Checking The Gas Inlet Pressure; Fan Pressure Test; Setting The Boiler To Maximum; Fan Pressure - Worcester Greenstar 25Si Compact Installation, Commissioning And Servicing Instructions

SERVICE AND SPARES
7.4

CHECKING THE GAS INLET PRESSURE

NOTICE: Gas inlet pressure
▶ Do not continue with the other checks if the correct
gas pressure can not be achieved.
▶ Refer to section 6.5.1 and check that the gas working pressures in the
system conform to the figures shown below:
Allowed mbar pressure drop
meter/ across boiler inlet
regulator pipework
Natural gas
19 - 23 1 18 - 22
L.P.G.
32 - 45 2.5 29.5 - 42.5
mbar range
7.5

FAN PRESSURE TEST

This test is to determine if the heat cell requires cleaning
or attention.
Before setting the boiler to maximum output for the fan pressure test,
refer to figure 67:
▶ 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.

7.5.1 SETTING THE BOILER TO MAXIMUM

To set the boiler to maximum output, refer to figure 66:
1. With the control panel in the operating position, press and hold the
and buttons together for at least five seconds.
eco
– 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.
≈ ≈
5 s 5 s
eco
°C
reset ok
°F
Max
1.
e
min max
Fig. 66 Set boiler to maximum
42
across gas control
boiler valve
1.5 16.5 - 20.5
1.5 28 - 41
2
1 1
3
0 bar 4
1
min max
°C
°F
Max
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.

7.5.2 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
1
4
3
2
Fig. 67 Fan pressure test point
NOTICE: Fan pressure test
▶ The boiler must be run at maximum output for the fan
pressure test.
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 68 below.
FAN PRESSURE TEST
Clean the Heat Ex.
NG Boilers
25Si: - 2.7
- 3.8
30Si:
0 -1 -2 -3
LPG Boilers
25Si:
- 2.7
30Si: - 3.8
0 -1 -2 -3
Fig. 68 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 7.7 - Cleaning the heat exchanger.
Greenstar Si Compact
Heat Ex. ok
-4 -5 -6 -7 -8
mbar
-4 -5 -6 -7 -8
mbar
ErP - 6 720 813 278 (2015/07)