Carel EVD Evolution Twin, Руководство пользователя

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ENG
“EVD Evolution TWIN” +0300006EN - rel. 2.6 - 31.01.2019 31
6.5 Control status
The electronic valve controller has 8 different types of control status, each of
which may correspond to a specific phase in the operation of the refrigeration
unit and a certain status of the controller-valve system.
The status may be as follows:
•
forced closing
: initialisation of the valve position when switching the
instrument on;
•
standby : no temperature control, unit OFF;
•
wait
: opening of the valve before starting control, also called pre-
positioning, when powering the unit and in the delay after defrosting;
•
control
: effective control of the electronic valve, unit ON;
•
positioning : step-change in the valve position, corresponding to the start
of control when the cooling capacity of the controlled unit varies (only for
LAN EVD connected to a pCO);
•
stop
: end of control with the closing of the valve, corresponds to the end
of temperature control of the refrigeration unit, unit OFF;
•
valve motor error recognition
: see paragraph 9.5;
•
tuning in progress
: see paragraph 5.3
F orced closing
Forced closing is performed after the controller is powered-up and
corresponds to a number of closing steps equal to the parameter “Closing
steps”, based on the type valve selected. This is used to realign the valve to
the physical position corresponding to completely closed. The driver and the
valve are then ready for control and both aligned at 0 (zero). On power-up, first
a forced closing is performed, and then the standby phase starts.
Parameter/description Def. Min. Max. UOM
VALVE
EEV closing steps
500 0 9999 step
Tab. 6.g
The valve is closed in the event of power failures with 24 Vac power supply
when the EVD0000UC0 module is connected. In this case, the parameter
“Forced valve closing not completed”, visible only on the supervisor, is forced
to 1. If when restarting forced closing of the valve was not successful:
1.
the Master programmable controller checks the value of the parameter
and if this is equal to 1, decides the best strategy to implement based on
the application;
2.
EVD Evolution twin does not make any decision and positions the valve as
explained in the paragraph “Pre-positioning/start control”. The parameter
is reset to 0 (zero) by the Master controller (e.g. pCO). EVD Evolution
twin resets the parameter to 0 (zero) only if forced emergency closing is
completed successfully
S tandby
Standby corresponds to a situation of rest in which no signals are received to
control the electronic valve. This normally occurs when:
•
the refrigeration unit stops operating, either when switched off manually
(e.g. from the button, supervisor) or when reaching the control set point;
•
during defrosts, except for those performed by reversing of the cycle (or
hot gas bypass).
In general, it can be said that electronic valve control is in standby when the
compressor stops or the control solenoid valve closes. The valve is closed or
open according to the setting of “Valve open in standby”. The percentage of
opening is set using “Valve position in standby”.
In this phase, manual positioning can be activated.
Parameter/description Def. Min. Max. UOM
CONTROL
Valve open in standby
0=disabled=valve closed;
1=enabled = valve open 25%
0 0 1 -
Valve position in standby
0 = 25 % (*)
1…100% = % opening (**) 0 0 100 %
Tab. 6.h
These two parameters determine the position of the valve in standby based
on the minimum and maximum number of valve steps.
Parameter/description Def. Min. Max. UOM
VALVE
Minimum EEV steps
50 0 9999 step
Maximum EEV steps 480 0 9999 step
Tab. 6.i
(*) The formula used is:
steps
Max_step_EEV
0
25%
Min_step_EEV
Apertura / Opening =
Min_s(Max_step_EEV-Min_step_EEV)/100*25
Fig. 6.b
(**) In this case, the formula used is:
steps
0%
1%
99%
Apertura / Opening = P*(Max_step_EEV / 100)
Min_step_EEV
100%
Max_step_EEV
P = Posizione valvola in stand-by / Position valve in stand-by
Fig. 6.c
Note : if “Valve open in standby=1”, the positions of the valve when
setting “Valve position in standby”=0 and 25 do not coincide.
Refer to the above formulae.
Prepositioning/start control
If during standby a control request is received, before starting control the
valve is moved to a precise initial position.
The pre-position time is the time the valve is held in a steady position based
on the parameter “Valve opening at start-up”.
Parameter/description Def. Min. Max. UOM
CONTROL
Pre-position time
6 0 18000 s
Valve opening at start-up (evaporator/valve
capacity ratio) 50 0 100 %
Tab. 6.j
The valve opening parameter should be set based on the ratio between the
rated cooling capacity of the evaporator and the valve (e.g. rated evaporator
cooling capacity: 3kW, rated valve cooling capacity: 10kW, valve opening =
3/10 = 33%).
If the capacity request is 100%:
Opening (%)= (Valve opening at start-up);
If the capacity request is less than 100% (capacity control):
Opening (%)= (Valve opening at start-up) x (Current unit cooling capacity),
where the current unit cooling capacity is sent to the driver via pLAN by the
pCO controller. If the driver is stand-alone, this is always equal to 100%.
Note:
•
this procedure is used to anticipate the movement and bring the valve
significantly closer to the operating position in the phases immediately
after the unit starts;
•
if there are problems with liquid return after the refrigeration unit starts or
in units that frequently switch on-off, the valve opening at start-up must be
decreased. If there are problems with low pressure after the refrigeration
unit starts, the valve opening must be increased.
W ait
When the calculated position has been reached, regardless of the time taken
(this varies according to the type of valve and the objective position), there
is a constant 5 second delay before the actual control phase starts. This is to
create a reasonable interval between standby, in which the variables have no
meaning, as there is no flow of refrigerant, and the effective control phase.