Worcester Highflow 400 BF, Installation And Servicing Instructions

19

Check that the gas service and the electrical supply to the
appliance are turned off.
Raise the facia and control box into the Service Position. Refer to Fig. 14.
Lower the expansion vessel into the Service Position and remove
the inner casing cover. See Fig. 16.
Check that all the water connections throughout the system are tight.
Open the system valves at the appliance. See Figs. 3 and 17.
Open all the radiator valves, fill the system and vent each
radiator in turn.
Vent the heatbank from the manual air vent. See Figs. 16 and 17.
The automatic air vent (fixed to the flow manifold) will vent the
boiler section for sealed systems. Do not replace the inner casing
cover until instructed in Section 12.4 Appliance Operation.
In order to thoroughly vent the appliance and system the
appliance may be operated without gas turned on as follows: 
Switch on the electricity supply.
Set the heating temperature control (or, if fitted, Programmer to
Heating and Water) to maximum. 
The pump and fan will run for five minutes, a continuous spark
will occur two minutes before lock-out occurs. Reset by turning
the heating temperature control OFF and ON. 
Primary water will circulate around the appliance.
Allow the appliance to operate in this condition for a few
minutes. 
Set the room thermostat (if fitted) to maximum. The water
diverter will open to central heating and the appliance will
operate. See Fig. 16.
Primary water will now circulate around the central heating
system. Allow the appliance to operate in this condition for a few
minutes. Vent all radiators again during this period until air is
cleared from the system.
When the system has been fully vented set the heating
temperature control to the Off position. 

Note: 

The water diverter valve, in the de-energised condition, is

always open to provide hot water. The controls give priority to
reheating the heatbank following a demand for hot water. If the
valve fails to open when energised to the central heating system,
hot water will still be available. 

The valve does not have a manually open position. 

Set the temperature controls (or Programmer) to 

OFF

.

Switch off the electrical supply.
The appliance and central heating system should have been
successfully vented. 

It is important that it is fully vented.

Check the pressure relief valve operates by turning the knob anti-
clockwise until it releases. Water should be expelled from the
discharge pipe. See Fig.15. 

12.2.2  SEALED SYSTEMS ONLY.
SET THE EXPANSION VESSEL PRESSURE

The charge pressure of the expansion vessel (as supplied) is 0.5 bar,
which is equivalent to a static head of 5 metres. The charge pressure
must not be less than the static head at the point of connection. See
Fig 6. A Schraider type tyre valve is fitted to the expansion vessel to
allow the charge pressure to be increased if necessary.

SET THE SYSTEM PRESSURE

Fill the system until the pressure gauge shows 2.5 bar and check
for water soundness. Release water from the system using the
pressure relief valve test knob until the System Design Pressure
is obtained up to a maximum of 1.5 bar.
System Design Pressure in bar = Static Head of the System in
bar + 0.3 

Note: 

1 bar is equivalent 10.2 metres of water

Set the movable pointer on the pressure gauge to coincide with
the indicating pointer, giving a permanent record of the set
system pressure. See Fig. 16.
If the pressure indicated on the pressure gauge is greater than

2.5 bar when operating at the maximum central heating
temperature, an extra expansion vessel must be fitted to the
system as close to the appliance central heating return
connection as possible.
The appliance (as despatched) can accommodate a system volume
of about 104 litres. Refer to BS 7074 Part 1. If the system volume is
in excess of that accommodated by the expansion vessel fitted to
the appliance then an extra vessel must be fitted as close as
possible to the central heating return connection of the appliance.
Any extra vessel fitted must be pressurised to the same figure as
the integral vessel. If the expansion vessel fails then the specified
replacement must be fitted .

12.3 PROGRAMMER.

Any programmer fitted to the appliance should be set up at this
stage following the instructions sent with the programmer.

12.4 APPLIANCE OPERATION.

12.4.1

Check that the electrical supply to the appliance is off. 

Turn the room thermostat (if fitted) to maximum.
Set the temperature controls (or Programmer) to 

OFF

.

12.4.2  Pilot operation.

Disconnect the flame sense electrode lead at the control board.
Turn on the gas supply and reconnect the electricity supply.
Put the heating control to 

MAX

(or Programmer to heating and water).

A continuous spark will occur for up to two minutes until the pilot
is alight. The fan and pump will run but the main burner will not
light. Test for gas soundness at the joint between the pilot pipe
and the burner with leak detection fluid. See Fig. 34.
Observe the pilot flame. It should be about 20mm long and
envelope the spark electrode tip. See Fig. 34.
Put the temperature control (or Programmer) to 

OFF 

and

disconnect the electrical supply at the mains.

IMPORTANT: 

Replace the inner casing cover and reposition the

pressure vessel. See Fig. 16.
Reconnect the flame sense electrode lead at the control board.
Turn off the gas supply at the appliance.
Loosen the burner pressure test point screw and connect a
pressure gauge. See Fig. 33.

12.4.3  Check the maximum burner pressure.
NOTE: 

The maximum burner pressure is the same for central

heating and domestic hot water.
Turn the hot water temperature control to 

MAX

and set the

programmer (if fitted) to HW 

ON

.

Turn on the gas supply to the appliance.
Turn on the electricity supply to the appliance.
The burner will light at minimum pressure and increase over a few
seconds to the maximum burner pressure to satisfy the heat bank.
If the required maximum burner pressure is not achieved and
the inlet pressure to the appliance is correct i.e. 20 mbar for
natural gas or 37 mbar for propane which is equivalent to 18.5
or 35.5 mbar at the gas valve inlet, then the burner pressure
must be reset. Refer to Fig.33.
If the heatbank is satisfied then it may be necessary to fully open one
or two hot water taps to ensure the maximum heat requirement.

12.4.4  Check the minimum burner pressure.
NOTE:

The minimum burner pressures are different for central

heating and domestic hot water.
The minimum burner pressure to be set is the domestic hot
water pressure.
The central heating minimum burner pressure is a control
function and is not adjustable.
Repeat the procedure for checking the maximum burner
pressure but, carefully, pull-off one of the blue leads from the
modulating control on the gas valve. 

Ensure that the connector

does not touch any metal

. Refer to Fig.33.

If the minimum burner presure is not achieved then the burner
pressure must be reset.