A.O. Smith SGE, Installation And Operation Manual

Page: 13 / 110

Instruction manual SGE 13
gis
2 Working principle of
the appliance
2.1 Introduction Topics covered in this chapter:
•
General working principle of the appliance ;
• The appliance's heating cycle ;
• Protection for the appliance ;
• Safety of the installation ;
• Protection for the solar heating system .
2.2 General working
principle of the
appliance
The figure shows a cut-away view of the appliance.
In this appliance, the cold water enters the bottom of the tank through the cold
water inlet (14). The water is heated by means of a heat exchanger (55)
connected to a solar heating system
(2.6 "Protection for the solar heating
system") and a gas-fired heat exchanger (11). The air required by the latter for
combustion is forced into the burner (17) by the fan (18).
The heated tap water leaves the tank through the hot water outlet (2). Once the
appliance is completely filled with water, it will constantly be under mains water
pressure. As hot water is drawn from the appliance, cold water is immediately
added.
The gas is fed to the burner via the gas control (16). The modulated supply of
gas and air ensures that the optimum gas/air mixture is always achieved. The
special construction of the burner causes the mixture to form a vortex (cyclone
effect) before it becomes ignited. This vorticity improves the ignition on the hot
surface igniter (20), as well as ensuring optimum combustion efficiency. The
special design of the heat exchanger (11) ensures that the flue gases are first
led downwards via the combustion chamber, then upwards via the heat
exchanger, and downwards again alongside the water in the tank. The flue
gases gradually become cooler in the process. Because the cooled flue gases
flow alongside the cold water lower down in the tank, they start to condense.
This condensation causes latent heat energy to be transferred to the cooler
water, thereby increasing the performance of the unit. The condensate yielded
by this process is discharged via the siphon (23).
The insulation layer (24) prevents heat loss. The inside of the tank is enamelled
to protect against corrosion. The anodes (9) provide extra protection against
corrosion.
The appliance has an inspection and cleaning opening (12) for maintenance.