Carel plug-in User Manual page 28

For all models, including S with H1=1:
A4 = 2: enable defrost
An external contact can be connected to the multifunction input to enable or inhibit the defrost function. When the contact is open,
the defrost is inhibited, while it is enabled when the contact is closed. If the contact is closed and there is no request from the
controller, obviously the defrost is not performed. If the contact is closed and a defrost is in progress, opening the digital input
immediately stops the defrost and the unit returns to the normal operation (without performing the dripping phase). Upon request
for a defrost the corresponding defrost LED starts to flash, until the next enabling action (closing of the contact). This function is
useful, for example,, in the case of multiplexed showcases with hot gas defrost. These systems must be defrosted by island and
thus, at any one moment, some islands are enabled for defrost, while others are inhibited. Another use of the function is to prevent
defrosting the units available to the public during opening hours. Any defrost requests when the contact is open will stay on hold
until the closing of the contact.
A4 = 3: start defrost from external contact
This function allows the defrost to be started from an external contact. If the defrost is started using an external contact, all the type
'd' parameters selected are valid. In particular, it may be useful to set dI=0 to enable manual defrosts or defrosts from external
contact only, excluding defrosts generated by the internal clock.
This function is useful in the case where real time defrosts are required. To perform these, simply connect a mechanical or
electronic timer to the digital input. When the contact of the timer moves from open to closed it enables the defrost request.
It may be the case, as mentioned in the description of parameter d5, that more than one unit is connected to the same timer.
Selecting a different value for d5 for each unit will avoid simultaneous defrosts.
Warning: the minimum duration must be 0.5 seconds.
t
defrost
dP(1)
d5(2)
defrost request
A4 = 4: curtain switch / night-time operation
Setting parameter A4 =4 manages the contact which signals the closing of the curtain on showcases or modifies the set point for
night-time operation. With the contact closed the set point is modified by the value r4 (set point variation for night-time
operation).
A4 =5
Only for S1A mod.: A4= 5: active direct/reverse function
Other models: A4= 5 / 0: inout no active
The following table summarises the functions assumed by the multifunction digital input, according the setting of A4.
value parameter A4 meaning
0 input not active
1 external alarm instant or delayed (A7)
2 enable defrost (closed = enabled)
3 start defrost on closing
4 curtain switch or night-time operation
5 Direct/Reverse selection
Warning: parameter A4 is accessible on all models, but can only be used on those which effectively have the input, in alternative
to the second probe. When the input is not present, the value of A4 must be zero (0), indicated by the – (dash) in Tab. 4.8.2.
Cod. +030221881 rel. 1.5 - 26/10/10
defrost
dP(2)
d5(3) defrost
dP(3)
Key:
timer
t = impulse from the timer to start the defrost;
dP(1) = maximum defrost duration, unit 1;
d5(2) = defrost delay from external contact for unit 2. This
must be greater than dP(1), to avoid defrosting at the same
unit 1
time.
The same is true for d5(3) and dP(3) for unit 3.
unit 2
unit 3
S Y X
  
 
-
 
-
 
-
 
-

- -
Tab. 4.8.2
28
Fig. 4.8.2
C

-
-
-
-
-
plug-in