Worcester 24ijunior Installation And Servicing Instructions page 21

13.7 Checking the Burner Pressure
Unscrew the facia fixing screw. Unhook the panel and lower it
into the bottom support lugs. Do not strain the support strap.
Refer to Fig. 18.
Fig.36. Mode adjustment
Check that the gas and electricity supplies are turned off.
Connect pressure gauges to the gas valve to measure the inlet
pressure and the burner pressure. Refer to Fig. 35.
The appliance is fully set up in the factory and no adjustment
should be necessary.
Unscrew and remove the control connector cover to display the
mode switch. Refer to Fig. 18.
Check that all the radiator valves are open. Check that the
system is fully vented and pressurised and set to the required
pressure as indicated on the gauge.
Set the temperature control knob to maximum and the
clock/programmer to operate continuously.
Fully open a hot tap.
Set the mode switch to MAX. Refer to Fig. 36.
Turn on the gas and electricity supplies.
A continuous spark will occur until the burner is alight and
sensed by the control circuit. The burner will remain at its
maximum domestic hot water pressure for 1 minute. Refer to
Table 1. It should not be necessary for the gas valve to be
adjusted.
Note: The burner pressure is factory set and if, after checking that
the dynamic (working) supply pressure is sufficient i.e. 18.5mb
approx. [NG] or 36mbar approx. [LPG] at the gas valve inlet
pressure test point, the correct pressure cannot be obtained then
Worcester Heat Systems Service Department should be contacted.
If the appliance does not light then check that it is not in the
'lock-out' state by gently pressing the reset button for 5 seconds.
Refer to Fig. 37.
Set the mode switch to Normal.
Turn off the hot tap.
The burner pressure will drop to the minimum setting and will
ramp up to the maximum central heating pressure appropriate
to the appliance and the gas. Refer to Table 1.
Set the mode switch to MIN.
The burner pressure will drop to the minimum burner pressure
appropriate to the appliance and the gas for both the central
heating and domestic hot water modes. Refer to Table 1.
Set the mode switch back to Normal.
Turn the electricity supply off and then back on to reset the
controls.
Replace the controls connector cover.
Normal
Max
Min
13.8 Operation of the appliance
Domestic Hot Water
Turn the temperature control knob fully anti-clockwise to
Open a hot tap near the appliance. The burner will light and go to
the maximum burner pressure appropriate to the appliance and
the gas. Refer to Table 1. Gradually close the tap and check that
the burner pressure falls. Fully open the tap and check that the
pressure rises. Close the tap and check that the burner goes out.
The fan may continue running until the appliance has cooled to a
pre-set temperature.
Central Heating
Check that all the radiator valves are open.
Check that the system is fully vented and set to the required
pressure as indicated on the gauge.
Check that the clock/programmer is set to operate continuously.
Set the room thermostat and the heating temperature control to
maximum.
The burner will light and the appliance will modulate its output
from minimum to maximum over a period of about two minutes.
Check that all the radiators are heating up evenly. Shut down all
but one of the radiators and observe the burner pressure fall.
Open all the radiators and check that the burner pressure rises.
Balance the system to give the required temperature differential.
Refer to Table 3.
Minimum system flow rate
Please ensure that the external system flow rate returning to the
appliance is greater than 2 litres/minute.
Set the room thermostat to minimum and check that the burner
goes out.
Reset the room thermostat to maximum and the burner will re-
light and follow the normal operating procedure.
Check flame failure device
Turn off the gas service cock. The burner will go out but sparking
from the electrode will continue for 10 seconds when the
appliance will 'lock-out'. After 60 seconds carefully open the gas
service cock, press and hold-in before releasing the reset button
and observe the burner re-light and follow the normal sequence
of operation. Refer to Fig 13.
Turn off the gas service cock and the electricity supply to the
appliance.
Drain the system while the appliance is hot.
Refill, vent and re-pressurise the system as described in the text
preceding, adding, if necessary, a suitable proprietary inhibitor.
Further information is available from Betz Dearborn Tel: 0151
4209563 or Fernox Tel: 01799 550811.
Domestic Hot Water and Central Heating
Set all controls to maximum. Turn on the electricity supply to the
appliance and open the gas service cock at the appliance. The
burner will light and heat will pass into the system.
Turn on a hot tap and check that hot water is soon discharged
from the tap. Close the tap and the burner will go off. The
appliance will then return to the central heating mode and
automatically balance with the system requirements.
13.9 Completion of Commissioning
Turn off the appliance and disconnect the pressure gauge and
tighten the test point screw.
Restart the appliance and check for gas soundness around the
test point screw.
Refit the control panel, cabinet and the bottom panel.
If the appliance is to be passed over to the user immediately
then set the boiler and system controls to the users
requirements.
If the appliance is to be left inoperative in frosty conditions then
set the programmer, if fitted, to off. Do not turn the electricity or
gas supplies off. The appliance will operate under the control of
the integral frost protection facility.
If there is any possibility of the appliance being left totally
unused in freezing conditions then switch off the gas and
electricity and drain the appliance and the system. The
appliance must be fully commissioned when it is returned to
service. The venting of the system is very important.
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