gis

Hysteresis

The moment Tnet falls below (Tset - Tsolar diff - Hysteresis), the controller registers such a heat demand that the gas burner and the solar heating system jointly heat the water. The solar heating system is only employed when the temperature measured by S1 is a certain (adjustable) value grater than that of S2.

Tsolar diff

When Tnet exceeds (Tset - Tsolar diff), the gas burner is shut off and the water is heated exclusively by the solar heating system. When Tnet rises above Tset (provided Tset = Tsolar limit), the solar heating system switches off. The value of Tsolar diff is adjustable (12.9.5 "Setting the solar difference").

Tsolar limit

Preset (12.9.4 "Setting the solar limit temperature") water temperature at which heating via the solar heating system is stopped.

Graphical representation of heating cycle

Legend

A = Gas burner on

B = Gas burner offTsolar limit

Tnet:

= no heat demand, so water

not heated

= water heated via solar heating system

= water heated via solar heating system and gas burner

Tset

Solar diff.

t = time

T = Temperature

45 oC = Minimum tap water temperature

Hys.

Tmin = 45￿C

Note

Tnet can rise above Tset,. However, this is only possible if Tsolar limit is increased via the service menu.

Note

Tsolar limit can be lower than Tset; this will mean that Tnet can never be equal to Tset.

2.4Protection for the appliance

2.4.1Introduction

The electronic controller monitors the water temperature, helps ensure the safe use of the solar heating system, and ensures safe combustion. This takes place using:

the Appliance water temperature protection

the Gas valve

the Fan

the Pressure switch

the Flame probe

Instruction manual SGE

15

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Image 15
A.O. Smith SGE service manual Protection for the appliance Introduction, = Gas burner on = Gas burner offTsolar limit