Introduction
Note: The information supplied in this manual is for guidance only - no part of this may be used for any agreement, whether express or implied, or to form any contract. Thermo Technologies reserves the right to change specifications without prior notice.
U SDT 2004B is a powerful temperature differential control unit. It uses two temperature sensors to control a simple solar water heating system; one sensor measures the temperature of the solar collector whilst the second sensor measures the temperature at the
bottom of the tank.
The control unit has the following basic functions:
∙2 inputs for temperature sensors
∙Hi/Low adjustable
∙Adjustable (4.1 o F to 99 o F) temperature difference ?T
∙Manual override of pump for system testing
∙Digital display of all parameters
∙System status and diagnostic displays
Operation
The controller uses two sensors. One sensor (S1 in diagram) monitors the collector temperature whilst the other sensor (S2) monitors the temperature at the bottom of the storage tank. The solar
loop circulation pump runs while the collector temperature | S1 |
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exceeds the tank temperature by an adjustable temperature |
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difference diff. To avoid overheating, the circulation pump |
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stops if the tank temperature reaches the adjustable high |
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limit (TMAX) temperature. |
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The pump A1 runs only when the temperature at the collector sensor location S1 is higher than the return temperature at location S2 by at least diff (?T). The pump stops if diff is less than the preset value or, when the temperature at location S2 has reached the TMAX :
A1 S2
A1 (ON) only when S1 > (S2 + diff) & S2 < T max
2
