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31
ENG
MasterAria +030220481 - rel. 1.0 - 12.11.2007
Par
Description
Def1 Def2 Def3 Min
Max
UOM
22
Select optional compensation probe
0
Compensation disabled
1
Compensation enabled on B1 = outside probe
2
Compensation enabled on B3 = outside probe
0
0
0
0
2
---
23
Set point delta for compensation in cooling (0 = Compensation disabled)
0
0
0
-99
127
°C/10
24
Factor for compensation in cooling (0 = Compensation disabled)
0
0
0
-20
20
---
25
Set point delta for compensation in heating (0 = Compensation disabled)
0
0
0
-99
127
°C/10
26
Factor for compensation in heating (0 = Compensation disabled)
0
0
0
-20
20
---
Tab. 4.h.18
4.3 Outlet limits
Outlet limits are particularly useful in applications where the AHU is
controlled based on the return (intake) or room temperature, and have
the purpose of preventing air that is too cold or too hot from being
introduced into the environment. To do this, these limits act directly on
the heating and cooling devices, bypassing the other algorithms.
Minimum outlet limit on the cold water valve
ON
OFF
90 s
100%
0%
TM
TMm
TMm - Diff
t
t
t
VF
S
Fig. 4.s
Key
t
time
TM
outlet temperature
VF
cooling valve
TMm
min outlet temp. (P106)
S
damper
Diff
outlet limit diff . (P126)
Cold water valve:
1.
when the outlet temperature falls below the
minimum outlet temperature (TMm), MasterAria starts closing the
cold water valve until closing completely at the value of (TMm-Diff ).
Outside damper:
2.
if a modulating damper is used and freecooling/
heating management is available, the outlet limit acts on the damper
only if the action on the cooling coil is not suffi
cient. If 90 seconds after
closing the valve the outlet temperature continues to remain below
the minimum outlet temperature minus a diff erential, the damper is
moved to the minimum position (P119). For ON/OFF dampers, the
damper is closed.
While the outlet limit conditions remain, the integral action of the control
algorithm is suspended.
Par
Description
Def1 Def2 Def3 Min
Max
UOM
106
Minimum cooling valve/
heating valve-heater
outlet temperature
127
18
18
-28
127
°C
119
Minimum outside
damper position
0
20
20
0
100
%
126
Outlet limit diff erential
20
20
20
10
255
°C/10
Tab. 4.i
Minimum outlet limit on the hot water valve (heating
only)
During the winter period, there are two cases in which the minimum
outlet limit may be enabled:
when the room temperature reaches the set point and the heating coil
•
closes completely, if the outside air is too cold a situation of discomfort
will be created inside the environment near the air distributors;
when freecooling is active in crowded environments such as discos,
•
pubs etc., if the outside air is too cold the same problem as described
above occurs.
In these cases, to speed up the correction, the heating coil needs to be
activated by the outlet probe.
Depending on the heating devices used, the following actions are
implemented:
Heating valve:
1.
when the outlet temperature falls below the minimum
outlet temperature (TMm), MasterAria starts opening the heating
valve until opening completely at the value of (TMm-Diff ).
Modulating heater only:
2.
same operation as for the modulating
valve.
ON/OFF heater only:
3.
as shown in the graph, if the only heating device
is the ON/OFF heater, then it switches on at (TMm - Diff ).
ON
OFF
100%
0%
TM
TMm
TMm - Diff
t
t
t
VC/RM
R
Fig. 4.t
Key
t
time
TM
outlet temperature
VC/RM
mod. heating valve/
heater
TMm
min outlet temp. (P106)
R
ON/OFF heater
Diff
outlet limit diff . (P126)
Par
Description
Def1
Def2 Def3 Min Max
UOM
106
Minimum cooling valve/
heating valve-heater
outlet temperature
127(*)
18
18
-28
127
°C
126
Outlet limit diff erential
20
20
20
10
255
°C/10
Tab. 4.j
(*) 127 = function disabled
Maximum outlet limit
This limit is implemented when the AHU is working in heating mode and
due to sudden variations in the outside environmental conditions or faults
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