Technical data

Defrost Controlling Loads • 9
Opening percentage is the percentage of the cycle
period where the valve is open. For example, if
CyP=6s (standard value) and the valve is opened at
50%, this means that the valve is opened for 3 sec-
onds during the cycle period.
8.2.1. First Kind of Regulation:
Standard Regulation
In this case, the Hy parameter is the differential for
the standard ON/OFF regulation. In this case, the int
parameter is neglected. The regulation follows the di-
agram shown in Figure 8-2:
8.2.2. Second Kind of Regulation:
Continuous Regulation (For
Model XM679K Only)
In this case, the Hy parameter is the proportional
band of PI in charge of room temperature regulation.
It is advisable to use at least Hy=5.0°C/10°F.
The int parameter is the integral time of the same
PI regulator. Increasing the int parameter will cause
the PI regulator to react more slowly, and is true vice
versa. To disable the integral part of regulation, set
int=0.
8.3. Defrost
8.3.1. Defrost starting
In any case, the device checks the temperature that
is read by the configured defrost probe before starting
defrost procedure. After that:
• If RTC is present, two defrost modes are available
through the tdF parameter: defrost with electrical
heater and hot gas defrost. The defrost interval is
controlled by parameter EdF: (EdF = rtc) defrost is
made in real time depending on the hours set in the
parameters Ld1..Ld6 in workdays, and in
Sd1…Sd6. On holidays: (EdF = in) the defrost is
made every IdF time.
• Starting defrost cycles can be operated locally (man-
ual activation by means of the keyboard or digital in-
put or end of interval time) or the command can
come from the Master defrost unit of the LAN. In
this case, the controller will operate the defrost cycle
following the parameters it has programmed, but at
the end of the drip time it will wait until all the other
LAN controllers finish their defrost cycle before the
normal regulation of the temperature is restarted ac-
cording to the dEM parameter.
• Every time any of the LAN controllers begin a de-
frost cycle, it issues the command to the network
making all the other controllers start their own cycle.
This allows a perfect synchronization of the defrost
in the whole multiplexed cabinet according to LMd
parameter.
• By selecting the dPA and dPb probes and changing
the dtP and ddP parameters, defrost can be started
when the difference between the dPA and dPb
probes is lower than dtP for all ddP time. This is
useful to start defrost when a low thermal exchange
is detected. If ddP=0, this function is disabled.
Figure 8-1 - Regulation via PI Regulator
Figure 8-2 - First Kind of Regulation
Figure 8-3 - Second Kind of Regulation