Pre-Installation
13
Greenstar 4000 – 6 720 891 161 (2020/09)
Primary system considerations - Combi & System appliances
Sealed system
• The CH sealed system must be filled using a WRAS approved filling
loop or comply with examples in section 4.1.4 "System fill".
• Where the system volume is more than 100 litres or exceeds 2.5 bar
at maximum heating temperature an additional expansion vessel [2]
must be fitted as close as possible to the appliance in the central
heating return.
• Pressurise the extra expansion vessel [2] to the same value as the
built-in expansion vessel [1] (default pre-charge pressure is 0.75
bar).
Fig. 4 Additional expansion vessel
[1] Appliance expansion vessel
[2] Additional expansion vessel
[3] Pressure relief discharge
[4] Heating return
[5] Heating flow
Checking the size of the expansion vessel
To determine whether an additional expansion vessel is required: Follow
the steps below:
▶ Calculate the total system volume (litres).
– Plot a line vertically on the chart ( Fig. 5).
▶ Determine the central heating maximum operating flow temperature.
– Plot a line horizontally on the chart ( Fig. 5).
▶ Determine the pre-charge in the expansion vessel based on static
head, 1 metre = 0.1 bar.
– Static head should be measured between the expansion vessel
and the highest point on the system (top of the highest radiator).
▶ Select a curve from the key below (1-5).
▶ System pressure should be set at 0.1 - 0.25 bar higher than the
vessel pre-charge.
– It must be at least to the minimum on appliances with an analogue
gauge.
– Minimum pressure settings may need to be adjusted to suit on,
appliances with a digital gauge, in the applicable menu function.
– Intelligent filling settings may need to be adjusted to suit on,
appliances with the automatic filling accessory, in the applicable
menu function.
If the dissected lines are in area A then no additional expansion is
required.
If the dissected line is in are B then an additional expansion vessel must
be installed ( Fig. 4).
Fig. 5 Curves for the expansion vessel
1 Pre-charge pressure 0.5 bar (minimum)
2 Pre-charge pressure 0.75 bar
3 Pre-charge pressure 1.0 bar
4 Pre-charge pressure 1.2 bar
5 Pre-charge pressure 1.3 bar
A Operational capacity of the expansion vessel (left of the relevant
curve)
B Additional expansion vessel required (right of the relevant curve)
T Maximum operating temperature [ °C]
V Total System Volume [l]
The default pre-charge pressure for the expansion vessel is 0.75 bar
4.1.3 System layouts examples
Sealed primary system - Single central heating circuit:
Typical primary system example
Fig. 6 Single central heating circuit example
[1] Appliance
0010021117-001
3
4
5
2
1
0010036810-001
30
40
50
60
70
80
90
0 100 200 300 400 500 600 700
A
B
3
5
4
2
1
T[°C]
V[l]
1
0010021227-002
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