Potterton Housewarmer 45 Installation & Service Instructions Manual page 7

3. Installation Requirements – Page 7
To size the expansion vessel it is first necessary to calculate
the volume of water in the system in litres. The following
volumes may be used as a conservative guide to calculating
the system volume.
Boiler Heat Exchanger:
Small Bore Pipework:
Micro Bore Pipework:
Steel Panel Radiators:
Low Water Capacity Radiators:
Hot Water Cylinder:
If the system is extended, the expansion vessel volume may
have to be increased unless provision has been made for
extension. Where a vessel of the calculated size is not
available, the next available larger size should be used.
The boiler flow temperature is controlled at approximately
82°C.
The vessel size can now be determined from the information
in Table 1 where V = System volume in litres.
Vessel Charge Pressure (bar)
Initial System Pressure (bar)
Expansion Vessel Volume (litres)
Water Level
30.5
Metres
Max.
1.2
Metres
Min.
Heat
Exchanger
Central
Heating
Return
4 litres
1 litre per kW of system
output
7 litres
8 litres per kW of system
output
2 litres per kW of system
output
2 litres
0.5
1.0
V x 0.11 V x 0.087
Table 1.
Flow
Central
Heating
Return
Injector Tee
can be installed
in any direction
see Fig 14
Flow
Central
Heat
Exchanger
Heating
Cylinder
The hot water cylinder must be an indirect coil type or a
direct cylinder fitted with an immersion calorifier suitable for
operating at a gauge pressure of 0.3 bar (5 lbf/in
of safety valve setting. Single feed indirect cylinders are not
suitable for sealed systems.
Method of Make-up
Provision shall be made for replacing water loss from the
system either:
i) from a make-up vessel or tank mounted in a position
higher than the top point of the system, and connected
through a non-return valve to the system on the return
side of the hot water cylinder or the return side of all
heat emitters. or
ii) where access to a make-up vessel would be difficult by
using the mains top up method or a remote automatic
pressurisation and make-up unit as shown in
Figs. 7 & 8.
Mains Connection
There shall be no connection to the mains water supply or to
the water storage tank which supplies domestic hot water
even though a non-return valve, without the approval of the
Local Water Authority.
1.5 Filling Point
1.0 The system shall be fitted with a filling point at low level
which incorporates a stop valve to BS 1010 and a double
check valve (approved by the National Water Council) to be
fitted in this order from the system mains, see Fig. 7.
Flow
Central
Heat
Exchanger
Heating
Return
Flow
Heat
Exchanger
Return
Water Level
30.5M Max.
F ully
0.9M Min.
P umped
S ystem
Flow
Heat
Exchanger
Return
B B U Open V ented
S ystem V ariants
All Systems Illustrated
Can Be Fitted To The
Other Side Of the Boiler
On Combined Gravity
D.H.W. Pumped Heating
Systems The Injector
Tee Is To Be Fitted
Directly To The Boiler.
The Tee On The
Combined Flows Is
To Be Fitted As Close
To The Boiler As Possible
2
) in excess
Fig 3