12
4000123944-2
• Copper tubing or plastic Hep
2
0 may be used for the domestic
hot water system. Unecessary pressure losses should be
avoided.
• Provision shall be made for a drain valve at the lowest points
of the system.
• The flow restrictor must be fitted limiting the flow through the
boiler to a maximum of 12 l/min.
• The boiler will operate with a minimum supply pressure of 0,5
bar, at reduced flow rate.
Best operating comfort will be obtained from a supply pressure
of 1 bar.
4.1 Hard Water Areas
In areas where the water is 'hard', more than 200mg/litre, it is
recommended that a proprietary scale reducer is fitted in the
cold water supply to the boiler.
4 Domestic Hot Water System Design
0
10
20
30
40
50
60
70
0 200 400 600 800 1000 1200 1400
Flow rate through heating system l/h
Available pressure (kPa)
between heating supply and return
1
2
3
4
5
11357
(10 kPa = 1 m WG)
1
2
3
4
5
Bypass fully shut
Open 1/4 turn
Open 1/2 turn
Open 1 turn
Open 2 turns
Diagram 3.1
Diagram 3.2
10015
Flow
control valve
Drain point
Bypass
valve
Domestic
water
Heating
circuit
Return
Additional
expansion
vessel
(if required)
Boiler
Hot
Cold supply
Filling device
Bypass
(If required)
*
*
'A'
3 Heating System Design
3.1 Bypass
•The boiler is fitted with an adjustable automatic bypass.
Ensure that under no circumstances does the flow rate drop
below the figure specified, see Table 1.
• A bypass is not required on the central heating circuit unless
the system controls could allow the boiler to operate when
there is no flow.
• Where a bypass has to be fitted, the bypass must be placed
at least 1.5 metres from the appliance, see diagram 3.2.
3.2 Filling the system
A filling device is fitted to the boiler to initially fill the system and
replace water lost during servicing, see the relevant parts of
diagram 2 controls and lighting and diagram 3.2.
TABLE 1. FLOW RATE
Model Minimum flow rate
30ci plus 21.26 litres per minute
This is equal to 20°C differential at maximum heat input
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