COMMISSIONING THE POWER FLUE SYSTEM
THE INSTALLER MUST COMMISSION THE POWERFLUE SYSTEM AS PER CLAUSE H2.2.7
The correct CO2concentration shall be established by adjustment of dampers and checked by flue
gas analysis. A check that the controls are operating in the manner specified shall be carried out.
The check shall include a simulation of fan failure.
Commissioning the powerflue systed is an additional requirement to commissioning the appliance.
The appliance must also be commissioned as per AS5601.1.2013.
Sizing of the fan
In order to select a suitable fan, it is necessary to determine the volume and temperature of the
flue gases. Before this can be done the percentage of CO2in the flue gases shall be decided.
If discharge is at a low level, 1% CO2may be used in the design formula. For other situations,
values between 4% and 8% may be used. These values will give flue gas temperatures of 140°C
and 220°C respectively.
For appliances with modulating burners, the CO2concentration in the flue shall be considered
when the appliance is operating at normal rate, i.e. 8% CO2in the combustion chamber.
The quantity of flue gases to be handled by the fan may be determined by the following simplified
formula, which is sufficiently accurate for most flue gases currently distributed. A suitable fan may
then be selected.
Where Q = volume of flue gases, litres per second
T = total gas consumption of appliances connected to flue megajoules per hour
R = desired % CO2concentration by volume in the flue gases at the discharge point
FLUE GASES - RELATIONSHIP BETWEEN % CO2VOLUME FLOW RATE & % EXCESS AIR
CO2% Volume Flow Rate L/s/MJ/h Excess Air %
10 0.10 33
9 0.11 50
8 0.13 67
7 0.14 90
6.7 0.15 100
6 0.17 120
5 0.20 170
4.4 0.23 200
4 0.25 230
3.3 0.30 300
3 0.33 400
2.2 0.45 500
2 0.50 500
1.7 0.60 700
1.2 0.80 1000
1.0 1.00 1200
0.8 1.20 1500
0.6 1.60 2000
0.5 2.00 2600