Carel IR32M Manual page 27

Version IR32S with H1=0 (thermostat function):
A4=3: DIRECT/REVERSE OPERATION
The digital input is used to choose the DIRECT function (for refrigeration) or the REVERSE function (for
heating - see also parameter r3). When the contact is open the equipment works in DIRECT mode, when the
contact is closed, in REVERSE. It is therefore possible to connect, for example, a switch which will
command, according to its position, heating or cooling.
If A4=3 the state of the digital input takes priority over parameter r3; that is, the value assigned to r3
becomes immaterial and only the state of (open or closed) of the digital input counts.
All other versions, including IR32S with H1=1:
A4=3: PREPARATION FOR DEFROSTING
It is possible to connect an external contact to the multi-function input to prepare for or to inhibit defrosting.
When the contact is open, defrosting is inhibited, and when closed, defrosting becomes possible. If the
contact is closed, but defrosting has not been requested by the controller, obviously defrosting will not occur.
If the contact is closed and defrosting is under way, any opening of the contact will cause defrosting to be
interrupted immediately, and the equipment will resume normal operation (without carrying out the dripping
or post-dripping phases). The "DEF" LED begins to flash, indicating that the request for defrosting remains
unsatisfied and will await the next consent signal (the closure of the contact).
This function is useful, for example, with refrigerated cabinets fitted with hot gas defrosting. With these
installations it is necessary to defrost an "island" at a time, so at anyone moment, some islands will be
empowered to defrost and others inhibited.
Another use for this function is to inhibit defrosting of those units exposed to the public during shopping
hours. A request for defrosting which arises when the contact is open will remain in waiting until the contact
is closed.
A4=4: INITIATION OF DEFROSTING BY EXTERNAL CONTACT
This function allows activation of defrosting by an external contact. This defrosting has priority over "internal"
defrosting ordered by parameter, or from the keypad. Where defrosting occurs through external contact all
the "d" parameters selected remain valid. In particular it can be useful to set dI=0 so as to permit only
manual or externally ordered defrosting, and excluding defrostings ordered by the internal clock.
This function is useful if is necessary to carry out a defrosting in real time. To do this it is sufficient to
connect a mechanical or electronic timer to the digital input. When the timer contact changes from open to
closed, a request for defrosting is passed. As described under parameter d5, it is possible to link more than
one unit to the same timer. By choosing the value of parameter d5 appropriately for each unit it is possible to
avoid simultaneous defrosting by more than unit.
t
defrost
dP(1)
d5(2)
richiesta sbrinamento
defrost request
defrost
dP(2)
defrost
d5(3)
dP(3)
timer
Explanation:
t = impulse from timer to initiate
defrosting; minimum duration must be
unit 1
0.5 seconds;
dP(1)
defrosting, unit 1;
d5(2) = external contact's defrost delay
unit 2
for unit 2. This must be greater than
dP(1) if two units are not to defrost at
the same time.
unit 3
Similarly for d5(3) and dP(3).
26
= maximum duration
Cod. +030220151 - Rel. 2.1 - 04/09/98
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