Technical data
43
Caution: On windy days or on installations with a long flue run it is necessary to
replace the front cover of the boiler in order to obtain an accurate CO
2
measurement
Setting the gas valve by pressure measurement
This method is less accurate, but usually gives a sufficient result.
1. Switch off the appliance using the On/Off button (
-
on service display).
2. Remove the front cover of the appliance.
3. Turn the measuring nipple (C) on the gas valve open with two turns and connect
this through a tube to the plus connection of the pressure gauge.
4. Switch on the appliance using the On/Off button.
5. Set the boiler to the lowest output by simultaneously pressing the “Service” and “–“
buttons on the operating panel until an
L
appears on the service display.
6. Read the pressure. This should be about – 0.05 mBar (between – 0,1 mBar and 0
mBar). When this is not the case, proceed as follows for setting:-
7. Remove the dust cap (A) with a torx T15 driver.
8. Set the pressure using setting screw (B) (clockwise higher and counter-clockwise
lower).
9. After measuring and setting, replace the cover cap A and close the measuring
nipple (C) again.
10. Remount the front cover of the appliance.
Caution: Check the measuring nipple (C) for gas tightness.
7.10 Carbon monoxide : carbon dioxide ratio (CO/CO
2
ratio)
Atmos recommends that a carbon monoxide : carbon dioxide ratio test is carried out
when the boiler is commissioned. This is best done when the CO
2
content of the flue
gasses is measured. See the procedure described in §7.9.
The CO/CO
2
ratio at low or high output should be no higher than 0.004.
A CO/CO
2
ratio between 0.004 and 0.008 means that the appliance is ‘At Risk’ (AR).
A CO/CO
2
ratio above 0.008 means that the appliance is ‘Immediately Dangerous’
(ID)
Where an ‘at risk’ or ‘immediately dangerous’ situation is encountered, measures must
be undertaken to rectify the situation. Particular attention should be given to the gas/air
ratio, the integrity of the flue, or blockage in the heat exchanger. Contact the
manufacturer for assistance.