10
IMAX XTRA EL
-
Installation & Servicing
GENERAL
4 SEALED SYSTEM REQUIREMENTS
Working pressure 6 bar maximum.
Particular reference should be made to BS. 6644 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.
In 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.
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 a 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
1.0 bar (15psi) and must take account of the 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 BSEN 61508.
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 0.35bar
(5psi) of the safety valve setting.
Other British Standards applicable to commercial sealed
systems are:
BS. 6880: Part 2
BS. 1212
BS. 6281: Part 1
BS. 6282: Part 1
BS. 6283: Part 4
3 VENTILATION
The ventilation requirements of these boilers are dependant
on the type of flue system used, and their heat input. All vents
must be permanent with no means of closing, and positioned to
avoid accidental obstructions by blocking or flooding.
Detailed reference should be made to BS. 6644 for inputs
between 70kW and 1.8MW (net). In IE refer to the current edition
of I.S.820. The following notes are for general guidance only:
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 25
o
C
within 100 mm of the floor, 32
o
C at mid height and 40
o
C within
100 mm of the ceiling.
IMPORTANT NOTE.
If combustion air is drawn from within the boiler room,
ensure no dust or airborne debris can be ingested into the
appliance. Dusty concrete flooring should be sealed to
reduce the presence of dust. Ideally where possible duct
the air supply into the boiler room from a clean source
outside the boiler room/building.
Open Flued Installations
If ventilation is to be provided by means of permanent high and
low vents communicating direct with outside air, then reference
can be made to the sizes below. For other ventilation options
refer to BS. 6644. In IE refer to the current edition of I.S.820.
Required area (cm
2
) per kW of total rated input (net)
Boiler Room
Enclosure
Low level (inlet)
4
10
High level (outlet)
2
5
Note: Where a boiler installation is to operate in summer months
(e.g. DHW) additional ventilation requirements are stated, if
operating for more than 50% of time (refer to BS6644).
IMPORTANT
;
If a sealed system is required please ensure a
maximum flow temperature of 90ºC is not exceeded.
