12
Installation and Servicing
SECTION 1 - GENERAL
Notes
a.
The method of filling, refilling, topping up or flushing sealed
secondary circuits from the mains via a temporary hose
connection is only allowed if acceptable to the local water
authority.
b.
Antifreeze fluid, corrosion and scale inhibitor fluids suitable for
use with HIU’s should be compatible with all the material present
in the appliance.
General
1.
The installation must comply with all relevant national and local
regulations.
2.
The installation should be designed to work with flow
temperatures of up to 84
o
C.
3.
All components of the indirect central heating system must be
suitable for a working pressure of 3 bar and a maximum design
temperature of 110
o
C. Extra care should be taken in making
all connections so that the risk of leakage is minimised.
The following components are incorporated within the appliance:
a.
Circulating pump.
b.
Safety valve, with a non-adjustable preset lift pressure of
3 bar.
c.
Pressure gauge, covering a range of 0 to 4 bar.
d.
An 8-litre expansion vessel, with an initial charge pressure
of 0.75 bar.
Note:
Direct units system must be capable of withstanding
the maximum design pressures of the attached primary
system.
Guidance on vessel sizing is given in table below.
Domestic Hot Water
1.
The DHW service must be in accordance with BS 6700.
2.
Refer to Table 1 for minimum and maximum working
pressures. In areas of low mains water pressures the
domestic hot water regulator may be removed from the DHW
flow turbine manifold. Refer to Section 3.21. The HIU will
require the flow rate to be set to obtain a temperature rise of
35
o
C at the tap furthest from the HIU.
3.
The HIU is suitable for connection to most types of washing
machine and dishwasher appliances.
4.
If the shower/mixer valve does not incorporate non-return
valves the following must be followed:
a.
The cold inlet to the HIU is fitted with an approved anti-
vacuum or syphon non-return valve.
b.
Hot and cold water supplies to the shower are of equal
pressure.
5. Hard Water Areas
Refer to Section 1.15 Water Treatment.
IMPORTANT.
Provision has been made to accommodate the
expansion of DHW contained within the unit by the use of a
fitted expansion mini vessel in the HIU on the outlet of the
DHW circuit.
Cold water, rising main and pipework in exposed areas need
to be suitably lagged to prevent freezing.
1.13 SYSTEM REQUIREMENTS
Water Flow Rate and Pressure Loss
Max CH Output
kW
5
Water flow rate
l/min
17.3
(gal/min) (3.8)
Temperature Differential
o
C 20
Head available for
m.w.g.
3.4
system
(ft.w.g.) (11.1)
Safety valve setting
bar
3.0
Vessel charge pressure
bar
0.5 to 0.75
System pre-charge pressure
bar
None
1.0
System volume
Expansion vessel
(litres)
volume (litres)
25
1.6 1.8
50
3.1 3.7
75
4.7 5.5
100
6.3 7.4
125
7.8 9.2
150
9.4 11.0
175
10.9 12.9
190
11.9 14.0
200
12.5 14.7
250
15.6 18.4
300
18.8 22.1
For other system volumes
multiply by the factor across
0.063 0.074
