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7. System
The system must comply with requirements of BS6798 and
BS5449.
General:
The appliance is only suitable for connection to indirect fully
pumped sealed and open vent systems. The minimum static
head is 1.2m and the maximum is 30m.
The pump MUST be wired to the boiler control to ensure that the
pump-overrun function operates to prevent the risk of
overheating and hence nuisance shutdown.
The controls must be wired to ensure that the boiler does not
cycle when electronically controlled zone valves are closed.
A by-pass is required if the controls i.e. 2-port valves, can result
in the closure of the CH and DHW circuits when the boiler is hot.
If mechanically operated thermostatically controlled valves are
fitted on all radiators then a by-pass located at least 2m from the
boiler is required.
A bypass is generally unecessary on a system using a 3 way diverter
valve as one port will be open to flow at all times. This will be
satisfactory for the pump overrun requirement. However if TRV's are
used throughout then a bypass or open radiator may be necessary.
Sealed System:
A sealed system must include an expansion vessel, pressure
relief valve and pressure gauge - these are available as
proprietary kits, the sealed system expansion vessel and fittings
must be connected at the neutral point of the system on the
entry to the pump. A pump and diverter valves are also required
as appropriate to the system. Refer to Fig 5,6,7.
The sealed system must be filled through a WRc approved filling
kit. Refer to Fig.8. The approved method for temporary
connection for filling a closed circuit in a house can be found on
Page 8.25. Fig R24-2a of the Water Regulation Guide and Water
Bylaws 2000 Scotland.
The appliance must not be operated without the system being
full of water and correctly pressurised.
All connections in the system must withstand a pressure of up to
3 bar.
The system and the appliance must be properly vented.
Repeated venting loses water from the system and usually
indicates that there is a leak.
Fig. 5. System layout if using Honeywell 'Y' plan
Feed and
Vent Cistern
Heating vent
(22mm min.)
Boiler
Primary
S.H.
cold feed
(15mm min.)
150mm max
8. Domestic Hot Water
The appliance is NOT suitable for direct water supply.
Do not connect to a direct cylinder.
The CBi can be connected to any indirect cylinder, i.e unvented or
thermal store, and all the benefits of a "dry loft" and mains
pressure hot water can be realised. Contact The Worcester
Technical Helpline. 08705 266241.
Cylinder
Indirect coil type or a direct cylinder with an immersion calorifier
that is suitable for a pressure of 0.35bar above the setting of the
pressure relief valve. Single feed indirect cylinders are NOT
suitable for sealed systems. Any connection to the mains water
supply must conform to the relevant Building and Water
Regulations and be approved by the local Water company.
Domestic hot
water cylinder
Diverting
valve
Pump
Bypass or
uncontrolled
radiator
(if required)
8
For system wiring please refer to
Fig. 10. and the controls
manufacturers details.
S.H. – Minimum static head 1.2m
measured from the highest point in the
heating system (top surface of the appliance
S.H.
or highest point in the heating system) to the
water level in the feed and expansion tank
N.B. A drain cock should be
installed at the lowest point of
the heating circuit
Radiator
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