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INSTALLATION DESIGN AND PLANNING INFOrMATION
3.6. SYSTEM / BOILEr PuMP
The variable duty pump should be fitted on the flow pipe from the boiler
and have isolating valves on each side as shown schematically in diagrams
3.3 and 3.4.
The pressure loss characteristics of the boilers are shown in diagram 3.9. The
water flow rates and the boiler pressure losses at 11ºC and 0ºC temperature
differences are also tabulated below in table 3.4.
The variable duty pump should be set to give a temperature difference of no
greater than 0ºC between boiler flow and return to give minimum flow rate
through the boiler shown in table 3.4. High resistance micro bore systems may
require a higher duty pump.
Diagram 3.9 Pressure loss characteristics of the boilers
4.5
4.0
3.5
3.0
2.6 m
2.5
2.0
1.9 m
1.5
1.3 m
1.0
0.8 m
0.5
0.0
0
100
200
300
400
500
GB-10
10kW = 430 l/h at 20K diff
3.7. FLOW rATE
If it is necessary to alter the flow rate in a system, the system can be fitted with
a lockable balancing valve in the main flow or return pipes. The example is
shown as a valve 'A' in diagram 3.4.
The flow rate through the boiler must not be allowed to fall below the values
given in table 3. for the boiler model selected.
Table 3.4 Boiler pressure loss data
Boiler
Temperature
Model
difference (K)
GB30
11
0
GB5
11
0
GB0
11
0
GB15
11
0
GB10
11
0
600
700
800
900
1000
1100
Flow rate (litres/h)
GB-25
25kW = 1070 l/h at 20k diff
GB-15
GB-20
15kW = 640 l/h at 20K diff
20kW = 850 l/h at 20K diff
Flow rate (Litres
Pressure loss (m WG)
per hour)
34
188
1951
1073
1561
858
1171
644
780
49
3.8. BYPASS vALvE
A bypass is not required on the central heating system
unless the system controls could allow the boiler and
the pump to operate when there is no flow.
When a bypass valve has to be fitted, it must be placed
at least 1.5 meters away from the boiler as shown
schematically in diagrams 3.3 and 3.4. An automatic
bypass valve is recommended.
3.9. DOMESTIc HOT WATEr
STOrAGE cYLINDEr
Single feed indirect cylinders are not suitable.
The domestic hot water cylinder must be of the double
GB_10, GB_15
feed fully indirect coil type. It must be suitable for
working at a gauge pressure of 0.35 bar above the
safety valve setting.
GB_20, GB_25, GB_30
The storage vessel does not have a vent to the
atmosphere i.e. unvented cylinder is used, then the
installation must comply with the Building regulations
and Local Water Company bylaws. See also the current
issues of BS5546 and BS6700.
3.10. BOILEr LOcATION AND vENTILATION
1200
1300
1400
1500
GB-30:
30kW = 1280 l/h at 20K diff
3.10.1. Boiler Location
The boiler may be installed in any room although
particular attention is drawn to the requirements of the
current issue of BS7671 with respect to the installation
of a boiler in a room containing a bath or a shower.
Any electrical switch or boiler control using mains
electricity supply should be so sited that a person using
the bath or a shower cannot touch it. The electrical
provisions of the Building Standards (Scotland)
Regulations are applicable to such installations in
Scotland.
These boilers are not suitable for fitting outdoors.
The boiler must be mounted on a flat wall, which is
sufficiently robust to take its total weight given in
table 3.1.
6.66
.30
4.79
1.69
3.
1.17
3.91
1.47
.00
0.80
Page 16
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