20
TK 55032-18-OP-EN
Operating Instructions
Introduction
In vehicle powered units, temperature control is based on two values: The
setting (Setpoint) of the controller and the evaporator return air temperature.
The difference between these two temperatures will determine the mode of
operation: cool, heat, or null.
C
Co
oo
oll:: When the temperature in the compartment is 3°F (2°C)
h
hiig
gh
he
err
than the
setpoint, the unit runs in cool mode to reduce the evaporator return
temperature to achieve the setpoint.
H
He
ea
att:: When the temperature in the compartment is 3°F (2°C)
llo
ow
we
err
than the
setpoint, the unit changes to heat mode to raise the evaporator return
temperature to achieve the setpoint.
N
Nu
ullll:: Once the Setpoint Temperature has been reached, and the
temperature remains at or within the temperature differential, (there is no
demand for heat or cool), the unit stops operating and goes into the Null
mode.
While in the Null mode, the unit is still monitoring the compartment
temperature and will resume operation only if the temperature increases or
decrease by 3°F (2°C) above or below the setpoint.
D
De
effrro
osstt:: After a period of time in cool mode, (time is setup during
installation between 0 and 8 hours), the unit checks the coil temperature. If
the temperature is cold enough to form ice, the unit runs in automatic
Defrost Mode to eliminate ice that has accumulated in the evaporator coil.
Defrost can also be initiated manually by selecting the defrost mode on the
DSR controller. The unit will run in defrost until one of the two events occurs:
1) the coil temperature is back within range, or 2) the defrost termination
timer has expired. (time is setup during installation).
N
No
otte
e:: The return air temperature will increase slightly while in defrost,
however it will quickly return to the desired setpoint after completion
of the defrost cycle.
