The EWPC 961 is a temperature
controller specifically designed for
refrigeration applications and pro-
vides time control for off-cycle de-
frost management.
GENERAL DESCRIPTION
The EWPC 961 is a temperature controller
specifically designed for refrigeration appli-
cations and provides time control for off-
cycle defrost management.
It incorporates an output relay for com-
pressor control and a PTC sensor input.
A number of parameters are displayed al-
phanumerically to set up the instrument for
each specific application.
The EWPC 961 is supplied in the popular
“32x74” ELIWELL.
OPERATION
The EWPC 961 is designed to operate
strictly as a cooling control, which means
that the switching differential is positive:
the compressor cuts off at setpoint and is
started at a temperature of set plus differ-
ential. The on-board microprocessor pro-
vides several timing functions for the
defrost; the defrost cycle as well the de-
frost cycle duration are user selectable.
At the start of each defrost cycle, the com-
pressor is simply stopped, regardless of
the temperature control circuit.
In addition, the EWPC 961 offers several
system protection features, all easy to un-
derstand and easy to program.
FRONT KEYPAD
SET: push to display the setpoint temper-
ature; the “DEF/SET” status light will blink.
The setpoint can be changed within 5 sec-
onds with the “UP” or “DOWN” button.
The control will automatically switch back
to normal operating mode within 5 sec-
onds; the last entered setpoint will stay in
memory.
UP: used to increase the setpoint value, as
well as the parameter when in program-
ming. When held down for a few seconds,
the change rate accelerates.
DOWN: same functions, except to de-
crease a value.
DEFROST: push to initiate a manual de-
frost cycle (override of programmed de-
frost start; programmed time resets to
zero). Manual defrost can not be started
while in setpoint or in parameter program-
ming mode. This button must be activated
for 3 seconds to start a defrost; the
“DEF/SET” status light will come on and
the compressor is stopped.
Led “COMP”: status light of the compres-
sor output.
Led “DEF/SET”: blinks during setpoint
display/change. When Led is on the de-
frost is in progress.
PARAMETER PROGRAMMING
Programming is easily accessed by hold-
ing the “SET” button down for more than
4 seconds; the first parameter is displayed
while the status light “DEF/SET” remains
blinking during the programming period.
Other parameters are accessed with the
“UP” and “DOWN” button.
With the “SET” button, the actual setting of
each parameter is displayed. To change a
parameter setting, push the “SET” plus the
“UP” (or “DOWN”).
The system will automatically return to its
normal operating mode a few seconds af-
ter the programming procedure is com-
pleted or interrupted.
DESCRIPTION OF PARAMETERS
d: differential.
LS: Lower Set.
Setting of the lower user-access setpoint
limit.
HS: Higher Set.
Setting of the upper user-access setpoint
limit.
CA: CAlibration.
Temperature read-out offset to allow for
possible error due to probe location.
rP: relay Protection.
Select relay status in case of probe defect.
on = compressor ON in case of probe de-
fect;
HOW IT IS MADE
• Housing: black ABS plastic, self-
estinguishing
• Dimensions: front 74x32 mm
(2.913x1.260"), depth 67 mm
(2.637")
• Protection: the instrument front-
panel is waterproof IP65; an op-
tional snap-on cover can be
supplied to provide additional pro-
tection of the rear terminal block
• Connections: screw terminal
block (2.5 mm
2
; one wire each ter-
minal onl)
• Display: 12.5 mm LED (0.50")
• Push buttons: located on front
panel
• Output: one (1) SPDT relay 8(3)A
250Va
• Input: PTC probe
• Resolution: 1 °C (°F)
• Accuracy: better than 0.5% of full
scale
• Power supply (depending on mod-
el): 12 Va/c or 24 Va/c
WHAT IT IS
EWPC 961
freezer controls
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