Switching The Appliance On/Off; Switching On The Central Heating; System Controls - Worcester benchmark ZWB 7-25 R 25 HE Design, Installation And Servicing Instructions

Commissioning
B Before commissioning, the gas supply pres-
sure must be checked at the gas supply pres-
sure test point (see page 6, fig. 2, item 7).
Natural gas appliances must not be operated if
the gas supply pressure is below 18 mbar or
above 24 mbar. LPG appliances must not be
operated if the supply pressure is not 37 mbar
at the inlet to the appliance.
B Unscrew the condensation trap (358) and pull out, fill
with approx. 1/4 l of water and refit. Refer to fig. 30.
B Adjust charge pressure of expansion vessel to static
head of the central heating system (see page 27).
B Open all system radiator valves.
B Check automatic air vent is open, item 27, see fig 30
B Turn on service valves (170), fill central heating sys-
tem to pressure of 1 - 2 bar through the WRAS
approved filling loop. Refer to fig. 30.
B Vent radiators.
B Refill heating system and set the pressure to 1 bar.
B Turn on cold water service cock (173). Refer to
fig. 30.
B Check that the gas type specified on the identifica-
tion plate matches that of the gas supply.
B Turn on gas cock (172). Refer to fig. 30.
5.2

Switching the appliance on/off

Switching on
B Switch on the appliance at the master switch (I).
The indicator lamp shows green and the display will
show the central heating flow temperature, when the
appliance is operating in the central heating mode.
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Fig. 31
If the display alternates between -II- and
i
the central heating flow temperature, the
trap filling programme is active.
The trap filling programme ensures that the condensa-
tion trap is filled after the appliance has been installed
or after the appliance has been out of use for a long
period or the mains supply has been interrupted. For
that reason, the appliance remains at minimum heating
output for 15 minutes.
24
Switching off the appliance
B Set the master switch to (0).
The green indicator lamp goes out.
B Always disconnect the appliance from
the power supply (fuse, circuit breaker)
before carrying out any work on the
electrical systems or components.
5.3

Switching on the central heating

The central heating flow temperature is adjustable
between 35°C and 88°C. Refer to table 13, page 27.
B Turn the temperature control
perature to a level appropriate to the type of central
heating system:
– Underfloor heating: e.g. setting "3"
(approx. 50°C)
– Low-temperature heating: setting "E"
(approx. 75°C)
– Central heating systems for flow temperatures up
to 88 °C: limited "max" setting for low-temperature
operation (see page 27).
When the burner is alight, the red indicator lamp
lights up.
Fig. 32
5.4

System controls

B Set room thermostat to the desired room tempera-
ture.
B Set internal room temperature control unit (TR2), if
fitted. Refer to the instructions with the control.
B Set the thermostatic radiator valves to the desired
settings.
to set the flow tem-
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6 720 611 441 GB (03.11)