andrews 24/39, Installation And Service Manual

Page: 23 / 116

Issue 2 14/07/16 23
Installation 3
Note
Both air vents must communicate with the same room or
internal space or must both be on the same wall to
outside air.
1. The effective area requirements specified in the table
are related to the maximum net input of the heater(s)
and are equivalent to those specified in BS 6644 and
IGE/UP/10 Pt.1.
2. The free area of the grilles should not be less than the
size of the recommended ventilation opening.
3. The supply of air to a space housing the heater(s) by
mechanical means should be: (a) Mechanical inlet
with natural extraction. (b) Mechanical inlet with
mechanical extraction.
Natural inlet with mechanical extraction must not be
used.
Where a mechanical inlet and mechanical extraction
system is used, the design extraction rate must not
exceed one third of the design inlet rate.
All mechanical ventilation systems must be fitted with
automatic gas shut off safety systems which cut off the
supply of gas to the heater(s) in the event of failure of
either the inlet or extract fans.
The requirements for air supply by mechanical ventilation
are given in BS 6644 Clause 19.3. and IGE/UP/10 Pt.1.
The permanent air vents shall be sited away from any
extract fans. Where an extract fan is fitted, check for
spillage at the draught diverter as detailed in BS 5440
Part 1 Appendix B. It may be necessary to increase the
ventilation area to compensate for the extract fan.
4. The vapours emitted by halogen based compounds
can, if drawn into the combustion air, cause corrosion
of the gas burner, thermocouple and storage vessel.
Therefore, if heaters are to be installed in locations
where halogens are likely to be present, they should
be isolated from such compounds and ventilated from
and to outside uncontaminated atmosphere.
Some of the vulnerable areas are:
(a) Hairdressing salons and adjoining rooms and
basements
(b) Establishments where dry cleaning solutions are used
or stored.
(c) Degreasing plants using hydrocarbon solvents.
(d) Premises where refrigerant gases are used or stored.
The minimum effective areas of the permanent air vents
required in the compartment are as follows;- .
Air Vent Areas
Position of Air Vents Air from room or internal space Air direct from outside
High Level 10cm
2
per kW net 5cm
2
per kW net
Low Level 20cm
2
per kW net 10cm
2
per kW net