1
Introduction
he USDT 2005 unit is an analog temperature differential controller. It can be used in a
wide range of applications. At the factory, it is set to control a simple solar water heating
system.
Solar System Control (S) Mode
In this program mode, it ensures that the collected energy from the sun is transferred efficiently,
and harnessed under optimum conditions. It monitors the collector temperature (T
KS
) and the
return temperature (T
BS
, bottom of the storage tank). The
solar loop circulation pump runs while the collector
temperature exceeds the return temperature by an
adjustable temperature difference ?T. To avoid
overheating, the circulation pump stops if the return
temperature (T
BS
) reaches the adjustable high limit (T
MAX
)
temperature. The temperature hysteresis (a lagging in the
set-point) may over-ride ?T 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 ?T. The pump stops
if ?T is less than the preset value or, the if the temperature
at location S2 (storage tank) has reached the
T
MAX
A1 (ON) only when S1 > (S2 + diff)
& S2 < max
Boiler Control (L) Mode
The User can switch USDT 2005 to operate a boiler circulator. In boiler mode (L), the pump runs
only when boiler temperature at S1 location
is higher than the minimum set point dialer
and the ?T condition is satisfied.
A1 (ON) only when S1 > max &
S1 > (S2 + diff)
Note:
The maximum temperature dialer
(
max)
serves as the minimum starting
temperature,
T
MIN
in the boiler mode. User
must change the switch position on the back
of the circuit board to use the USDT 2005 as a boiler controller. Details will follow.
MAX
set point protects the solar system from overheating. It turns off the circulator if the boiler
contribution to the storage tank is not satisfied.
T
S1
S2
A1
S2
A1
S1
