Installation; Important Remarks; Sealed Systems - Benchmark ZB 7-28 R 28 HE Installation And Servicing Instructions

Wall mounted condensing boiler for central heating
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3

Installation

B Always turn off the gas cock before car-
rying out any work on components
which carry gas.
Fixing of the appliance, gas and flue con-
i
nections, commissioning of the system
and electrical connections may only be
carried out by competent persons author-
ised by CORGI.
3.1

Important remarks

B Appliance should only be installed in sealed central
heating systems.
B To avoid gas formation in the system, galvanised radi-
ators or pipes must not be used.
B If a room thermostat is used: do not fit a thermostatic
radiator valve on the radiator in the primary room.
B Add a suitable anti-freeze fluid compatible with alu-
minium to the water in the central heating system.
Suitable products are available from Betz-Dearborn
Tel.: 0151 4209563, Fernox Tel.: 01799 550811
and Salamander Tel: 0121 378 0952.
B In our experience, the addition of sealing agents to
the water in the central heating system can cause
problems (deposits in the heat exchanger). For that
reason we advise against their use.
6 720 611 443 GB (05.04)
3.2

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 and is
charged to a pressure of 0.75 bar.
The water capacity of the system is shown in table 12,
page 27. 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 fig. 8.
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.
Fit Thermostatic Radiator Valves to radiators in the
sleeping accommodation and not to the radiator where
the room thermostat is sited, this must be 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 Superconcen-
trate 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.
Suitable products are available from Betz-Dearborn Tel:
0151-4209563 and Fernox Tel: 01799-550811.
A drain cock to BS2879 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 appli-
ance. Thoroughly flush the heating system and
the mains water supply before fitting the appli-
ance to the wall in accordance with the recom-
mendations of BS7593:1992.
Installation
11

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