Carel FLSTDMAHUE, User Manual

Page: 44 / 94

ENG
“FLSTDMAHUE” +030220961 - rel. 1.1 - 28.08.2019
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Example 2: overlapping of preheating and reheating coils.
100%
0%
Heating
Free_heat/
Reheat
Device_opening
recovery
50% 66% 100%
Req
33%
Preheat
Key
Recovery Recovery Req Request
Free_heat Freeheating Device_opening Device activation
Preheat Preheating coil valve Reheat Reheating coil valve
9.11 Supply limits
Definition
Note : the supply limits function can be activated (Gfc04) only if the
control probe is the return probe or room probe .
The algorithm is used to correct the action of the main control function to
return within acceptable values for the supply temperature. For example,
if the fresh air damper opens to satisfy a air quality request, this attenuates
the request on the actuators (e.g. heating coil, humidifier) so as to mitigate
the effect on the supply temperature and humidity. Without this function,
the supply air may cause discomfort (e.g. too hot or too cold) near the air
inlets. The function can be activated on either the minimum or maximum
temperature or humidity. There are two possible cases: action concordant
with or contrasting against control.
Temperature limits with concordant action
Example of operation in heating mode (winter): when the control set point
is reached and the heating coil stops heating, an air quality request causes
the fresh air damper to open and consequently the air supply temperature
decreases. To prevent the temperature measured by the control probe from
changing further, when the air supply temperature is less than minimum
allowed limit the heating coil is activated, with proportional or PI control,
according to the following graph, where the total request is 50%.
100%
0%
Req_heat
Reg_temp
Set
NZ_heat diff_heat
100%
0%
Req_lim_heat
Supply_temp
Low_limit_temp
diff
50%
0 % + 5 0 % = 5 0 %
Key
Req_lim_ heat Additional heating
request
Reg_temp Control probe
temperature
NZ_heat Neutral zone in heating Supply_temp Supply probe
temperature
Diff_heat Heating differential Diff Supply limit differential
The behaviour is similar in cooling mode (summer).
100%
0%
Req_cool
Reg_temp
diff_cool NZ_cool
100%
0%
Req_lim_cool
Supply_temp
diff
High_limit_temp
50%
0 % + 5 0 % = 5 0 %
Key
Req_lim_cool Additional cooling
request Reg_temp Control probe
temperature
NZ_cool Neutral zone in cooling Supply_temp Supply probe tempe-
rature
Diff_cool Cooling differential Diff Supply limit
differential
High_limit_ temp High temperature limit
Screen index Display description Selection
Gfc04 Temperature regulation
Auto cool/heat
No ¦ Yes
Supply limits None ¦ High ¦ Low ¦
High/low
Alto/basso
Screen index Display description Def Min Max UOM
Gfc07 Temperature supply limits
Summer high
40 -99.9 99.9 °C
Winter high 40 -99.9 99.9 °C
Summer low 10 -99.9 99.9 °C
Winter low 10 -99.9 99.9 °C
Differential 3 0 99.9 °C
Integral time 150 0 999 s
Humidity limits with concordant action
Example of operation in humidification mode: when the control set point
is reached and humidification ends, an air quality request causes the fresh
air damper to open and consequently the supply humidity may decrease.
To prevent the humidity measured by the control probe from changing
further, when the supply air humidity is less than minimum allowed limit,
the humidifier is activated, with proportional or PI control, according to the
following graph, where the total request is 50%.
100%
0%
Req_hum
Reg_hum
Set
NZ_hum diff_hum
100%
0%
Req_lim_hum
Supply_hum
Low_limit_hum
diff
50%
0 % + 5 0 % = 5 0 %
Key
Req_lim_hum Additional
humidification request Reg_hum Control probe
humidity
NZ_hum Neutral zone in
humidification Supply_hum Supply probe
humidity
Diff_hum Humidification
differential Diff Supply limit
differential
Low_limit_hum Low humidity limit
The behaviour is similar in dehumidification mode
100%
0%
Req_dehum
Reg_hum
diff_dehum
NZ_dehum
100%
0%
Req_lim_dehum
Supply_hum
diff
High_limit_hum
50%
0 % + 5 0 % = 5 0 %
Key
Req_lim_dehum Dehumidification
request for limit Reg_hum Control probe
humidity
NZ_dehum Neutral zone in
dehumidification Supply_hum Supply probe
humidity
Diff_dehum Dehumidification
differential Diff Supply limit
differential
High_limit_hum High humidity limit
Screen index Display description Selection
Gfc10 Humidity regulation
Auto hum/dehum
No ¦ Yes
Supply limits None ¦ High ¦ Low ¦
High/low