andrews L24/31, Installation Manual, Operation And Service Manual

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AIR SUPPLY
AND
VENTILATION
WATER QUALITY
AND
TREATMENT
INSTALLATION SECTION 3
14
IMPORTANT!
1. The effective area requirements specified in the table are related to the net heat input of
the heater(s) and are equivalent to those specified in BS 6644 and IGE/UP10 Pt1.
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.
NOTE! 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 Pt1.
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.
Where extreme conditions of water hardness exist, scale can form in any water heating
equipment, especially when the heater is working under conditions of constant heavy
demand and at high temperatures.
Each water heater is fitted with one or more magnesium anode(s) which protect the tank
from corrosion caused by electrolytic action. Magnesium anodes are sacrificial in that they
corrode as they protect. When the anode has eroded to less than 50% of it's original
diameter, it may not offer protection.The anodes should be inspected annually and replaced
as necessary. Frequency of anode replacement will vary dependent on water quality.
Andrews Water Heaters offer Correx TM UP powered anodes as an alternative to the standard
magnesium anodes. These anodes do not need maintenance or replacement. The
potentiostat which regulates the current to the Correx
TM anode, features an indicator light
which shows green to indicate correct function and red to indicate malfunction. These
anodes are available as an optional extra on all Andrews heaters.
In hard water areas, scale formation can occur in hot water systems and hot water heaters
and the higher the temperature and volume of water used, the more problematic the scale
build-up can be. Water treatment is normally recommended when the hardness reaches
100 - 150ppm (7 - 10 degrees Clark) and above. This problem can be minimised by
reducing the water temperature in the heater and by fitting suitable water pre-treatment
equipment.
When installing Andrews Water Heaters in hard water areas we would recommend
that a water treatment specialist is consulted.