Advertisement
TECHNICAL DATA - Page 10
testing device. It shall be positioned in the flow pipe either
horizontally or vertically upwards and close to the boiler. No
shut-off valves are to be placed between the boiler and
safety valve. The valve shall be installed into a discharge
pipe which permits the safe discharge of steam and hot
water such that no hazard to persons or damage to electrical
components is caused.
Pressure Gauge
A pressure gauge incorporating a fill pressure indicator,
covering the range 1-4bar (60lbf/in2) shall be fitted to the
system. It should be connected to the system, preferably at
the same point as the expansion vessel. Its location should
be visible from the filling point.
Expansion Vessel
A diaphragm-type expansion vessel to BS4814 Part 1 shall
be fitted close to the inlet side of the pump. The connecting
pipework should not be less than 15mm (½ in nominal).
Pipework connecting the expansion vessel should not
incorporate valves of any sort. Methods of supporting the
vessel are supplied by the manufacturer. The nitrogen or air
charge pressure of the expansion vessel shall not be less
than the hydrostatic head, (height of the top of the system
above the expansion vessel). 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 may have to
be increased unless previous provision has been made for
the extension. Where a vessel of the calculated size is not
available, the next available larger size should be used.
6.5 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
The boiler flow temperature is controlled at approximately
82°C.
The vessel size can now be determined from the following
table where V = System volume in litres.
Vessel Charge
0.5
Pressure (bar)
Initial System
Pressure (bar)
0.5
Expansion Vessel
Volume (litres)
V x 0.833
This is a general guide; if it is required to be more accurate
refer to BS7074.
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 pressure of 0.3bar (5lbf/in2) in excess 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 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 illustrated in Fig 6
METHODS 1 & 2.
Mains Connection
There shall be no connection to the mains water supply or to
the water storage tank which supplies domestic water even
through a non-return valve, without the approval of the local
Water Authority.
Filling Point
The system shall be fitted with a filling point at low level
which incorporates a stop valve to BS1010 and a double
check valve (approved by the National Water Council) to be
fitted in this order from the system mains. Refer to Fig 6
METHOD 1.
10
.0
1.0
V x 0.11
Hide quick links:
Advertisement
