Thermo Products USDT2004 - Manual (Page 2)

2
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.
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 (T
3
, 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 (-3
o
F to 41
o
F) frost protection
•
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 (T
1
, at S
1
) and the return temperature (T
2
, at S
2
,
bottom of the storage tank). The solar loop circulation pump runs while the collector temperature
exceeds the return temperature by an adjustable
temperature difference diff. To avoid overheating, the
circulation pump stops if the return temperature (T
2
)
reaches the adjustable high limit (T
MAX
) temperature. The
temperature hysteresis (a lagging in the set -point) may
over-ride diff to avoid pump cycling.
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 T
MAX
:
A1 (ON) only when S1 > (S2 + diff) & S2 < T max
U
S1
S2
A1