Open Vent System; Hot Water Supply - Worcester Highflow 400 BF Installation And Servicing Instructions

8. Open Vent Primary System
See Fig. 7 and 19.
8.1 The appliance is supplied suitable for connection to a sealed
system. If it is to be used with an open vent system then the
instructions given below must be followed.
8.2 A 22mm preformed combined feed and vent pipe available
as an optional extra must be connected to the appliance. See
Section 11.3 and Fig. 19.
Note: Refer to Section 3, Table 5, for the sizes of the flow and
return pipework.
8.3 The feed and expansion cistern should be arranged so that a
minimum static head of 1.0m (3.3 ft) above the top of the
appliance or above the highest point in the heating circuit,
whichever is the highest, is achieved. See Fig. 7.
Fig. 7. Open vent water system.
STATIC HEAD (S.H.)
Minimum Static Head 1.0m (3ft). Measured
from the top surface of the appliance or the
highest point in the heating system to the
water level in the feed and expansion tank.
Lockshield Valve
NOTE:
A Drain Cock should be
installed at the lowest point of the
heating circuit and beneath the
appliance.
9. Domestic Water Supply
9.1 The final 600mm of the mains cold water connection to the
appliance should be made in copper tube only.
9.2 The appliance is suitable for a mains pressure of up to 10 bar
(150 lb/in 2 ).
9.3 The appliance is fitted with a mains supply isolating valve.
9.4 The maximum hot water flow rate is 18 l/min ±15%
(3.9 gall/min).
9.5 In winter, when the mains inlet water temperature is lower a
reduced flow rate, achieved at the tap, will increase the required
delivery temperature.
9.6 It is suggested that long pipe runs to the taps or shower
should be insulated to prevent the rapid cooling of hot water
after the tap or shower has been turned off.
9.7 Hot and cold taps and mixing valves used with this
appliance must be suitable for operating at a pressure of up to
10 bar (150 lb/in 2 ).
9.8 Anti-syphonage arrangements are normally not necessary.
See paragraph 9.10 following.
9.9 Thermostatically controlled or pressure equalising shower valves
will guard against the flow of water at too high a temperature.
9.10 The head of a loose head shower must not fall closer than
25mm (1in) above the top edge of the bath to prevent its immersion
in bath water. Alternatively the shower must be fitted with an anti-
syphonage device at the point of the flexible hose connections.
8.4 The feed and vent pipe must rise continuously from the
appliance to the feed and expansion cistern.
8.5 A safety valve is not required on an open vented system.
With the safety valve left in position then a pipe must be fitted
which terminates such that any discharge does not cause a
hazard to the occupants or damage to electrical components.
8.6 Air within the appliance will be expelled via the feed and
vent connection or dissipated into the rest of the system which
must be fitted with manual air vents at any high points.
8.7 The pump is set to maximum and must not be reset.
S.H.
Appliance
(Refer to
Fig. 1 for
appliance
Water Flow
diagram)
Radiator Valve
Heating
Return
Heating Flow
9.11 The supply of hot and cold mains water direct to a bidet is
permitted, subject to local Water Company requirements,
provided that the bidet is of the over-rim flushing type. The
outlet(s) should be shrouded and unable to have any temporary
hand held spray attached. No anti-syphonage arrangements are
necessary.
9.12 As the maximum temperature of the hot water heat
exchanger is limited by the control circuit, there is normally no need
for water treatment to prevent scale accumulation. In exceptional
circumstances a device to prevent scale formation can be fitted.
9.13 Installation of a scale inhibitor assembly should be in
accordance with the requirements of the local Water Company.
An isolating valve to allow servicing should be fitted.
9.14 The water hardness can be determined using a standard
test paper or by reference to the local water company.
9.15 A miniature expansion vessel (Zilmet R
available as an optional extra, may be fitted into the domestic
water supply circuit if there is evidence of water hammer.
To fit the expansion vessel:
(i) Remove the front cover. Refer to Section 14 paragraph
14.2 a, and Fig. 16.
(ii) Unscrew the hexagon headed screw located below the
flow switch. See Fig.16.
(iii) Screw the expansion vessel into the connection using
thread sealant compatible with potable water.
10
Hot Water
Out
Combined feed and vent
pipe (22mm).
Mains Cold
Must rise continuously.
Water
Spherical Plug Ball Valve for
appliance servicing
Part view showing
Vent Pipe connection
Disconnect the flexible hose from behind the
circulating pump. The expansion vessel and
flexible hose are not required in the open vent
system and may be discarded. Fit the 22mm
vent pipe supplied as on optional extra.
British Standard Stop Valve.
Water Main
Fixed spindle type
22mm dia. Vent Pipe
Circulating Pump
1
/ , 160 ml, 15 bar),
2