O Potterson CF 20/35, Installation And Servicing Instrucnions

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wn in FIG. 6 where the bathroom radiator is connected into the gravity circuit a
nd is fitted with two lockshield valves.
Fully Pumped Systems
The pump must always be wired directly to the boiler terminal block as shown
in
FIG. 12 .
If a three port diverter valve is used as shown in FIG. 4 . a by-
pass is 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
of22 mm pipe. It should be fitted with a lockshield valve and adjusted to maint
ain a minimum flow through the boiler of 4.5 litres/mm (1 gal/min). Alternativel
y, the by-
pass canbe provided using the bathroom radiator as shown in FIGS.
4 & 5 .
Systems fitted with controls which allow the boiler to operate when both the ho
t water circuit and the central heating circuits are closed i.e. mechanically oper
atedthermostatic control valves, must be fitted with a bypass circuit capable of
:-
1 Dissipating a minimum of 1 kW (3400 Btu/h).
2. Maintaining a water flow through the boiler of 9 litres/mm (2 gal/min).
A suggested method of meeting these requirements by using the bathroom ra
diator fitted with two lockshield valves is shown in FIGS.
4 & 5 .
SEALED SYSTEMS
Installation
The installation must comply with the requirements of BS. 6798 1987 and BS.
5449 Part 1. The B.G. Publication "British Gas Specification for Domestic Wet
CentralHeating Systems" should also be consulted.
Safety Valve
A non adjustable spring-loaded safety valve pre-
set to operate at 3 bar (45
lbf/in²) shall be used. It must comply with BS. 6759
Part 1 and include a manual testing device. Itshall be positioned in the flow pip
e 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 s
team and hot water such that no hazard to persons or damage to electricalco
mponents is caused.