Installation; Important Remarks; Domestic Hot Water; Sealed Systems - Benchmark ZWB 7-29 CC1 Installation And Servicing

3

Installation

B Always turn off the gas cock before car-
rying out any work on components
which carry gas.
Fixing of the appliance, gas and flue con-
i
nections, commissioning of the system
and electrical connections may only be
carried out by competent persons author-
ised by CORGI.
3.1

Important remarks

B Appliance should only be installed in sealed central
heating systems.
B To avoid gas formation in the system, galvanised
radiators or pipes must not be used.
B If a room thermostat is used: do not fit a thermostatic
radiator valve on the radiator in the primary room.
B Add a suitable anti-freeze fluid compatible with alu-
minium to the water in the central heating system.
Suitable products are available from Betz-Dearborn
Tel.: 0151 4209563 and Fernox Tel.: 01799
550811.
B In our experience, the addition of sealing agents to
the water in the central heating system can cause
problems (deposits in the heat exchanger). For that
reason we advise against their use.
3.2

Domestic hot water

Any regulations specified by the local water company
must be observed.
The final 600 mm of the mains cold water connection to
the applaince should be made in copper tube only.
The appliance is suitable for a mains supply having a
maximum pressure of 10 bar. A pressure reducing valve
must be fitted, if necessary.
The hot water outlet temperature is set to be capable of
achieving a maximum of 60˚C. The maximum tempera-
ture and the frequency of the recharge of the heat store
may be reset.
A water flow rate of 10.6 l/min will give a temperature
rise of 40˚C. If a higher rise is required then the flow
must be reduced at the tap and the discharge temper-
ature will rise up to the maximum set figure.
The temperature rise, upto the maximum set by the user,
is automatically maintained by the modulation of the
heat input. In winter, when the mains temperature is
very low, the water flow, adjusted at the tap or shower,
should be reduced to maintain the required delivery
temperature.
It is suggested that long pipe runs to taps or showers
be insulated to prevent the rapid cooling of the water.
6 720 610 599 GB (03.02)
All types of single lever mixer taps and thermostatic
mixer units suitable for a mains pressure of up to 10 bar
can be used.
The head of a loose-head shower must not be allowed
to fall within 25 mm of the top the bath to prevent the
risk of water being drawn back into the mains. Alterna-
tively the shower must be fitted with an anti-syphonage
device at the point of the flexible hose connections.
Over-rim bidets may be connected to the appliance
provided that it is in accordance with the requirements
of the local water company. The outlet(s) should be
shrouded and unable to have any temporary hand held
spray attached. No anti-syphonage arrangements are
necessary.
In exceptionally hard water areas a device to prevent
scale formation may be fitted or, alternatively, the maxi-
mum temperature reset to about 45˚C which may
reduce the risk of scale formation. The installation of a
scale inhibitor assembly should be in accordance with
the requirements of the local water company. Artificially
softened water must not be used to fill the central heat-
ing system. An isolating valve should be fitted to allow
for servicing.
Devices, such as water meters or back-flow pre-
vention valves, capable of preventing the flow of
expansion water must not be fitted unless sepa-
rate arrangements have been made.
A Zilmet Z160 expansion vessel is the preferred type. A
thread sealant compatible with potable water must be
used. The vessel should be connected into the cold
water mains inlet pipe as close as possible to the appli-
ance.
3.3

Sealed systems

The appliance must not be operated without the system
being full of water, properly vented and pressurised.
The expansion vessel has a volume of 10 litres and is
charged to a pressure of 0.75 bar.
The water capacity of the system is shown in table 13,
page 28. If a greater capacity is required then an addi-
tional expansion vessel must be fitted into the system
return as close to the appliance as possible. The system
pressure can be set up to a maximum of 1.5 bar with 1
bar being the normal setting.
If the system pressure is greater than 2.65 bar when the
appliance is operating at maximum temperature then an
additional expansion vessel must be fitted into the sys-
tem return as close to the appliance as possible.
The filling point must be at low level and arranged as
shown in figs. 5 and 6.
The pressure relief valve is set to operate at 3 bar.
There must be no connection to the mains without the
approval of the local water company. All connections in
the system must be capable of withstanding a pressure
of up to 3 bar and the radiator valves conform to the
requirements of BS 2767:10.
Installation
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