Water Heater Operating Cycle - A.O. Smith SGS-28 Installation, User And Service Manual

gis
2.3 Water heater
operating cycle
Instruction manual SGS
The water temperature (T
1
when the gas burner is started and stopped. The temperature changes in the
water heater are used for switching the solar heating system on and off (using
T and S ). T is the curve shown in the figure. The controller uses two
1 2 1
measured values to calculate this temperature: T
temperatures S , S and S
1 2 2
is measured in the solar collector. S
the heat exchanger of the storage tank. S
tank.
Depending on whether or not hot water is being drawn off, hot water can be
pumped from the storage tank to the water heater. This happens if S
higher than T (T ). Water is then pumped from the water heater to the storage
top 1
tank, causing hot water to flow from the storage tank into the water heater. The
pump switches off as soon as S
The other settings that govern the control behaviour are:
• T
set
T is the the required water temperature that has been set on the
set
appliance (11.4.1 "Setting the water temperature via the SET POINT
MENU"). As soon as T
1
heating the water, but only if the temperature of the heating fluid (S
greater than the temperature measured at the appliance (sensor S
given (adjustable) amount. When T
heating system stops. There is one exception to this rule, which is when
T is set to a higher value than T
solar limit
• Hysteresis
The moment that T falls below (T
1
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 S
than that of S .
2
• T
solar diff
When T exceeds (T
net set
is heated by the solar heating system alone. When T
(provided that T = T
set solar limit
value of T is adjustable (12.9.4 "Setting the solar difference").
solar diff
• T
solar limit
Preset (12.9.3 "Setting the solar limit") water temperature at which heating
via the solar heating system is stopped.
) at the top of the water heater is used to control
(7) and T
1
are used by the solar heating system controller. S
is located between the inlet and outlet of
2
is measured at the top of the storage
3
is equal to T .
3 1
falls below T , the solar heating system starts
set
= T = T
1 set solar limit
.
set
- T - hysteresis), the controller
set solar diff
is a certain (adjustable) value grater
1
- T ), the gas burner is shut off and the water
solar diff
), the solar heating system is switched off. The
(13). In addition,
2
1
o
is 5 C
3
) is
1
) by a
2
, heating by the solar
rises above T
1 set
15