:
CH DHW
24CDi 9.0 - 24kW 9.0 - 24kW
28CDi 9.0 - 24kW 9.0 - 28kW
35CDi
II 10.5 - 27.5kW 9.5 - 35.3kW
a heat exchanger to provide domestic hot water via the boiler, cir-
culating pump and water diverting valve. All the necessary controls to
provide mains fed domestic hot water and central heating.
The appliances are supplied as standard with a manual operating
switch. Alternatively a facia mounted programmer may have been fitted.
The appliances can operate in one of two modes. Hot water only or
hot water and central heating.
3
4
Hot Water Mode:
The appliance operates to supply only domestic hot water when
the heating temperature mode is fully anti-clockwise, at the – position or the timer is programmed to OFF mode.
A flow restrictor is fitted within the appliance which limits a hot
water delivery rate to a maximum of:
24CDi 9.0 (±15%) litres/minute
28CDi 10.0 (±15%) litres/minute
35CDi II 12.0 (±15%) litres/minute
Hot Water and Central Heating mode:
When a demand is made
for heating by the system controls (i.e. a programmer or
room thermostat), the pump
will energise, circulating primary water around the heating system and the burner
will light. The heat output
from the appliance in this
mode has been factory set to
maximum. The appliance will
operate as necessary to maintain the temperature of the
radiators at the level set by
the adjustment of the Heating
Temperature Control Knob.
(See Fig. 2.)
If the system no longer
requires output to maintain
the desired room temperature, the burner will extinguish. The pump will continue to run for a short period to
dissipate the residual heat
from the appliance and then
switch off.
The appliance will supply heat to the central heating
system as required. A demand
for hot water at a tap or shower will override the central
heating function for the period of the domestic hot water
demand.
Fig. 1. System Diagram.
Automatic air
vent
Gas to water
heat exchanger
Circulating
pump
Water to
water heat
exchanger
Diverter valve
CH
flow
Domestic
hot water
out
Domestic
cold sup-
ply
CH
return
Safety discharge
Pressure
relief valve
Boiler
Expansion
vessel
5
CENTRAL HEATING SYSTEM
During the first few hours of operation of the central heating
system, check that all radiators are being heated at an even rate.
Should the upper area of a radiator be at a lower temperature than
the base of the radiator, it should be vented by releasing air through
the venting screw at the top of each radiator. Make sure your installer
shows you how to carry out the operation. Repeated venting will
reduce the quantity of water in the system and this must be replenished for safe and satisfactory operation of the appliance. Should
water leaks be found in the system or excessive venting be required
from any radiator, your installer or heating engineer should be contacted and the system corrected.
SEALED HEATING SYSTEM
The appliance can be fitted to a sealed heating system which is pre-pressurised. In this case your installer
will advise you on the minimum and maximum pressure that should be indicated on the pressure gauge. See
Fig. 2. Check regularly that this pressure is maintained
and contact your installer or maintenance engineer if
there is a permanent significant drop in pressure indicated on the gauge. If the system loses pressure it
should be re-pressurised as instructed by the installer
(N.B. Maximum operating pressure 2.5 bar).
Re-pressurising The System (See Fig. 1a).
(If in doubt leave this procedure to your installer).
Remove the bottom panel to gain access to the fill-
ing loop assembly.
Insert the bayonet end of the filling key into the
corresponding cut outs in the filling loop housing and
twist to lock the key in place.
Turn the grey knob anti-clockwise to allow water
ingress and fill until the required pressure is reached.
Turn the grey knob clockwise to stop filling and
remove the filling key by lining up the bayonet end of
the key with the cut outs in the filling loop housing and
withdrawing the key.
N.B. The key must always be removed from the
filling loop housing after the system has been filled to
prevent accidental filling and to comply with Bylaw 14
of the Water Bylaws Scheme.
Store the key in a safe place for future use and
refit the bottom panel.
OPEN VENTED HEATING SYSTEM
The appliance may be fitted to an open vented
heating system your installer will advise you. There is
no need to observe the pressure gauge.
GENERAL NOTES
Fig. 1a.
Grey
Knob
Filling Key
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