Thermo Technologies SMT 100 - Manual (Page 11)

10
3.1.2 TEMPERATURE DISPLAY:
The display is used to show the corresponding information for each Display
Select Indicator.
3.1.3 TEMPERATURE SET INCREASE / DECREASE SWITCHES:
The keys are used to decrease or increase any of the system set
points. These keys have an auto repeat facility: press and hold in order to
advance quickly. Please note that the unit must be in programming mode
before any set points can be adjusted.
3.1.4 DISPLAY SELECTOR SWITCH:
Pressing the key will advance the display selector lamp to the next option.
This allows you to view a system temperature or set point depending on the
mode of the unit.
3.2 PRINCIPLE OF OPERATION
3.2.1 PUMP OPERATION:
In the simplest form the solar system needs two sensors. One is positioned
at the collector (manifold) usually on the roof, which is called the Collector
Sensor . The second is positioned such that it measures the temperature
of the water returning to the collector, after the system has extracted the heat
from it. This is called the Return Sensor .
Two conditions must be satisfied before the pump will run:
1 As the sun shines on the collector, the collector sensor picks up the rise
in temperature, while the return sensor remains at the existing
temperature. The difference between these two temperatures is referred to
as Delta T ( ). For example, when is set to 4, the collector temperature
must rise at least 4°C above the return temperature before the pump
will operate, but only when condition 2 is also satisfied.
2 The collector temperature must be above the minimum collector
temperature set point TC (for example 40°C), before the pump will operate to
optimise the use of the solar collector.
3.2.2 AUXILIARY OPERATION:
In the normal mode of operation, the SMT 100 provides the facility, which
allows the solar controller to either operate an auxiliary heater for boosting
the temperature, or to divert surplus heat to another circuit. This function is
totally independent in its operation to the solar pump control described above,
and has its own separate sensor , and an output relay marked “AUX.”.
The thermostat set point is called TT.
When temperature is below TT set point, C is connected to contact 1.
When temperature rises above TT set point, C is connected to contact 2.