Sirius FS
18
GB/IE
4.5 HYDRAULIC PUMP REQUIREMENTS
The size of the pumps must be determined by the installer or technical engineer
according to boiler data and system design (see notes below). If using the boiler
with a secondary heat exchanger, it is important to size the pumps on the secondary
side correctly, so that the correct
r
T can be achieved on the primary side.
The installer
must ensure that when the boiler demand is turned on, the boiler
circulation pump and where applicable, the secondary system circulation pump must
be active at the same time. When the boiler demand is switched off the circulation
pump and where applicable, the secondary system circulation pump must continue to
run on for a minimum of three minutes after boiler operation has stopped. Failure to
ensure minimum water circulation when the burners of the boiler are in operation
may result in premature heat exchanger failure.
A system which proves the operation (by means of water flow or motor current) of
the boiler circulation pumps, before the burners of the boiler can operate is
recommended to ensure long service life
The use of a mixing header fitted between the boiler circuit and system circuit is
recommended. This becomes essential if the system requires flow rates superior
to the maximum permitted boiler flow rates, (i.e. less than
r
T 20
0
C)
4.5.1 Minimum Flow Requirements
The boiler pump must have a delivery head which can ensure the following minimum water
flow rates at all times (equivalent to a
r
T of 35
0
C at maximum output) :
With the boiler firing at maximum rate the
r
T should not be less than 20
0
C (unless using a
mixing header system)
Model
Minimum
Water flow
rate (m
3
/h)
FS400
6.75
FS525
9.00
