Carel Heos, User Manual

Page: 33 / 60

33
ENG
Heos +0300078EN - rel. 1.6 - 23.11.2017
PI control
Inputs
The room humidity (SU) and temperature (SA) probes can be (see
parameters /FL, /FI):
•
connected to the Master, which automatically shares them with the Slaves;
•
connected locally to each controller;
•
sent from the supervisor via the serial probes.
Alternatively, the supervisor can directly supply the dew point value
(Sdp) using the serial probes. The glass temperature probe (Svt) can be
connected directly to each controller (see parameter /FM), or estimated.
The estimate of the glass temperature probe reading is performed
internally when: room temperature (SA), outlet temperature (Sm) and
intake temperature (Sr) are available, and depends on parameters Ga, Gb
and Gc. Parameters rHo, rHd determine the modulating output.
Par. Description Def U.M. Min Max
Ga Coeffi cient a” for glass temperature formula 2.0
(35.6) °C
(°F) -20.0
(-4.0) 20.0
(68.0)
Gb Coeffi cient b” for glass temperature formula 22 % 0 100
Gc Coeffi cient c” for glass temperature formula 80 % 0 100
rHo Anti-sweat modulation off set from dew point 2.0
(3.6)
°C
(°F) -20.0
(-36.0) 20.0
(36.0)
rHd Anti-sweat heater diff erential modulation 0.0
(0.0) °C
(°F) 0.0
(0.0) 20.0
(36.0)
Svt = (SA - Ga -3) - Gb • (SA - Ga - Ti)
100
dove:
Ti = Sm • Gc + Sr • (100 - Gc)
100
If one of the probes is not available (SA or either Sm or Sr), only fi xed
activation control will be possible, based on parameters rHu and rHt.
Outputs
The analogue output for the anti-sweat function can be 0-10 VDC
(analogue output Y1, Y2, Y3) or PWM (SSR output OUT2).
If using the 0 to 10 Vdc output, the output voltage will vary based on the
anti-sweat control activation percentage (see Fig. 6.ad). This output can
be used to directly control an FCS controller, for example.
If using SSR output Out2, the output will be active for a time that is
proportional to the function activation percentage (see Fig. 6.ad), with a
period equal to rHt (manual anti-sweat activation time, settable between
1 min and 30 min).
The anti-sweat control activation percentage (OUT) depends on the
diff erence between the dew point calculated and the glass temperature
probe value (measured or estimated), on the value of parameter rHo
(off set), the value of parameter rHd (diff erential), the Cutoff (rhB) and the
hysteresis (rHC) (see the following fi gure).
Svt
Out
Max
Min
0%
Sdp
rHo rHd
rHC
Cutoff
rHB
Fig. 6.ac
Key
Sdp Dew point Svt Glass temperature probe
rHo Anti-sweat heater modulation off set Min Minimum anti-sweat
output value
rHd Anti-sweat heater modulation diff erential Max Maximum anti-sweat
output value
OUT Anti-sweat controller
Min: minimum output fi xed at 10%; Max: maximum output fi xed at 100%.
The action is only proportional if the estimate of the glass temperature
is used, and proportional and integral (Tint=240 s, constant) if the actual
glass temperature probe is used. The aim of the integral action is to bring
the glass temperature towards the set point (Sdp+rHo).
Important: if using supervisor serial probes to propagate the
room temperature, humidity or dew point values, the Heartbeat on the
“Dew point propagation plugin” needs to be set appropriately. This is
used by the HEOS controller to understand whether the supervisor is
continuing to send new values. If Heos does not receive any new values
for more than 30 minutes, alarm ACE is signalled and manual control
(fi xed activation) is activated. This is useful in the event of power failures
on the supervisor.
The probe not updated alarms are normally displayed when the unit is
fi rst started, i.e. when the variables have yet to be initialised.
Fixed activation control (manual control)
Control depends only on parameters rHu and rHt and follows the trend
shown in the fi gures.
Par. Description Def U.M. Min Max
rHt Anti-sweat heater activation period 30 min 10 180
rHu Manual activation anti-sweat heaters percen-
tage 0: disabled (NO); 70 % 0 100
time
Out
0
(OFF)
10 Vdc
(ON)
rHu
rHt
Fig. 6.ad
Key:
rHu Manual anti-sweat activation percentage
rHt Manual anti-sweat activation time
OUT Anti-sweat controller
6.12 Condenser control
Heos can also optimise the condenser control (generally water-cooled)
to improve system effi
ciency. Control is normally performed based on
the condensing pressure/temperature, however can also use the water
temperature; there are two main types of valves, two-way or three-
way mixing valves. In certain special cases (for example, when ambient
heat can be recovered from), air-cooled condensers can also be used;
in this case, control is performed based on the condensing pressure/
temperature. Consequently, two types of condenser can be chosen
on screen Daa06 (displayed only if both analogue outputs have been
activated): water-cooled and air-cooled
Water-cooled condenser
Below is the water connection diagram with two-way valve. In this case,
the fl ow-rate is modulated so as to stabilise the condensing temperature.
Cooled GAS
Hot GAS
0...10V
T
water in
T
cond
T
water out
M
Fig. 6.ae
Note : a variable fl ow-rate pump must be used in the water loop so
as to respond to the variations required by the various cabinets/
showcases.