HAMWORTHY HEATING LTD
MILBORNE 500 SERIES
500001130/A
10
Safety valve
Each 50kW boiler module is supplied with a fitted
safety valve rated at 6 barg. This ¾” valve is piped
to the bottom of the boiler module where it must be
piped to discharge via a tundish (not supplied). The
discharge should be in an obvious position to alert
the responsible person of a problem.
System Pump Size
The pump is not an integral part of the boiler.
Consequently, its size should be chosen considering
the features of the Boiler assembly and of the
system to be fed.
To help choose the correct pump, figure 7.5 shows
the curve of flow resistance values inside the boiler.
Pump Type
Pumps should be of the electronic constant
pressure type. This will ensure that as boiler
modules are turned off and the individual motorised
isolating valves close, flow rates for the remaining
modules are maintained.
Alternatively a fixed speed pump with flat curve
characteristics may be used.
Maximum Operating Pressure
The boiler’s maximum operating pressure is 6 bar,
its minimum operating pressure is 0.5 bar.
Boiler Filling and Draining
The boiler should be filled using the system quick fill
connection. This connection must be removed after
filling.
The boiler should be drained using the relevant
drain valves fitted to the boiler or system.
Flow rate requirements
As a condensing boiler the Milborne is designed for
operation at 20°C differential temperatures. Should
the flow rate drop the boiler will recognise the
change in differential temperature and modulate the
burner to maintain 20°C differential. It is therefore
important to size the pumps based on a flow rate of
0.6 l/sec (2160 l/hr) per 50kW boiler module plus an
allowance for system resistance.
MILBORNE 501
Figure 7.5 - Flow Resistance Graph
