10
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Installation & Servicing
GENERAL
Working pressure 6.0 bar maximum, 0.8 bar minimum.
There is no minimum water pressure switch on the boiler, with
safety thermostats providing protection against dry firing.
However, should a minimum water pressure switch be
required in the system a ¼” connection is available on the
return manifold. The electrical connections should be made in
series with the minimum gas pressure switch.
Particular reference should be made to BS. 6644: Section 2;
Subsection 11 and Guidance note PM5 "Automatically
controlled steam and hot water boilers" published by the
Health and Safety Executive.
The information and guidance given below is not intended to
override any requirements of either of the above publications
or the requirements of the local authority, gas or water
undertakings.
In general commercial closed pressurised systems are
provided with either manual or automatic water make up.
On both instances it will be necessary to fit automatic controls
intended to protect the boiler, circulating system and ancillary
equipment by shutting down the boiler plant if a potentially
hazardous situation should arise.
4
SEALED SYSTEM REQUIREMENTS
Examples of such situations are low water level and operating
pressure or excessive pressure within the system. Depending
on circumstances, controls will need to be either manual or
automatic reset. In the event of shutdown both visual and
audible alarms may be necessary.
Expansion vessels used must comply with BS. 4814 and must
be sized on the basis of the total system volume and initial
charge pressure.
Initial minimum charge pressure should not be less than 0.8
bar (11.6 psi) and must take account of static head and
specification of the pressurising equipment. The maximum
water temperatures permissible at the point of minimum
pressure in the system are specified in Guidance Note PM5.
When make-up water is not provided automatically it will be
necessary to fit controls which shut down the plant in the event
of the maximum system pressure approaching to within 0.35
bar (5 psi) of safety valve setting.
5
VENTILATION
Detail reference should be made to BS.6644:1991. The
following notes are for general guidance only:
If ventilation is to be provided by means of permanent high and
low vents communicating directly with outside air, then
reference can be made to the sizes below. For other
ventilation options refer to BS. 6644.1991.
Dust contamination in the combustion air may cause blockage
of the burner slots. Unless the boiler room provides a dust
free environment then direct connection of the air intake via
ducting to clean outside air should be used.
The temperature within a boiler room shall not exceed
25ºC within 100mm of the floor, 32ºC at mid height and
40ºC within 100 mm of the ceiling.
Total input
Position of air
Air vent areas (air
rating of boiler
vents
direct from outside)
HIGH LEVEL
270 cm
2
plus
2.25 cm
2
per kW
Up to 2MW
in excess of 60 kW
total rated input
LOW LEVEL
540 cm
2
plus
4.5 cm
2
per kW
in excess of 60 kW
total rated input