Generic Functions; Stages - Carel PRK300L3FK User Manual

ENG
For activation by probe, the operation of the On/Off or modulating
3-way valve and the pump is shown in the fi gure, where the temperature
considered is the heat recovery exchanger outlet temperature:
Heat reclaim by probe
Modulating valve
Differential
Setpoint
If the probe is not working, pRack pR300 considers the other conditions,
without Signalling further alarms in addition to the probe alarm.
As regards activation from time bands, heat recovery does not consider
the operating seasons, and links can be set to special days and closing
periods so that heat recovery is only active based on the daily bands set.
Note:
•
a settable bottom limit is available for the condensing pressure, below
which heat recovery is deactivated.
•
condensing pressure set point compensation can be disabled when
heat recovery is active..
Heat recovery as the fi rst stage in high pressure prevention
Heat recovery can be used to prevent high condensing pressure. The
parameters relating to this function can be set in branch G.b.a/G.b.b of
the main menu, after having enabled the heat recovery function.
For details on operation of the prevent function, see paragraph 8.3.3. Heat
recovery operation as the fi rst stage in high pressure prevention is shown
in the fi gure:
Heat reclaim
Diff. Diff.
Offset
Heat reclaim activation
The function must be enabled and an off set must be set in relation to
prevent threshold, while the diff erential is the same set for the prevent
function.
6.6.4

Generic functions

pRack pR300 can use the free inputs /outputs and certain internal
variables for generic functions.
Important: The generic functions are available on pRack pR300
boards with pLAN addresses from 1 to 4, that is, on all boards that
manage a suction or condensing line, nonetheless only the parameters
corresponding to the functions managed by boards 1 and 2 are sent to
the supervisory system.
The following generic functions are available for each board:
•

5 stages

•
2 modulations
•
2 alarms
•
1 scheduler
Each function can be enabled/disabled by digital input and from the user
interface.
pRack +0300025EN rel. 1.3 - 17.12.2015
Pump and ON/OFF valve
Differential Outlet temperature
Fig. 6.af
Prevent
Cond. Press.
Diff. Diff.
Prevent threshold
Fig. 6.ag
The generic functions can be enabled and the related parameters set in
main menu branch E.f. To be able to use the free inputs, these must be
confi gured as generic probes from A to E (analogue inputs) and generic
inputs from F to J (digital inputs), consequently a maximum of 5 analogue
and 5 digital inputs can be used. After having confi gured the generic
probes, the associated variables can be used as control variables and the
digital inputs as enabling variables.
As well as the generic probes and inputs, pRack pR300 software internal
variables can be used, depending on the system confi guration. Some
examples are, for analogue variables:
•
Suction pressure
•
Condensing pressure
•
Saturated suction temperature
•
Saturated condensing temperature
•
Suction temperature
•
Discharge temperature
•
% of compressors active
•
% of fans active
•
Superheat
•
Subcooling
•
Liquid temperature,
•
% compressor request
•
% fan requesti
And for the digital variables:
•
High suction pressure alarm
•
Low suction pressure alarm
•
High condensing pressure alarm
•
Sign of life
•
Prevent active
Each generic function can be associated with a unit of measure and a
description. Below is a description of the operation of four types of
generic functions.
Stages
pRack pR300 can manage up to 5 stage functions, with either direct or
reverse operation. In both cases, a set point and a diff erential can be set; the
operation of the corresponding output is shown in the fi gure for both cases:
Direct stage
Diff.
Setpoint
Reverse stage
Diff.
Setpoint
If an enabling variable has been set, the corresponding output is active if
the enabling is also active.
For each stage, a high alarm threshold and a low alarm threshold can be
set, and are absolute. For each alarm, the activation delay and priority can
be set. See chapter 8 for details on the alarms.
One example of using the generic stage functions may be activation of
the fans on the room units based on the temperature.
46
Regulation variable
Diff.
Regulation variable
Diff.
Fig. 6.ah