SERVICE AND SPARES
6 720 803 800 (2012/11)
38
6.5
FAN PRESSURE TEST
Before setting the boiler to maximum output for the fan pressure test,
refer to figure 74:
▶ Switch the boiler off.
▶ Remove the combustion air intake pipe (1).
▶ Remove the fan pressure test point cover (2).
▶ Connect the digital manometer pipe (3) to the fan pressure test point
(4).
▶ Replace the combustion air intake pipe.
▶ Switch the boiler on.
▶ Set the boiler to maximum output.
6.5.1
SETTING THE BOILER TO MAXIMUM
To set the boiler to maximum output, refer to figure 73:
1. With the control panel in the operating position, press and hold the
and
buttons together for at least five seconds.
– The chimney sweep symbol (1) will be displayed at the top of the
screen.
– The word Max will flash at the bottom of the screen.
– The boiler will take approximately 30 to 35 seconds to ramp up to
maximum output.
– Allow the boiler to stabilise at maximum output.
▶ Ensure that the fan/gas valve do not modulate.
Fig. 73 Set boiler to maximum
6.5.2
FAN PRESSURE
▶ Remove the combustion air intake pipe [1]
▶ Remove the cover [2] from the fan pressure test point [4]
▶ Connect the pipe [3] from the digital manometer to the fan pressure
test point [4]
▶ Refit the combustion air intake pipe
Fig. 74 Fan pressure test point
With the combustion air intake pipe fitted and the boiler running at
maximum output, measure the fan pressure:
▶ The pressure will read negative, refer to the chart in figure 75 below.
Fig. 75 Fan pressure readings
▶ If the manometer reading is in the white area of the chart the heat
exchanger/exhaust path/siphon does not require attention.
▶ If the manometer reading is in the black area of the chart then carry
out the following checks:
– Check that the siphon is not blocked.
– Check the exhaust paths for restrictions.
– Clean the heat exchanger with a suitable cleaning tool, refer to
section 6.7 - Cleaning the heat exchanger.
▶ Re-check the fan pressure readings.
If the boiler, after completing the above checks, fails the fan pressure
test then contact Worcester, Bosch Group for advice.
▶ After the measurements are taken switch the boiler off.
▶ Remove the combustion air intake pipe.
▶ Disconnect the manometer and replace the test point cover.
▶ Replace the combustion air intake pipe.
Allowed mbar pressure drop
meter/
regulator
across
pipework
boiler inlet
across
boiler
gas control
valve
Natural gas
19 - 23
1
18 - 22
1.5
16.5 - 20.5
L.P.G.
32 - 45
2.5
29.5 - 42.5
1.5
28 - 41
mbar range
This test is to determine if the heat cell requires cleaning
or attention.
When running at maximum output, and the water
temperature is 65°C or less, the boiler will operate both
the central heating and DHW circuits with the diverter
valve in the mid position. It will be necessary to run
sufficient water through the DHW circuit to ensure that
the boiler will not cycle on low heating demands.
This is to allow sufficient time for the setting procedure.
When the water temperature reaches 75°C the diverter
valve will switch to CH only.
eco
max
min
2
3
1
0
4
bar
1
ok
eco
reset
e
max
min
°C
°F
Max
6720646608-45.1W
o
°C
°F
Max
1.
1
≈≈
5 s
5 s
NOTICE:
Fan pressure test
▶ The boiler must be run at maximum output for the fan
pressure test and flue gas analysis.
6720646608-50.3W
o
1
2
4
3
6720803800-05.1W
o
FAN PRESSURE TEST
Clean the Heat Ex.
Heat Ex. ok
0
-6
-5
-4
-3
-2
-1
-8
-7
mbar
NG Boilers
32kW:
36kW:
28kW:
- 4.4
- 5.4
- 3.5
0
-6
-5
-4
-3
-2
-1
-8
-7
mbar
LPG Boilers
32kW:
36kW:
28kW:
- 4.4
- 5.4
- 3.5
