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Ascon Tecnologic - e33 - OPERATING INSTRUCTIONS - PAG. 9

5.8

Defrost control

The defrost control acts on the outputs configured as

and

The type of defrost is set by the parameter

ddt

With electrical heating

(or

By stopping compressor

while defrosting, the output

is deactivated while the

output

is enabled. The defrost will be by Stopping

compressor if not using the

output;

With hot gas

Cycle inversion

: while defrosting both

the

and

outputs are enabled:

Without compressor output conditioning

: while de-

frosting, the output

continuous to operate in order to

control thetemperature, also the output

is enabled;

With electrical heating and defrosting temperature
control

: during defrosting, the output

is deactivated

while the output

operate as evaporator temperature

control.

In this mode the defrost lenght is by time-out (time

ddE

During the defrost, the

output behaves as an heating

mode control with Set Point =

dtE

, differential fixed at 1°C

and operates with the values of the

evaporator probe.

5.8.1

Starting automatic defrosts

The automatic control of defrost occours:

–

By interval times (regular or dynamic);

–

By Evaporator temperature;

–

By continuous compressor running time.

In order to avoid unnecessary defrosting when the evapora-
tor temperature is high the

dtS

parameter allows to set the

temperature related to the evaporator probe (probe config-
ured as

) under which defrosts are possible.

Defrost by regular interval time

As an alternative to programmable defrosts, the instrument
allows to execute the defrosts at programmed interval time.
Through the

ddC

parameter, can be set the defrost interval

counting mode:

At real-time power-ON intervals. The

ddi

interval is

counted as the total ignition time of the instrument. This
mode is the one currently used in the refrigeration sys-
tems.

At time intervals of the compressor operation. The

ddi

interval is counted as the sum of the operating times of
the

output (

output activated). This mode is usu-

ally used in refrigeration systems with compressor stop
defrosting.

Defrost cycle at each compressor stop. The instrument

starts a defrost cycle every time the

output is deacti-

vated, when the Set Point is reached or at the expiration
of the interval set with

ddi

paramreter. If

ddi

the

defrost happens only at compressor stop.

This mode is used only on particular refrigerating ma-
chines in which is required the maximum evaporator
efficiency at each compressor cycle.

To enable automatic defrost at intervals, after setting the

ddC

parameter as desired between

, with the ddi pa-

rameter select the time interval between the end of a defrost
and the beginning of the next.
The time that the instrument must wait to perform the first
defrost after power ON can be set with parameter

dSd

. This

allows to perform the first defrost to a different interval from

ddi

time.

To force the instrument to perform a defrost cycle at each

power ON (as long as the conditions set with parameters

dtS

and

dtE

are satisfied) set parameter

dSd

This allows the evaporator to be permanently defrosted,
even when frequent interruptions to power supply occur that
may cause the cancellation of the various defrosting cycles.
If instead it is desired that all the defrosts are performed at
the same interval time, set

dSd

ddi

Setting

ddi

oF the

Automatic defrost function by interval

is totally disabled (including the first, regardless of the time
set to the

dsd

parameter).

Dynamic Defrost Intervals System

ddd

the Dynamic defrost is disabled.

Note:

For this function is necessary to use the evaporator
probe.

To enable the

Dynamic Defrost Intervals System

, program

ddC

and set

ddd

any value

Setting

ddd

, the defrost intervals are those set by the user

and the

Dynamic Defrost Intervals System

is disabled.

This mode allows to dynamically reduce the defrost interval
counting (

ddi

dSd

if is the first defrost), anticipating, when

necessary, the defrost execution, all based on an algorithm that
detects a drop in the refrigerator thermal exchange performance.
The algorithm estimates a reduction in thermal exchange
based on the increase in temperature difference between

Pr1

(cell control) and evaporator probe (probe configured as

). The result is stored by the instrument when the tem-

perature is close to the Set Point setting.
The advantage of the

Dynamic Defrost Interval

is the possi-

bility to program a defrost interval time longer than normal.
In this way, when necessary, the instrument has the pos-
sibility to anticipate the defrost or to start the cycle after the
programmed time.
If the system results correctly set, it is possible to avoid
many unnecessary defrosting cycles (and therefore to obtain
aconsistent energy saving) that may occur with normal op-
eration when, to ensure more system efficiency, the defrost-
ing interval is programmed with a time that is often too short.

Phase

off

Temp.

ddi/dSd

time to defrost Phases 0, 1

Defrost

off

DT0

dtE

dtS

Cool

Defrost