30
ENG
Heos +0300078EN - rel. 1.6 - 23.11.2017
time
Temp.
Sd-Sv
(F0 = 1)
F5
F1
F1-Frd
F6
FAN
F7
0%
Fig. 6.x
Key
Sd Evaporator probe F1 Evaporator fan activation threshold
Sv Virtual probe Frd Fan activation diff erential
F5 Fan cut-off temperature
F6 is the maximum fan speed, expressed as a % of the output. For 0 to
10 V outputs, it represents the output voltage at maximum speed as
a percentage. The same is true for the minimum speed set for F7. The
fan peak time F8 represents the operating time at maximum speed set
using parameter F6 to overcome the mechanical inertia of the motor.
F9 represents the time the fan is operated at maximum speed for the
peak time (F8). If the fan is kept operating too long at low speed, ice may
form on the blades; to avoid this, every F9 minutes the fan is operated at
maximum speed for the time set for parameter F8.
Sd
(Sd-Sv)
Fan Speed
F6
F7
0%
Frd 1°C
F5
F1
Fig. 6.y
6.9 Electronic valve
Heos can manage Carel E2V single-pole valves (with 6-wire cable).
Double-pole valves (with 4-wire cable) are incompatible with Heos.
To manage the electronic expansion valve, two additional probes must
be installed and suitably confi gured:
• temperature probe for measuring the superheated gas temperature at
the evaporator outlet;
• pressure probe for measuring the saturated evaporation pressure/
temperature at the evaporator outlet
Installation notes:
Heos is designed to manage one electronic expansion valve that controls
the fl ow of refrigerant inside an individual evaporator. Two evaporators
in parallel cannot be managed with just one electronic expansion valve.
The NTC/PTC/PT1000 temperature probe must be installed near the
evaporator outlet, according to the standard installation methods (see
the installation notes on the E2V instruction sheet). Suitable thermal
insulation is recommended. CAREL off ers special types of probes
designed to simplify installation in contact with the refrigerant pipe:
• NTC030HF01 for Retail use IP67, 3m, -50T90 °C, 10 pcs
• NTC060HF01 for Retail use IP67, 6m, -50T90 °C, 10 pcs
To measure the saturated evaporation temperature, diff erent types of
probes can be used; in particular, the following can be installed:
0 to 5 V ratiometric pressure probe (recommended by CAREL);
4 to 20 mA active pressure probes .
Conversion of the pressure to a temperature value is performed
automatically once the refrigerant has been selected (see the paragraph
on the compressor)
Overview screen (screen Dbd01)
Heos manages the proportional opening of the electronic expansion
valve, adjusting the fl ow of refrigerant in the evaporator, so as to maintain
the superheat around the value set for advanced parameter P3 (superheat
set point). The opening of the valve is controlled simultaneously yet
independently from normal temperature control. When there is a
refrigeration call (the compressor is operating), control of the electronic
valve is also activated and then managed independently of compressor
speed. If the superheat value read by the probes is greater than the set
point, the valve is opened proportionally to the diff erence between the
values. The speed of variation and the percentage of opening depend on
the PID parameters set. The opening is continuously modulated based on
the superheat value, with PID control.
Superheat set point (parameter P3)
This is used to set the reference superheat value for the control of the
electronic valve. It does not determine the actual superheat value, but
rather the desired value. Heos, with PID control, tends to maintain the
actual superheat, calculated based on the probe readings, around the
value set for this parameter. This is done by gradually varying the opening
of the valve based on the diff erence between the actual superheat and
the set point.
Par. Description Def U.M.
Min Max
P3 Setpoint superheat 10.0 (36.0) °C (°F) 0.0 (0.0) 30.0 (54.0)
Important: the set point value calculated depends on the quality
of the installation, the position of the probes and other factors.
Consequently, depending on the installation, the set point read may
deviate from the actual value. Set point values that are too low (2...4 K),
albeit ideally usable, may cause problems involving the return of liquid
refrigerant to the compressor.
Valve position at start control (parameter cP1)
This is used to set the position of the valve as a percentage when
control starts. High values ensure intense and immediate cooling of the
evaporator when each call is sent, however may cause problems if the
valve is oversized with reference to the cooling capacity of the controller.
Low values, on the other hand, allow a more gradual and slower action.
The values set should be coherent with compressor start-up speed.
Par. Description Def U.M.
Min Max
Psb Enable EEV opening in standby 0 -- 0 1
CP1 EEV opening at start-up 50 % 0 100
cP2 EEV pre-positioning delay 6 s 0 300.0
PID control of the expansion valve (parameters P4, P5, P6)
The opening of the electronic valve is controlled based on the diff erence
between the superheat set point and the actual superheat calculated by
the probes. The speed of variation, the reactivity and the ability to reach
the set point depend on three parameters:
• Kp = proportional gain, parameter P4;
• Ti = integral time, parameter P5;
• Td = derivative time, parameter P6;
The ideal values to be set vary depending on the applications and the
utilities managed, nonetheless default values are proposed that allow
good control in the majority of cases. For further details, refer to classic
PID control theory.
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