Sealed Systems
A sealed system should follow the guidelines given
in the Code of Practice BS 7074 :1. It should
include a safety valve to BS 6750 Pt 1. fitted close
to the boiler, without an intermediate valve to the
system and in a position where it can be tested. It
should be preset to operate at 3 bar (45 lb/in²) and
sited to discharge through a pipe to a safe outlet.
An expansion vessel complying with BS 4814 must
be fitted to the system close to the return side of the
pump. The connection should be not less than
15mm and without a valve or restriction. Size the
vessel by using the table below.
1. Choose a vessel pressure by taking the static
head of the system, adding 0.3 bar, and taking
the nearest larger size.
2. Select the Vessel Volume from the table below
by finding the system volume and vessel pres-
sure.
3. Choose that size or larger from the
manufacturers’ range.
Vessel
System Volume
Litres
Pressure
50
60
70
100
150
Bar
Vessel Volume
0.5
4
4
8
8
12
1.0
8
8
8
12
18
1.5
8
12
12
18
24
A pressure gauge with a fill pressure indicator and a
range of 0-4 bar should be fitted close to the expan-
sion vessel in a visible position.
A design as detailed below should be used for the
filling connection, it utilises a BS 1010 stop valve, a
double non-return valve and filling loop fitted at low
level and should be installed with the approval of the
local Water Undertaking.
Electricity Supply
Refer to Figs. 3 and 4.
Wiring external to the appliance MUST be in accord-
ance with the current I.E.E. Wiring Regulations and
any Local Regulations that apply.
The boiler is supplied for 230V ~ 50Hz. Single
phase. Fuse rating is 3A.
The method of connection to the mains electricity
supply MUST facilitate complete electrical isolation
of the boiler, preferably by the use of a fused double
pole switch having a 3mm (1/8in.) contact separa-
tion in both poles and servicing only the boiler and
system controls.
The point of connection to the mains should be
readily accessible and adjacent to the boiler, except
that, for bathroom installations, the point of connec-
tion to the mains MUST be situated outside the
bathroom.
Note.
Where a room sealed appliance is installed in
a room containing a bath or shower, the appliance,
any electrical switch or appliance control utilising
mains electricity should be so situated that it cannot
be touched by a person using the bath or shower.
Installation Of Boiler
Suggested procedure:
1. Site to suit system and terminal limitations.
2. Mark Boiler Mounting Box fixing position. (Fig.
5).
3. Mark & Drill Flue hole(s).
(see Fig. 7 for Concentric, Fig. 8 for Twin Pipe).
4. Fix Boiler Mounting Box to the wall.
5. Remove the Electrical tray and the Case from
boiler module.
6. Plumb module for water and gas OFF the wall
(access is much better).
7. Fix the Boiler to its Mounting Box.
8. Plumb tails to system and gas.
9. Test for leaks.
10. Replace the Case and Electrical tray.
Space Required for Installation and Service.
Right or Left
30 mm
1¼ in.
Above
30mm
1¼ in.
Below
25mm
1 in.
In Front
450mm
18 in.
Condensing Boiler
5
03/09/02
ALTERNATIVE METHODS OF FILLING A SEALED
SYSTEM
Method A
Method B
Hose Unions
Air Inlet
Valve
Temporary Hose
Mains
Water
Supply
Mains
Water
Supply
Test Cock
Stop Valve
Drain &
Fill
Double
Check
Valve
Assembly
Drain &
Fill
Cistern &
Overflow
Pressure
Pump &
Reducing
Valve If
Required
Stop Valve
