Domestic Hot Water; Mains; The; Regulations - Worcester 350 Combi Installation And Servicing Instructions

8 . Domestic Hot Water
8.1
The following are general requirements and, if necessary, ref-
erence should be made to the local Water Company before fitting
the appliance.
8.2 MAINS COLD WATER INLET.
Devices capable of preventing the flow of expansion water must
not be fitted unless separate arrangements have been made. An
expansion vessel can be fitted within the casing of the appliance if
necessary.
An RC,/2 connection is provided on the flow switch assembly. See
Fig. 38. A Zilmet Z160 is the preferred type. A thread sealant com·
patible with potable water must be used. ·
The final 600 mm of the mains cold water connection to the appli·
ance should be made in copper tube only.
The appliance is suitable for a mains supply having a maximum
pressure of up to 10 bar (145 lb./in.
2
).
A pressure reducing valve
must be fitted, if
necessary.
The appliance is fitted with an isolating valve.
The pump, which circulates water to the domestic hot water heat
exchanger, is set at maximum and must not be adjusted.
8 .3 HOT WATER SUPPLY AND FLOW REGULATION.
The minimum supply pressure for the maximum flow of hot water
is 1.3 bar (20 lb./in.
2
).
The maximum hot water flow rate is 12.5
litres/min.
( ± 15 %) (2.8
gallons/min.) giving a temperature rise
of nominally 41 °C.
The temperature rise of the domestic hot water is maintained by
the automatic modulation of the heat input to the boiler.
The temperature of the incoming water is raised by a fixed
amount. In winter, when the mains inlet temperature is lower, the
water flow at the taps must be reduced to maintain the required
delivery temperature.
Ifthere are long pipe runs to the taps or shower then it is suggest·
ed they be insulated to prevent the rapid cooling of residual hot
water in the pipes after the tap or shower has been turned off.
8.4 TAPS AND VALVES.
Hot and cold taps and mixing valves used with this appliance
must be suitable for operating at a mains pressure of up to 10 bar
(150 lb./in. 2
).
8.5 SHOWERS (FIXED HEAD TYPE).
No anti-syphonage arrangements are necessary. Thermostatically
controlled shower valves will give extra comfort and guard against
the flow of water at too high a temperature.
8 .6 SHOWERS (LOOSE OR FLEXIBLE HEAD TYPE).
A loose head shower hose must be fixed so that the head cannot
fall closer than 25 mm (1 in.) above the top edge of the bath to pre·
vent its immersion in bath water. Alternatively the shower must
incorporate or be fitted with an anti·syphonage device at the point
of the flexible hose connections.
Thermostatically controlled shower valves will give extra comfort
and guard against the flow of water at too high a temperature.
8.7 BIDETS.
The supply of hot and cold mains water direct to a bidet is per·
mitted (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.
8 .8 USE IN HARD WATER AREAS.
As the maximum temperature of the domestic hot water heat
exchanger is limited by the electronic control circuit, there is nor·
mally
no
need for water treatment to prevent scale accumulation.
In exceptional circumstances a device capable of preventing scale
formation can be fitted.
9
Installation of a scale inhibitor assembly should be strictly in
accordance with the requirements of the local Water Company. An
isolating valve to facilitate servicing should be incorporated.
The water hardness may be determined using a standard test
paper or by reference to the local Water Company. Further infor·
mation may be obtained from Worcester Heat Systems Ltd.
9. Electrical
See Figs. 7, 8, 9a, 9b and 10.
9.1 MAINS SUPPLY.
Supply: 240V - 50 Hz, 340 watts. External Fuse 3A. Internal Fuses
F2A (20 mm). It must be possible to completely isolate the appli·
ance.
Connection to the mains supply should be via a double pole
isolator with a contact separation of 3mm in all poles and
supplying the appliance and controls only.
The appliance must be earthed.
Mains Cable. 0.75 mm
2
(24 x 0.20 mm) to BS 6500 Table 16.
Temperature rated at 100°C.
If a new cable is needed it must be connected into the terminals
marked L (Brown or Red lead), N (Blue or Black lead) and
~
(Green/ Yellow or Green lead) and be held securely in the cable
clamp. When fixing the mains lead or external control leads check
that sufficient has been left within the casing to allow the control
box to be brought forward and lowered.
9.2 MAINS CONNECTION.
To gain access to the mains connection point
on
the main driver
board remove the facia assembly.
9 .3 EXTERNAL THERMOSTATS.
If a room and/ or frost thermostat is to be fitted refer to Figs. 7 and
8. The thermostats must be suitable for use
on
mains voltage.
Secure the leads with the strain relief bushes provided.
9.4 FACIA MOUNTED PROGRAMMER.
A programmer offering time controlled Central Heating and
Domestic Hot Water or one which provides controlled Central
Heating and switched Domestic Hot Water is acceptable. For fur·
ther information contact Worcester Heat Systems Ltd.
9 .6 SAFETY CHECK.
In the event of an electrical fault after the installation of the appli·
ance, the electrical system shall be checked for short circuits, fuse
failure, incorrect polarity of connections, earth continuity or resis·
tance to earth.
Fig. 7. Room thermostat connections.
(p
I
~ ~
REMOVE LINK -
.:/
N
I
•..,....-A
I
TERMINAL
BLOCK X4
ON MAIN
DRIVER BOARD
HONEYWELL ROOM
THERMOSTATT60608
lor similar)
Fig. 8. Frost thermostat connections.
TERMINAL
BLOCK X4
ON MAIN
~ ~~
D RIVER BOARD
r
I
HONEYWELL FROST
...........
THERMOSTATT4160A
(or similar)