O Potterson CF 20/35, Installation And Servicing Instrucnions

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TECHNICAL DATA - Page 9
THE SYSTEM
The boiler must be used on Indirect hot water systems only. It is suitable for u
se on sealed or open vented gravity domestic hot water/pumped central heati
ng systems or fullypumped systems.
The system should be designed so that the maximum static head does not ex
ceed 30.5m (100 ft) and a minimum on fully pumped systems of 305mm (1 ft.)
. See
FIG. 4 .
If a minimum 305 mm (1 ft) head is used extra care should be taken when des
igning the system to ensure that pumping over or sucking down at the vent pip
e cannot occur.
Gravity domestic hot water circuits should have a minimum circulating head of
1.2 m (4 ft). SEE
FIG. 6 . To prevent reverse circulation in the gravity circuit w
hen the pump isrunning, an injector tee is provided. This must be installed as
shown in
FIG 10a .
To prevent nuisance operation of the overheat thermostat, it is important that
where electrically operated zone valves are used the boiler is wired so that it d
oes not cyclewhen the zone valves are closed. Also systems fitted with control
s that close both hot water and central heating circuits while the boiler is still h
ot must be fitted with a by-
passcircuit 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 if it is in a low point
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 n
ecessary to remove the drain-
off plug in thefront lower left of the casting. SEE
FIG. 2 .
Combined Gravity Hot Water and Pumped Central Heating systems.
Where a cylinder thermostat and zone valve are fitted to control the temperatu
re of the domestic hot water it is recommended that a by-
pass be installed in the gravity circuit.A suggested method of doing this is sho