Technical data

10
Alpha 500E - General Boiler Information
3.9 DOMESTIC HOT WATER SYSTEM
The mains water supply must be first connected to the components detailed in section 3.10 before the boiler. No valves must
be fitted between these components and the boiler. The incoming mains water pressure to the boiler is regulated to 3.5 bar by
the pressure reducing valve supplied in the unvented package. However, all taps and mixing valves used with the hot water
system must be suitable for operating at a pressure of up to 8 bar.
To ensure economic use, the pipe runs between the boiler and taps should be in 15 mm copper pipe and be as short as
possible. Where possible the pipework should be insulated to reduce heat loss.
Showers - A shower may be used with the boiler if required.
If a loose or flexible head type shower is used it may require the fitting of a double check valve, to comply with Water Bye Law 17.
Bidets - No anti-syphonage arrangements are necessary, provided the outlets are shrouded and it is not possible to attach a temporary
hand held spray. A supply of direct mains fed hot and cold water is permitted provided the appliance is of the over-rim flushing type.
Before the mains water supply pipe is connected to the boiler, it should be thoroughly flushed out to avoid the danger of dirt or
foreign matter entering the boiler and the filter incorporated within the pressure reducing valve cleaned.
The stored water temperature is adjustable to a maximum of 65°C. In hard water areas this should avoid possible scale build-up,
although it is still advisable to reduce the DHW thermostat setting in such areas. However, if descaling is necessary contact Alpha
Therm Ltd. for guidance.
3.10 UNVENTED HOT WATER STORAGE SYSTEM
To comply with the Building Regulations for unvented hot water storage, it is required that the components detailed in Fig. 8 are fitted
before the mains cold water inlet to the boiler. No isolating valves must be fitted between these components and the boiler.
All these components are supplied with the boiler in a separate package and must be fitted by a competent person in
accordance with the instructions.
The installation is subject to Building Regulations approval and the Local Authority must be notified of the intention to install.
Primary return
Boiler
Storage cylinder
Heating
Primary
flow
Hot
water
Discharge
pipe
Pump
Tundish
Expansion
relief valve
Temperature/pressure
relief valve
DHW expansion vessel
Pressure
reducing
valve
Filter
Stop valve
Mains
water
supply
Cold water supply
These components are supplied
in separate box with boiler
Diverter
valve
Check
valve
Resistance created
by each elbow
or bend
0.8 m
1.0 m
1.4 m
Maximum resistance allowed,
expressed as a length of straight
pipe (i.e. no elbows or bends)
up to 9 m
up to 18 m
up to 27 m
Minimum size of discharge
pipe 'D2' from tundish
22 mm
28 mm
35 mm
Minimum size of discharge
pipe 'D1' to tundish
15 mm
Valve
outlet size
G½
Sizing of copper discharge pipe 'D2' - refer also to Fig. 9
Fig. 8
Discharge pipe - The discharge pipes from the temperature/pressure and expansion relief valves must be routed to the
tundish supplied and in 15 mm pipe. The discharge pipework from both relief valves may be joined together in the same sized
pipe, providing at least 22 mm pipework is connected downstream of the tundish.
Tundish - The tundish must be positioned within 500 mm horizontally of the temperature/pressure relief valve, so that it is visible
to the User and away from electrical devices. The minimum size of the discharge pipe downstream of the tundish is given in the
following table.