Commissioning; Checking The Gas Inlet Pressure - Worcester 27i System Compact Installation, Commissioning And Servicing Instructions

COMMISSIONING

5.5 COMMISSIONING
NOTICE: The combustion settings on this gas-fired boiler
have been checked, adjusted and preset at the factory for
operation on the gas type defined on the data plate.
No measurement of the combustion values is necessary
provided there is a meter installed allowing the gas rate to
be checked.
DO NOT ADJUST THE AIR/GAS RATIO VALVE.
If the optional integral diverter valve is fitted (not
supplied) and the Service mode and maximum output are
selected the boiler will operate both the Central Heating
and DHW circuits with the diverter valve in the mid
position. 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.
For S and Y plan systems only use the Central Heating
circuit.

5.5.1 CHECKING THE GAS INLET PRESSURE

The inlet pressure to the appliance must be checked using the following
procedure:
MEASURING THE INLET PRESSURE
1
Fig. 59 Inlet pressure test point
▶ Close gas isolation valve.
▶ At the inlet test point (1), slacken the screw for a maximum of half a
turn and connect a manometer.
▶ Open gas isolation valve.
▶ Measure the pressure with the boiler running at maximum.
– Press the and button for more than five seconds and the
eco
boiler will ramp up to maximum output in approximately 30 to 35
seconds.
– The display will show the chimney sweep symbol and the word
MAX.
34
≈ ≈
5 s 5 s
eco
°C
reset ok
°F
Max
1.
e
min max
Fig. 60 Setting boiler to maximum
▶ Check the gas supply working pressure at the gas valve conforms to
values shown in Fig. 61or Fig. 62.
▶ Press the button to return to normal operation.
▶ The boiler will run for 15 minutes in service mode and return to normal
if no other inputs are made.
Ensure that the inlet pressure is satisfactory with all
other gas appliances working.
After the tests are completed:
▶ Disconnect the manometer.
▶ Re-tighten, but do not overtighten the inlet pressure test point screw.
Check for gas tightness
GAS PRESSURE WITHIN THE SYSTEM
Refer to the figures below for natural gas or L.P.G gas pressures.
The working pressure at the boiler must not be less than the working
pressure read at the meter minus 1mbar for natural gas or minus
2.5mbar for L.P.G.
The pressure drop from the meter to the gas valve must not be more than
2.5mbar for natural gas or 4mbar for L.P.G.
If the pressure drop is greater than shown below, then this would
indicate a problem with the supply pipework which must be rectified.
Meter
Natural Gas
< 2.5mbar
difference
19 - 23 mbar
Boiler inlet
1 mbar
drop
18 - 22 mbar
Fig. 61 Natural gas pressures
Greenstar i System Compact - 6 720 807 726 (2013/05)
2
1 1
3
0 bar 4
1
min max
°C
°F
Max
Gas Control
valve
16.5 - 20.5 mbar
1.5 mbar
drop
6720644744-44.2Wo