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Figure 7-1 - Regulation via PI Regulator
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 three (3)
seconds during the cycle period.
7.2.1. 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
diagram shown in Figure 7-2:
Figure 7-2 - First Kind of Regulation
7.2.2. Second Kind of Regulation:
Continuous Regulation
(For Model XM679 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=10°F/ 5.0°C.
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.
Defrost
Figure 7-3 - Second Kind of Regulation
7.3. Defrost
7.3.1. Defrost starting
In any case, the device checks the temperature that is
read by the configured defrost probe before starting
defrost procedure. After that:
• Starting defrost cycles can be operated locally
(manual activation by means of the keyboard or
digital input 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 according to the dEM parameter.
• Every time any of the LAN controllers begin a
defrost 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.
7.3.2. Defrost Ending
• If dPA and dPb are present and d2P=y, the
controller stops the defrost procedure when dPA is
higher than the dtE temperature and dPb is higher
than the dtS temperature.
At the end of defrost, the drip time is controlled
through the Fdt parameter.
Controlling Loads • 9
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