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Page 15
GULFSTREAM
A-CL
ASS
3.3.2 Sealed central heating system
(a) Sealed System SS models: These are
suitable for sealed central heating systems
shown schematically in figure 3.2 and are
fitted with an automatic arrangement.
Minimum of 2 bar mains pressure must
always be available for correct operation
of the CA device (figure 3.3) These models
incorporate the following additional
components:-
• 16 litre expansion vessel precharged to 1.0
bar.
• 0-4 bar pressure guage
• Expansion relief valve - set to operate at 3.0
bar
• Automatic filling assembly incorporating
CA type backflow prevention valve.
• Store overheat thermostat.
(b) CA automatic filling device: The automatic system filling arrangement
incorporating CA type backflow prevention valve and pressure regulator replaces
the normal system filling loop used with sealed heating systems and this will
allow any loss of water from the heating system to be automatically replenished
as with an open vented system fitted with a feed and expansion cistern.
CA automatic filling device and pressure regulating valve is set to fill the system
to 1.0 bar. This is usually sufficient for the heating systems in most domestic
properties. However the minimum system pressure should not be less than “0.5
+ H/10” bar as shown in figure 3.2. The system filling pressure can be adjusted
by the pressure regulator (see figure 3.3)
Note: If the system pressure is adjusted, then the expansion vessel charge pressure
should be adjusted and the expansion vessel size must also be recalculated.
(c) Expansion vessel: The expansion vessel must accommodate the change in
volume of system water heated from 10
o
C to 110
o
C (see BS 5449:1990 clause
16.2). When calculating the system water content, the capacity of the hot water
store (100 litres) must be included. The expansion vessel requirement are shown
in table 3.2
Note: After first filling the system to a pressure of 1.0 bar at mains supply temperature
(typically 15
o
C in summer), the system (space heating and hot water) should be
heated to its maximum temperature. If the pressure guage indicates 2.6 bar or higher,
then an additional expansion vessel may be required. Expansion vessel requirements
are shown in table 3.2
(d) Discharge pipe: The discharge pipes from the system pressure relief valve and
the CA valve are terminated into 2 individual tundish arrangements inside the
appliance. These are combined to run in a 22mm minimum diameter discharge
pipe which must have a continuous fall throughout its length. The discharge pipe
details are shown in table 3.3 and figure 3.4
The discharge pipe should be terminated in a way that it permits safe discharge
of hot water such that no hazard to persons or damage to property or electrical
components is caused.
Figure 3.2 Schematic diagram of the sealed heating system
SYSTEM DESIGN
GulfStream
A-CLASS
SS models
Minimum System Pressure = H/10 + 0.5 bar
Maximum System Pressure = 2.5 bar
H (meters)
Figure 3.2 Schematic Diagram of the Sealed Heating System
Isolating valve
Y -Line
strainer
Isolating valve
CA Valve
Tundish
Figure 3.3 CA Filling Device
Pressure
regulator
Le
Tundish
Discharge from CA - Valve
h
Discharge
from PRV
Figure 3.4 Tundish discharge pipe requirements
Figure 3.3 CA Filling device
Summary of Contents for GS A-Class 12/OV
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