A.O. Smith SGS-28, Инструкция по установке, эксплуатации и обслуживанию

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5.4 Operating cycle
The water temperature (T
1
) at the top of the water heater is used to control 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
1
and S
2
). T
1
is the curve shown in
the figure. The controller uses two measured values to calculate this temperature: T
1
(7)
and T
2
(13). In addition, temperatures S
1
, S
2
and S
3
are used by the solar heating system
controller. S
1
is measured in the solar collector. S
2
is located between the inlet and outlet
of the heat exchanger of the storage tank. S
3
is measured at the top of the storage 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
3
is 5 °C higher than T
top
(T
1
).
Water is then pumped from the water heater to the storage tank, causing hot water to
flow from the storage tank into the water heater. The pump switches off as soon as S
3
is
equal to T
1
.
The other settings that govern the control behaviour are:
T
set
T
set
is the the required water temperature that has been set on the appliance (see
section 4.3.3.1). As soon as T
1
falls below T
set
, the solar heating system starts
heating the water, but only if the temperature of the heating fluid (S
1
) is greater
than the temperature measured at the appliance (sensor S
2
) by a given (adjustable)
amount. When T
1
= T
set
= T
solar limit
, heating by the solar heating system stops.
There is one exception to this rule, which is when T
solar limit
is set to a higher value
than T
set
.
Hysteresis
The moment that T
1
falls below (T
set
- T
solar 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 S
1
is a certain (adjustable) value grater than that of S
2
.
T
solar diff
When T
net
exceeds (T
set
- T
solar diff
), the gas burner is shut off and the water is
heated by the solar heating system alone. When T
1
rises above T
set
(provided that
T
set
= T
solar limit
), the solar heating system is switched off. The value of T
solar diff
is
adjustable (see section 9.2.8.4).
T
solar limit
Preset water temperature at which heating via the solar heating system is stopped
(see section 9.2.8.3).
Fig. Graphical representation of operating cycle
T
solar limit
T
set
Solar diff.
Hys.
T
min = 45°C
A.
Gas burner on
B.
Gas burner off
T1.
No heat demand, so water is not
heated
Water heated via solar heating system
Water heated via solar heating system
and gas burner
t.
time
T.
Temperature
45°C = Minimum tap water
temperature
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0311753_SGS_28-120_II_UKUK_V2.0 , 2017-05-03 45