10
Henrad SEC FF -
Installation
4
SYSTEM REQUIREMENTS - Central Heating
GENERAL
Notes
a.
The method of filling, refilling, topping up or flushing
sealed primary hot water 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 boilers having aluminium heat
exchangers may be used in the central heating system.
Advice should be sought from a local water treatment
company.
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 82
0
C.
3.
All components of the system must be suitable for a
working pressure of 3 bar and temperature of 110
0
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 pre-set lift pressure
of 3 bar.
c.
Pressure gauge, covering a range of 0 to 6 bar.
d.
A 9-litre expansion vessel, with an initial charge
pressure of 0.75 bar.
4. 'Make-up' Water.
Provision must be made for replacing
water loss from the system, either :
a.
From a manually filled 'make-up' vessel with a readily
visible water level. The vessel should be mounted at
least 150mm above the highest point of the system
and be connected through a non-return valve to the
system, fitted at least 150mm below the 'make-up'
vessel on the return side of the radiators.
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
or
b.
Where access to a 'make-up' vessel would be
difficult, by pre-pressurisation of the system.
The maximum cold water capacity of the system
should not exceed 143 litres, if not pressurized.
However, if the system is to be pressurized, the
efficiency of the expansion vessel will be
reduced and a larger vessel (or smaller system
volume) may be necessary. If the capacity of the
vessel is not considered sufficient for this, or for
any other reason, an additional vessel MUST be
installed on the return to the boiler.
Guidance on vessel sizing is given above.
Water Flow Rate and Pressure Loss
Boiler size
24
System Load
24 kW
Water Flow Rate
0.51 l/s
Temperature Differential
11
o
C
Pressure available
29 kPa
for system
2.9 m
