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 2004 is a powerful temperature differential control unit. It has *two programs and may be used in a wide range of applications:
PROGRAM 0 – This program is USDT 2004's basic program. Set at the factory, it uses two sensors to control a simple solar water heating system.
PROGRAM 1- This program allows the user to customize USDT 2004 for applications where a third sensor is required. With this program you may, for example, measure the flow rate or the temperature of the storage tank (T3, top of the tank).
*USDT 2004 has additional programs available for a wide variety of advanced applications, these programs are not supported at this time.
The control unit has the following functions:
∙2 inputs for temperature sensors (PROGRAM 0)
∙1 input for flow rate measurement or additional temperature sensor (PROGRAM 1)
∙BTU meter capability for constant flow rate or with a flow meter
∙Adjustable hysteresises dependant on temperature
∙Adjustable
∙Adjustable (200 o F to 299 o F) overheating protection
∙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
Program 0 – Two Sensor Operation (Factory Setting)
Program 0 monitors the collector temperature (T1, at S1) and the return temperature (T2, at S2 , bottom of the storage tank). The solar loop circulation pump runs while the collector temperature
exceeds the return temperature by an adjustable | S1 |
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temperature difference diff. To avoid overheating, the |
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circulation pump stops if the return temperature (T2) |
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reaches the adjustable high limit (TMAX) temperature. The |
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temperature hysteresis (a lagging in the set |
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The pump A1 runs only when the temperature at the |
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collector sensor location S1 is higher than the return |
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temperature at location S2 by at least diff (?T). The pump |
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stops if diff is less than the preset value or, when the |
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temperature at location S2 has reached the TMAX : |
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A1 (ON) only when S1 > (S2 + diff) & S2 < T max
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