ECKELMANN UA 300 D, Manual

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Function of UA 300 D
8 Version 2.03 27. Juni 2008
3.2.2 Compressor control
3.2.2.1 Control by temperature according to majority (UA 111 X only)
A maximum of two compressors are controlled by the base load/peak load principle. Control is made by case
temperature through all supply air sensors. The peak load compressor is stopped when temperature has re-
ached the setpoint (switch−off value) on the majority of the connected supply air sensors (e.g. 3 out of 5).
The base load compressor is stopped when temperature reaches the setpoint on the last supply air sensor. It is
started again when temperature has passed the switching differential on the majority of the supply air sensors.
ON delay always expires consecutively for Compressors 1 and 2, meaning that they will never start simulta-
neously even when two compressors are demanded at once by all sensors.
OFF delay may expire concurrently (when all sensors turn cold at once), meaning that both compressors may
stop.
The peak load compressor is restarted when temperature has passed the switching differential on all supply air
sensors. Base load rotation is provided to avoid varying run times of the base and peak load compressors.
Base load rotation takes place not later than after 3 hours of operation or when the following control operations
occur.
(P = 0 / B = 0)
³
(P = 0 / B = 1) or
(P = 1 / B = 1)
³
(P = 0 / B = 1)
P = peak load compressor / B = base load compressor / Transition from one control state to the next.
Both compressors are stopped immediately if the set antifreeze protection temperature is reached. They are
both restarted after an adjustable time delay has elapsed.
3.2.2.2 Antifreeze protection
The supply air sensor on which temperature is the coldest causes cooling to be stopped if temperature drops
below the set antifreeze protection level. This prevents freeze−up and damage to merchandise in individual dis-
play cases controlled at very cold temperature to accommodate special requirements of placement or the like.
3.2.2.3 Control by pressure switch with neutral zone (UA 111 XP only)
Control is made as a function of pressure by a pressure switch with neutral zone connected to two digital inputs.
This pressure switch is installed in the refrigerant line and compares pressure in the refrigerant line with a refe-
rence pressure.
If the pressure is lower or higher, the pressure switch actuates a 230V digital input at the refrigeration point.
When a 230 V signal is applied to the compressor loading input, one additional compressor is started after an
adjustable load time. When a 230 V signal is applied to the compressor unloading input, one additional com-
pressor is stopped after an adjustable unload time. A maximum of three compressors can be controlled. They
can be enabled separately. A maximum number of compressor starts per hour can be defined.
Base load rotation takes place every time a compressor is loaded or unloaded, not later than after 2 hours. Both
compressors are stopped immediately if the set antifreeze protection temperature is reached. They are both re-
started after an adjustable time delay has elapsed.
Forced actuation can also be set in minutes. This means that a compressor will be actuated if none has been
demanded by the pressure switch within the set interval. The time is started as soon as a cooling relay is energi-
zed. If forced actuation is active, the pressure switch will not be interrogated again until an adjustable bypass
interval has expired.
This allows the system to build up pressure with the forced−control compressor and, in the least favorable in-
stance, to move the pressure switch out of the unload position.