Product specifications

The annual inspection of the boiler comprises the
following:-
1. Visual inspection of the flame
2. Measuring the gas rate.
3. Measuring the O2 or CO2 concentration in the
flue gas.
4. Measuring the CO/CO2 ratio.
5. Inspecting the ionisation flow.
6. Inspecting the siphon.
1. Visual inspection of the flame
The flame must be assessed after one minute of
ombustion at the low position or high position.c
 Low position
Viewed from top to bottom on the combustion seat,
the burner flame picture must have the presence of
a light blue flame.
A completely red flame indicates that the supplied
air/gas mixture is gas rich; an entirely dark blue
flame indicates an air rich mixture.
If the flame picture is correct, there is no need to
measure the O
2 or CO2 concentration of the flue
gas, and point 3 of the inspection can be left aside.
If the flame picture is not correct, the O
2 or CO2
percentage of the flue gas must be measured.
 High position
Viewed from top to bottom on the combustion seat,
the burner flame picture must have the presence of
an entirely blue flame. When the low position
flame is set correctly, the high position flame will
be correct. No separate adjustment is made.
If the flame picture is not correct, the O
2 or CO2
percentage of the flue gas must be measured.
2. Measuring the gas rate.
Check the burner's gas rate by stopwatch and meter.
On the boiler’s maximum burner input of 24kW,
32kW or 38kW (depending on boiler model), the
time taken to use 0.024 m³ (0.847 ft³), 0.032 m³
(1.130 ft³) or 0.0378 m³ (1.335 ft³) of gas
respectively should be 33 seconds (± 2seconds).
See also Section 8.3 for alternative figures for 1 ft³
(or litres for metric meter).
Note! If the flue's 80mm diameter gas discharge
duct is longer than 10 metres, the gas rate can be
reduced. The measured time will in this case
increase by up to 2%.
Record the measured value on the appliance service
card. Compare the measured time with the value(s)
recorded last time the appliance was put into
operation and/or the previous annual inspection.
If the measured time falls outside of the tolerances,
inspect the air supply and flue gas discharge system
and the heat exchanger of the appliance for soiling,
and clean where necessary (see Section 10.3).
3. Measuring the O
2 or CO2 concentration of the
flue gas.
Note! The inspection results and any
servicing work undertaken should be noted
on the Service card located on the front of
the hot water storage tank insulation shells.
The O
2 or CO2
measurement of the flue gas must
be undertaken using an analyser calibrated to a
precision of < 0.2%.
Flue gas samples can be taken from the test hole at
the left-hand side of the outlet casing.
Set combustion at high or low rate by entering the
service program.
1) Press and hold the 'Set' button on the controller
for 10 secs until a capital 'A' appears on the central
heating display.
2) By pressing the 'Hot water' button, it is possible
to scroll between the low rate, high rate and an
indication of the strength of flame ionisation. (See
inspection point 4).
3) With the burner set to a low rate (LL), sample
the flue gases. The CO
2 measurement should be
within the limits given in Table 6. Correct the
measured value by adjusting the gas valve regulator
(Fig 36 ). Remove the dust cap using a 4mm
hexagonal wrench (or No 25 Torx driver). Turn the
regulator screw beneath by small increments to
bring the figure within the range of Table 6;
clockwise to increase the gas supply and thus the
CO
2 content, and anticlockwise to decrease the
CO
2 content. Once the low rate is set, check the
CO
2 content is correct at the high rate (HH).
Should the high position be outside the range
tolerated, return to the low position, correct the
setting and return to high to recheck the CO
2
measurement. Record the data on the Service card.
Table 6. O
2 and CO2 limits
NOTE: The above is for Natural gas. Atmos
provide a separate sheet covering propane (Propane
Conversion).
ATMOS MULTI Mk 2 version 2008
Page 39