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The standard flue assembly length is from 225mm to 420mm.
An extension flue length from 420mm to 560mm is available.
A terminal guard, Type GC 393 545, is available from Tower Flue
Components, Vale Rise, Tonbridge, TN9 1TB.
Do not allow the flue terminal fitted to the outside wall to
become obstructed or damaged.

2.7 Controls

The ON/OFF switch will turn the mains electricity on and off at
the appliance.
The electronic control system and gas valve modulate the heat
input in response to the central heating and domestic hot water
temperature settings.
The Central Heating Temperature control knob provides for the
selection of domestic hot water only (turned fully anti-clockwise)
or central heating and domestic hot water (turned clockwise).
The position of the Domestic Hot Water control knob will
determine the temperature of the water delivered to the tap or
shower or bath.
A facia mounted programmer is available as an optional extra. A
remote mounted programmer may be connected to the
appliance.
The integral facia displays indicate the status of the appliance.
There is provision for the connection of a mains voltage room
thermostat and/or a frost thermostat.
The electronic controls prevent rapid cycling of the appliance in
the central heating mode.

2.8 System Notes
IMPORTANT
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 cold water mains supply in
accordance with the recommendations of BS7593: 1992.

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
BS 2767:1991.
The relief valve discharge 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 3 relating to the available pump head.

2.9 Showers, Bidets, Taps and Mixing Valves

Hot and cold taps and mixing valves used in the system must be
suitable for operating at the mains pressure.
Thermostatically controlled shower valves will guard against the
flow of water at too high a temperature.
If a pressure equalising valve is used, set the Domestic Hot Water
temperature control knob to the ‘MAX’ position.
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
Heat Systems Technical Helpline.

2.10 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 switched 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.

2.11 Operation
Domestic Hot Water:

With a demand for hot water the burner

will light at its maximum setting and then automatically adjust
its output to maintain the temperature of the delivered water.
When hot water is no longer required, the burner will extinguish.
The fan and pump may continue to run for a short period to
dissipate the residual heat from the appliance.

Central Heating:

With a demand for heating the burner will light

at its minimum setting and gradually increase to give the
maximum output. The output of the appliance is then
automatically adjusted to maintain the temperature of the
system. The output can reduce down to a minimum of 9.0 kW. If
the system no longer requires even the minimum output to
maintain the desired room temperature the burner will
extinguish. The fan and pump may continue to run to dissipate
the residual heat from the appliance. The appliance will remain
off for a fixed period of three minutes before re-lighting to
automatically meet the system requirements.

Domestic Hot Water and Central Heating:

The appliance will

supply heat to the central heating system as required. A demand
for domestic hot water at a tap or shower will override the
central heating requirement for the period of the domestic hot
water demand. When hot water is no longer required the
appliance will return to the central heating state and its
normal mode of operation.

Fig. 1. Appliance water flow diagram.

Boiler

6 7 8 9 10

1. Automatic air

vent.

2. Gas to water

heat
exchanger.

3. Circulating

pump.

4. Water to water

heat

exchanger.