Thermo Products USDT 2004B - 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 and may be used in a wide
range of applications. The user has the choice of *two modes:
Par Mode (access code 32) – This program is USDT 2004's basic program. It uses two sensors
to control a simple solar water heating system and factory settings may be altered.
Men Mode (access code 64) - This program, initiated by the user, customizes USDT 2004 for
applications involving a BTU Meter or where a third sensor (or reference value) is required.
*NOTE: USDT 2004 may be used for several advanced applications originating in Men Mode.
USDT 2004 has the following functions:
•
2 inputs for temperature sensors
•
Input for flow rate input or additional temperature sensor
•
BTU meter capability for constant flow rate or with a puls flow meter
•
Adjustable (-4
o
F to 39
o
F) frost protection
•
Adjustable (32
o
F to 299
o
F) overheating protection
•
Adjustable (1
o
F to 99
o
F) temperature difference ?T
•
Manual pump operation
•
Digital display of all parameters
•
System status and diagnostic displays
Two - Sensor Operation
At its most basic function, USDT 2004 is a two-sensor
solar hot water controller. 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 exceeds the tank temperature
by an adjustable temperature difference diff. To avoid
overheating, the circulation pump stops if the tank
temperature (T
2
) reaches the adjustable high limit (T
MAX
)
temperature. The pump A1 runs only when the
temperature at the collector sensor location S1 is higher
than the tank 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
The temperature hysteresis (a lagging in the set-point) may over-ride diff to avoid pump cycling.
U
S1
S2
A1