Baxi Bermuda 45/4 M Installation And Servicing Instructions page 7

SYSTEM DETAILS - Page 7
System Controls
For optimum operating conditions, the heating system into
which the appliance is installed should include a control
system.
Such a system would comprise a timer control and a
separate room and/or cylinder thermostat as appropriate.
The boiler should be controlled so that it operates on
demand only.
It is not economical to rely on the boiler thermostat to
control operation of the system.
Fully Pumped System
The sizes of the system pipes should be determined by
normal methods (BS 5449).
The open vent pipe should be a minimum of 22mm and must
rise continuously to a point above the feed and expansion
tank.
The flow pipe from the boiler may form part of the vent pipe.
No part of the open vent should contain a valve.
The cold feed pipe (15mm mm) should preferably be
connected to the boiler return.
Close coupling of the cold feed pipe to the flow pipe at a
maximum of 150mm (6 in) from the vent pipe is permissible
but there must always be an open cold water path to the
boiler return connection.