Potterton PROFILE LPG 100e Installation And Servicing Instructions page 8

SITE REQUIREMENTS - Page 8
The System
The boiler must be used on INDIRECT hot water systems only.
It is suitable for use on open vented gravity domestic hot
water/pumped central heating systems or, fully pumped systems
which are open vented.
The system should be designed so that the maximum static
head does not exceed 30.5 m (l00ft) and a minimum on fully
pumped systems of 305 mm (1 ft). See FIG. 6.
Gravity domestic hot water circuits should have a minimum
circulating head of 1.2 m (4ft). See FIG. 8.
To ensure optimum boiler performance on both gravity hot water
and fully pumped systems a change-over switch is incorporated
in the boiler control box. The boiler is supplied with the switch
set for sealed or open vented fully pumped systems.
If the boiler is to be used on a system with gravity hot water the
switch should be set at the GRAVITY position. In addition the
bulb of the overheat thermostat should be repositioned as
shown in FIG. 21b.
To prevent reverse circulation in the gravity circuit when the
pump is running an injector disc is provided to form an injector
tee at the return connection on the boiler. See FIG. 20.
On all systems the pump should be wired to the boiler terminal
block. To prevent nuisance operation of the overheat
thermostat, it is important that where electrically operated zone
valves are used the boiler is wired so it does not cycle when the
zone valves are closed. Also, systems fitted with controls that
close both hot water and central heating circuits while the boiler
is still hot, must be fitted with a by-pass circuit to dissipate the
residual heat within the boiler.
Further information on by-pass arrangements is provided in later
notes and illustrations.
Drain off taps should be fitted in the pipework close to the boiler
and in the low points of the system.
Note: Although the system can be emptied using the drain off
taps installed in the pipework around the system, to empty the
boiler it is necessary to remove the drain off cap positioned
within the boiler case. See FIG. 2.
Combined Gravity Hot Water Pumped Central Heating
Systems. Where a cylinder thermostat and zone valve is used
to control the temperature of the hot water it is recommended
that a by-pass by installed in the gravity circuit. A suggested
method of doing this is shown in FIG. 8 where the bathroom
radiator is connected into the gravity circuit and is fitted with two
lockshield valves. Mechanically operated thermostatic domestic
hot water temperature control valves which allow the boiler to
operate when the valve is closed or partially closed MUST NOT
BE FITTED.
Fully pumped Systems
NOTE: Great care should be taken when selecting a pump to
ensure that the correct flow rate is achieved. Fully pumped
systems should be designed so that the system differential is no
greater than 15ºC.
With the change-over switch in the control box set at the FULLY
PUMPED position, the pump will be controlled by an over-run
thermostat. This will ensure that the pump will continue to run
after boiler shut down if the water temperature in the boiler is
high, thus preventing nuisance operation of the overheat
thermostat. If a three port diverter valve is used as shown in
FIG. 6; a bypass is
Supplied By www.heating spares.co Tel. 0161 620 6677
Not necessary since one circuit is always open.
Where a pair of two port valves are used, a by-pass is
necessary. The total length of the by-pass circuit taken from the
boiler connections should be greater than 4 metres of 22 mm
pipe. It should be fitted with a lockshield valve and be adjusted
to maintain a minimum flow through the boiler of 4.5 litres/mm (1
gal/mm) see Figs. 6, 7.
Systems fitted with controls which allow the boiler to operate
when both the hot water and central heating circuits are closed,
i.e. mechanically operated thermo-static control valves, must be
fitted with a by-pass circuit capable of:-
1. Dissipating a minimum of 1 kW (3400 Btu/h)
2. Maintaining a minimum water flow through the boiler of 9
litres/mm (2 gal/mm).
A suggested method of meeting these requirements by using a
bathroom radiator fitted with two lockshield valves is shown in
FIGS. 6, 7.
Additional system information can be found in the Control
Systems, Pipework and Wiring Guide.
SEALED SYSTEMS (FULLY PUMPED)
Installation
The installation must comply with the requirements of BS 6798
and BS 5449 Part 1. The B.G. publication "British Gas
Specification for Domestic Wet Central Heating Systems"
should also be consulted.
Safety Valve
A non adjustable spring-loaded safety valve, preset to operate
2
at 3 bar (45lbf/in ) shall be used. It must comply with BS 6759
Part 1 and include a manual 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 the safety valve. The valve
should 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 0-4 bar (60 lbf/in
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 15 mm (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 point 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:
2
) shall be fitted to the
6.5 litres
1 litre per kW of system output
Publication No. 559876/0296