Benchmark Metropolis DGT 25 BF, Installation And Servicing Instrucnion

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2.9.1 Pump
The available head shown in fig. 5 is that in
excess of the appliance hydraulic
resistance, i.e. that available for the system
at any given heating load up to the
maximum output in C.H. mode. Never
reduce the pump speed below maximum as
this will reduce D.H.W. output. The pump
speed is indicated on the side of the pump
speed selector switch (if fitted).
2.9.2 System volume
(total water content)
The Table 4 gives the maximum system
volume that the integral expansion vessel
can sustain under different charge
pressure conditions.
If the system volume exceeds that shown,
an additional expansion vessel must be
fitted and connected to the heating system
primary return pipe as close as possible to
the appliance.
If an extra vessel is required, ensure that
the total capacity of both vessels is
adequate. Further details are available in
the current issues of BS5449 and BS6798.
NOTE: If the pressure gauge indicates
2.65 bar or greater when the appliance is
at maximum temperature with all
radiators in circulation an extra
expansion vessel is required.
2.9.3 Pressure gauge
A pressure gauge is mounted in the base of
the appliance.
2.9.4 Safety valve
A safety valve set at 3 bar is fitted to the
appliance and a discharge pipe is routed to
outside of the appliance.
This discharge pipe should be extended to
terminate safely away from the appliance
and where a discharge would not cause
damage to persons or property but would
be detected.
The pipe should be able to withstand boiling
water, be a minimum of 15 mm in diameter,
and installed with a continuous fall.
2.10 D.H.W. SYSTEMS
– Check that the mains supply pressure is
within the prescribed limits (1.3 point).
If necessary, a pressure reducing valve
should be fitted to the mains supply
before the D.H.W. inlet connection.
– A maximum D.H.W. flow rate of 11.4 l/m
(3.0 gpm).
Higher flow rates will not damage the
appliance but may lower the water
temperature below an acceptable level.
– If the appliance is installed in an area
where the temporary hardness of the
water supply is high, say over 150 ppm,
the fitting of an in line scale inhibitor may
be an advantage. Consult the Local
Water authority if in doubt.
2.10.1 Domestic hot/cold water supply
taps and mixing taps
All equipment designed for use at mains
water pressure is suitable.
2.10.2 Showers
Any WRAS approved shower suitable for
the mains water pressure available may be
used. A loose or flexible shower head type
may require the fitting of an anti-syphon
device to comply wth water by-laws.
2.10.3 Bidets
Providing that the appliance is of the over-
rim flushing type, the outlets are shrouded
and it is impossible to attach a temporary
hand held spray, no anti syphonage device is
necessary.
2.11 FILLING THE WATER SYSTEM
– Open the C.H. flow and C.H. return valves
(3 - fig. 3).
– Loosen the automatic air vent cap (8 fig.
2).
– Open all radiator valves and system air
vents. Fill the system with water using
one of the approved methods described
in section 2.9 to about 0.5 bar greater
than the system design pressure. Close
all air vents. Do not close the A.A.V. the
one near the pump!
– Check the system for water soundness.
– Completely drain the appliance and
heating system, thoroughly flush the
system, and refill the system design
pressure to BS 7593.
– Open the D.H.W. inlet valve, open any hot
tap, clear of air bubbles.
– Close hot tap.
2.11.1 Emptying the system
Use the cock boiler discharge to empty the system
(15 fig. 2). Turn off the boiler before draining.
2.12 ANTI-FREEZE FUNCTION
The boilers are equipped with anti-freeze
function which activates the pumps and the
burner when the temperature of the water
contained inside the appliance drops to
below value set at PAR 10. The anti-freeze
function is ensured, however, only if:
– the boiler is correctly connected to the
gas and electricity supply circuits;
– the boiler is constantly fed;
– the boiler ignition is not blocked;
– the essential components of the boiler
are all in working order
In these conditions the boiler is protected
against frost down to an environmental
temperature of -5°C.
ATTENTION:
In the case of installation in a place where
the temperature drops below 0°C, the
connection pipes must be protected.
2.13 APPLIANCE PACKAGE:
– Combination boiler (assembled);
– Installation and servicing instructions;
– Users instructions;
– Wall mounting templates (paper);
– Fixing screws with wall plugs;
– Plastic bags containing:
– gas service cock;
– C.H. F/R isolation valves;
– D.H.W. isolation valve;
– D.H.W. outlet fittings;
– associated gaskets and PRV discharge
pipe.
2.14 WATER CONNECTIONS
2.14.1 Central heating
connections
– Fit the two C.H. isolation valves using the
gaskets supplied to the flow and return
connections as shown in fig. 2. The pipe
connections are labelled on the lower
part of the boiler.
– Connect the C.H. pipework as required.
2.14.2 D.H.W.
connections
– Fit the D.H.W. isolation valve to the cold
water inlet connection as shown in fig. 2.
– Fit the union connection to the D.H.W.
13
ENG
IT
ES
Vessel charge and initial system pressure
bar
psi
0.5
7.3
1.0
14.5
1.5
21.8
Total water content of system using 8 l (1.76 gal) capacity
expansion vessel supplied with appliance
l
gal
96
21.1
74
16.2
51
11.2
For systems having a larger capacity multiply the total system
capacity in litres (gal) by the factor to obtain the total minimum
expansion vessel capacity required litres (gal)
.0833 .109 .156
TABLE 4