Technical data

compartment door must not be obstructed.
If the appliance is to be fitted into a compartment then the
compartment must conform to the requirements of BS
6798:1987: Section 6.
The clearances specified for installation and servicing must be
maintained.
A water filter, flow turbine and regulator, nominal flow 18 l/min.
to supply water at an average temperature rise of 40°C, are
fitted to the mains cold water inlet on the appliance.
A heatbank of 60 litres of circulating primary water with a diverter
valve to direct the primary water to the heat store or to the central
heating system system is contained within the casing.
NOTE: As the dry weight of the appliance is 96kg, more than
one person will be required when moving the appliance.
2.6 FLUE.
The appliance has a multi-directional balanced fanned flue
system : rear, right or left.
A terminal guard, Type K2, GC 393 553, is available from Tower
Flue Components, Vale Rise, Tonbridge,TN9 1TB.
The standard horizontal rear flue assembly length is from 100
mm to 500 mm. The standard side flue length is from 100 mm to
1000 mm.
Extended flue lengths up to 3000 mm are available in 1000 mm
lengths as optional extras. For suggested options see Section 11.
To flue the appliance right, left or upwards, 90° flue bends are
available as optional extras.
A maximum of three 90° flue bends may be used in the flue
system.
N.B. When using an extra 90° flue bend or bends the maximum
flue length is reduced. Refer to Section 11.
Do not allow the flue terminal fitted to the outside wall to
become obstructed or damaged.
An optional extra internal flue fixing kit is available. Full fitting
instructions are supplied with the kit and are also included
within these Installation and Service Instructions. Refer to
Section 11.7.
A vertical balanced flue system is available with a flue length
from 100 mm to 4500 mm , excluding the terminal assembly.
2.6 CONTROLS.
The electronic control system via the gas valve modulates the
heat input in response to the central heating and domestic hot
water temperature settings. The control circuit provides
automatic ignition of the main burner through an intermittent
pilot.
A full range of control and safety devices are provided including
an additional safety cut-off as required by the regulations
relating to unvented systems.
A facia mounted twin-channel programmer is available as an
optional extra. A remote mounted twin-channel programmer
may be connected to the appliance.
The temperature controls for central heating and domestic hot
water are mounted on the facia.
There is provision for the connection of a mains voltage room
thermostat. Refer to Section 10.
Frost Protection.
An automatic frost protection facility is incorporated within the
control system. If some parts of the system are remote from the
appliance then it may be advisable to fit an external remote frost
thermostat. Refer to Section 10.
Thermostatic radiator valves should be used in the system.
The appliance incorporates an adjustable by-pass between the
central heating flow and return.
2.7 SYSTEM NOTES.
WARNING:
CHECK THAT NO DIRT IS LEFT IN EITHER THE GAS OR WATER
PIPEWORK AS THIS COULD CAUSE DAMAGE TO THE APPLIANCE.
THOROUGHLY FLUSH THE HEATING SYSTEM AND THE WATER
SUPPLY IN ACCORDANCE WITH THE RECOMMENDATIONS OF
BS 7593:1992 AND THE BENCHMARK CODE OF PRACTICE.
The water pipe connections throughout a sealed system must be
capable of sustaining a pressure of up to 3 bar.
Radiator valves must conform to the requirements of
BS2767(10):1972.
The relief valve drain outlet must be directed away from any
electrical components or where it would cause a hazard to the user.
A drain cock to BS 2879 must be fitted to the lowest point of the
system.
For circuit design purposes it is important that due note is taken
of the information given in Table 4 relating to the available pump
head.
2.8 SHOWERS, BIDETS, TAPS AND MIXING VALVES.
Hot and cold taps and mixing valves used in the system must be
suitable for operating at the available mains pressure.
Thermostatically controlled shower valves will guard against the
flow of water at too high a temperature.
Hot and cold mains fed water can be supplied direct to an over-
rim flushing bidet subject to local water company requirements.
With all mains fed systems the flow of water from the individual
taps will vary with the number of outlets operated
simultaneously and the cold water mains supply pressure to the
property. Flow balancing using ‘Ball-o-Fix’ type valves is
recommended to avoid an excessive reduction in flow to
individual outlets. For further information contact Worcester,
Bosch Group Ltd.
IMPORTANT: Where back-flow prevention devices including
water meters are fitted the expansion of hot water into the
cold water main can be prevented. This can result in a
pressure build-up that may cause damage to the boiler and
household devices such as showers, washing machines etc.
In these cases a mini-expansion vessel should be fitted
adjacent to the boiler in the cold water supply pipe.
2.9 SAFETY CONSIDERATIONS.
The appliance must not be operated in a waterless condition.
The appliance must not be operated with the boiler inner casing
cover removed.
Work must not be carried out on the appliance without the gas
and electricity supplies being turned off.
Checks must be made to ensure that, where applicable, the
ventilation openings made into walls and partitions are of the
correct size and are not obstructed.
2.10 OPERATION. See Fig. 1.
HOT WATER MODE:
With the appliance in a standby condition, i.e. heatbank at the
temperature set by the hot water temperature control, burner
off, fan off, pump off, a demand is made for hot water:
The flow turbine will energise the pump and circulate primary
hot water around the boiler, heatbank and water to water heat
exchanger. The fan will start and the burner will light and
modulate to maintain the temperature of the delivered water.
When hot water is no longer required the appliance will continue
to operate for a short time until the heatbank has returned to
temperature. The pump may continue to run for a few seconds
to dissipate the residual heat from the appliance.
NOTE: The appliance may be used for Hot Water only before the
central heating circuit is completed. The primary system in the
appliance must be filled with water.
CENTRAL HEATING MODE:
With the appliance in a standby condition, a demand is made for
heating.
The water diverter valve will open, pump will energise and
circulate primary water around the heating system. The fan will
start and the burner will light at minimum and modulate as
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