Worcester Greenstar 12Ri Technical Information page 21

Open vented primary systems
The Greenstar regular boiler range is designed for
connection to an open vented fully pumped heating and
hot water system.
The following points are for guidance only. The system
installation should be carried out in accordance with
BS 5449:Part 1.
The cistern must be arranged to provide a minimum static
head of 0.25 metres above the top of the highest point in
the heating circuit.
Air in the appliance is expelled through the vent pipe or
dissipated into the system. Manual air vents should be
fitted at any high points in the system.
Y plan
F & E
AAV
IV HC IV
MPV
or
DIV
BC
B
PR
S plan
F & EC
AV
IV HC IV
ZV
ZV
ABV
BC
B
PR
Air supply
Worcester Greenstar regular boilers are room sealed
appliances; the room in which it is installed does not
therefore require a purpose provided combustion air vent.
RT
CYL
CT
R
W V LSV
RT
CYL
CT
R
W V LSV
Natural gas supply
For the Greenstar Ri series when on a full output
demand will require up to 3.02m
on the model).
For the Greenstar CDi Classic Regular series when on
a full output demand will require up to 4.4m
(depending on the model).
The gas meter and supply pipes must be capable of
supplying this quantity of gas in addition to the demand
from any other appliance being served. The meter outlet
governor should be capable of ensuring a dynamic nominal
pressure of 20mbar (8in wg) at the appliance. Particular
consideration should be given to the resistance to gas flow
created by elbows, bends etc. Pipework should be sized
to overcome this resistance, and details of this are given in
the following table.
Total length of
gas supply pipe (m)
3
Gas 2.9
discharge
8.7
/h
rate m
3
18.0
*Greenstar 12Ri and 15Ri series only.
Approximate additional length to be allowed (natural gas)
Elbows or tees
Metres Feet
0.5 2
Greenstar 12Ri and 15Ri models
Provided that the correct gas supply working pressure and
gas rate can be achieved (refer to BS 6891) then it may be
possible to reduce the gas supply pipe diameter to 15mm.
Generally speaking, the appliance would need to be within
3 to 4 metres of the gas meter. However, this will depend
on the distribution pipe size and route.
Greenstar 18Ri, Greenstar 24Ri and
Greenstar CDi Classic Regular models
Under no circumstances should the size of the gas supply
pipe be less than 22mm.
/hr of gas (depending
3
/hr of gas
3
Pipe diameter
(mm)
6 9
– –
5.8 4.6
12.0 9.4
90º bends
Metres
0.3
–
15*
22
28
Feet
1
21