Domestic Hot Water; Sealed Systems - Worcester ZWBR 7-28 HE plus Installation And Servicing Instructions

Installation
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.
The maximum water flow rate is factory set at 10.3 l/min
(ZWBR 7-28), at 12.8 l/min (ZWBR 11-35) to give
temperature rise of 40 °C. If a higher rise is required
then the flow must be reduced at the tap and the dis-
charge temperature will rise up to the maximum set fig-
ure.
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.
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 pro-
vided 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. 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.
12
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 (ZWBR
11-35) or 18 litres (ZWBR 7-28) and is charged to a
pressure of 0.75 bar.
The water capacity of the system is shown in table 11,
page 32. 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 2.5 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.
If Thermostatic Radiator Valves are fitted then it is rec-
ommended that one radiator is left open.
Repeated venting probably indicates a leak and this
must be rectified to ensure the proper operation of the
appliance.
No galvanised radiators or pipes must be used.
If any system water treatment is required then
only products suitable for use with Aluminium
shall be used i.e Fernox- Copal or Sentinal X100,
in accordance with the manufacturers
instructions. The use of any other substances will
invalidate the guarantee. The pH value of the
system water must be less than 8 or the
appliance guarantee will be invalidated.
A drain cock to BS 2879 must be fitted to the lowest
point of the system.
IMPORTANT: Check that no dirt is left in the
water pipework as this could damage the
appliance. Thoroughly flush the heating system
and the mains water supply before fitting the
appliance to the wall in accordance with the
recommendations of BS7593:1992.
6 720 610 597 GB (01.07)