4. Service & Replacement of Parts
To ensure safe, efficient operation of the boiler, it is
necessary to carry out routine servicing at regular
intervals. The frequency of servicing will depend upon
the particular installation conditions and the use to which
the boiler is put.
Important: Before commencing any servicing or
exchange of components, always turn off the gas
supply and isolate the electricity supplies (i.e. to
boiler and immersion heater).
Annual servicing is recommended. After completing any
service wor
k
always test for gas soundness and
Remember to fill in the Benchmark Checklist.
To gain access to the boiler for servicing, remove front
panel and top cover as described in Section 4.
1
.
Annually
Important
: Any
'
O
'
rings, seals, gas
k
ets or washers
disturbed during service or replacement of parts must
be visually inspected and replaced if worn or
damaged.
1
. Remove outer and inner top covers to gain access
to heat exchanger etc. Inspect components within
compartment, chec
k
ing that joints are dry etc.
2. Remove the heat exchanger door complete with
burner, see Section 4.
1
4. Inspect the burner,
combustion chamber and heat exchanger, carefully
clean using a vacuum cleaner. DO NOT separate
the burner from the heat exchanger door. Inspect
the electrode condition and chec
k
gap which
should be 4.
5
-
5
.
5
mm.
3. Withdraw the ionisation probe, clean with wire wool
or similar abrasive, replace if necessary. Re-fit heat
exchanger door.
4.
P
artially open vent on top of heat exchanger and
release any trapped air.
C
hec
k
that the cap on the
auto air vent (on top of pump) is partially
unscrewed.
5
. Draw hot water from a bath tap if necessary to
cause burner to light.
C
hec
k
ignition is smooth and
visually inspect flame.
C
ontinue to draw water until
maximum fan speed is attained.
C
hec
k
combustion, see
C
ombustion Testing.
6. Turn off the mains water supply at the Inlet
C
ontrol
Group and release system pressure by opening a
hot tap. Using hexagon
k
ey provided, remove the
pressure reducing cartridge from the Inlet
C
ontrol
Group.
C
lean the cartridge and strainer in running
cold water. Re-fit the cartridge ensuring that the
strainer is correctly located.
7
. With no water pressure in the system, chec
k
and if
necessary adjust the secondary expansion vessel
pressure to approx. 2.
5
to 2.
8
bar (36 to 40 psi).
NOTE:
Vessel pressure can not be accurately set
with water pressure in system.
8
. Restore pressure to DHW system. Manually
operate, in turn, the expansion relief valve (part of
Inlet
C
ontrol Group) and the temperature &
pressure relief valve (Fig.
1
0).
C
hec
k
that the
discharge route(s) is unobstructed and that water
flows freely to a safe, visible location.
C
hec
k
that
both valves close correctly.
9. Release
C
H system pressure via relief valve and
chec
k
primary expansion vessel pre-charge
pressure is between
1
.0 to
1
.2 bar. Adjust if
required and top up system to same pressure.
1
0.
C
hec
k
for gas soundness and re-assemble in
reverse order.
11
.
C
lean condensate trap by removing lower nut (see
section 2.4 Fig.
1
0a).
Combustion Testing
A combustion analysis test point is provided on the
flue outlet (just above heat exchanger). The test point
is sealed by a special screw/O ring assembly. For a
correctly installed boiler typical values to be expected
are:
C
O <
1
00 ppm
C
02 <9.2 % at maximum input
(Hot
condition after 10 minutes)
L
evels significantly above these should be
investigated and may indicate a defective component
or faulty installation. Ensure the test point is FU
LLY
GAS TIGHT. Do not substitute any other screw for the
special
P
romax
P
art No.
511
4
7
00.
34
© Baxi Heating UK Ltd 2015