4. INTRODUCTION OF THE COMBI BOILER
4.3 Circulation Pump Performance Curve
Pump pressure specifications for sealed central heating system are shown at the following chart.
Pump pressure heigth should be considered during calculation of the sealed central heating system water pipes diameters.
If there has been no heating demand for 24 hours the boiler will run the system pump for 30 seconds to reduce the possibility
of pump blockage. The mains power must be on to enable this function to operate even the combi boiler is switched off.
The combi boiler pump has three speeds as shown below;
1. Stage
2. Stage
3. Stage
QH Chart
Q (m
3
/h)
6
5
4
3
2
1
0
0.5
1.0
1.5
2.0
2.5
H(m)
4.4 Water Circulation System
A. Mains Water Filling Valve
B. Flow Control Valve
C. 3 Bar Safety Valve
D. Circulation Pump
E. Automatic Air-venting Valve
F. Expansion Vessel
G. Air Pressure Controller
H. Gas Flue
I. Fan
J. Central Heating Water Sensor
K. Limit Temperature Sensor
L. Heat Exchanger
M. Gas Burner
N. Gas Valve
0. By-Pass
P. Closed Circuit Pressure Switch
Q. Domestic Hot Water Sensor
R. Mains Cold Water Inlet
S. Domestic Hot Water Outlet
T. Central Heating Water Flow
U. Central Heating Water Return
V. Gas Inlet
35
88
35
55
!
0
2
60
30
0
90
120
bar
0
1
3
4
o
o
C
H
G
L
M
B
F
C
O
P
E
D
U
R
N
V
S
T
Q
J
K
A
i
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