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ITEM
D.LV.T
COOL/HEAT SETPT. OFFSETS
L.H.ON
Dmd Level
H.H.ON
Dmd Level(+) Hi Heat On
L.H.OF
Dmd Level(-) Lo Heat Off
L.C.ON
Dmd Level
H.C.ON
Dmd Level(+) Hi Cool On
L.C.OF
Dmd Level(-) Lo Cool Off
C.T.LV
Cool Trend Demand Level
H.T.LV
Heat Trend Demand Level
C.T.TM
Cool Trend Time
H.T.TM
Heat Trend Time
Operating modes are under Operating Modes
ITEM
EXPANSION
MODE
MODES CONTROLLING UNIT
OCC
Currently Occupied
T.C.ST Temp.Compensated Start
Cool Mode Evaluation Logic
The first thing the control determines is whether the unit is in the
occupied mode (OCC) or is in the temperature compensated start
mode (T.C.ST). If the unit is occupied or in temperature
compensated start mode, the occupied cooling set point (OCSP)
is used. For all other modes, the unoccupied cooling set point
(UCSP) is used. For further discussion and simplification this
will be referred to as the "cooling set point." See Fig. 5.
H.C.ON
L.C. OF
L.C. OF/2
L.C.ON
Lo Cool End
Cooling Setpoint (OCSP,UCSP)
Fig. 5 — Cool Mode Evaluation
Demand Level Low Cool On Offset (L.C.ON)
This is the cooling set point offset added to the cooling set point, at
which point a Low Cool mode starts.
Demand Level High Cool On Offset (H.C.ON)
This is the cooling set point offset added to the "cooling set point
plus L.C.ON," at which point a High Cool mode begins.
Demand Level Low Cool Off Offset (L.C.OF)
This is the cooling set point offset subtracted from "cooling set
point plus L.C.ON," at which point a Low Cool mode ends.
NOTE: The "high cool end" trip point uses the "low cool off"
(L.C.OF) offset divided by 2.
To enter into a LOW COOL mode, the controlling temperature
must rise above [the cooling set point plus L.C.ON.]
To enter into a HIGH COOL mode, the controlling temperature
must rise above [the cooling set point plus L.C.ON plus H.C.ON.]
To exit out of a LOW COOL mode, the controlling temperature
must fall below [the cooling set point plus L.C.ON minus
L.C.OF.]
To exit out of HIGH COOL mode, controlling temperature must
fall below [the cooling set point plus L.C.ON minus L.C.OF/2.]
Comfort Trending
In addition to the set points and offsets which determine the trip
points for bringing on and bringing off cool modes, there are 2
Table 38 — Cool/Heat Set Point Offsets Configuration
EXPANSION
Lo Heat On
Lo Cool On
MODE.
RANGE
CCN POINT
ON/OFF
MODEOCCP
ON/OFF
MODETCST
Hi Cool Start
Lo Cool Start
Hi Cool End
RANGE
UNITS
–1 to 2
^F
0.5 to 20.0
^F
0.5 to 2.0
^F
–1 to 2
^F
0.5 to 20.0
^F
0.5 to 2
^F
0.1 to 5
^F
0.1 to 5
^F
30 to 600
sec
30 to 600
sec
configurations which work to hold off the transitioning from a
low cool to a high cool mode if the space is cooling down quick-
ly enough. This technique is referred to as comfort trending and
the configurations of interest are C.T.LV and C.T.TM.
Cool Trend Demand Level (C.T.LV)
This is the change in demand that must occur within the time peri-
od specified by C.T.TM in order to hold off a HIGH COOL mode
regardless of demand. This is not applicable to VAV control types
(C.TYP=1 and 2) in the occupied period. As long as a LOW
COOL mode is making progress in cooling the space, the control
will hold off on the HIGH COOL mode. This is especially true for
the space sensor machine control type (C.TYP) = 4, because the
unit may transition into the occupied mode and see an immediate
large cooling demand when the set points change.
Cool Trend Time (C.T.TM)
This is the time period upon which the cool trend demand level
(C.T.LV) operates and may hold off staging or a HIGH COOL
mode. This is not applicable to VAV control types (C.TYP=1 and
2) in the occupied period. See the Cool Trend Demand Level sec-
tion for more details.
Timeguards
In addition to the set points and offsets which determine the trip
points for bringing on and bringing off cool modes there is a
timeguard which enforces a time delay between the transitioning
from a low cool to a high cool mode. This time delay is 8 minutes.
There is a timeguard which enforces a time delay between the
transitioning from a heat mode to a cool mode. This time delay is
5 minutes.
Supply Air Set Point Control
Once the control has determined that a cooling mode is in effect,
the cooling control point (Run Status
culated and is based upon either Setpoints
points
SA.LO, depending on whether a high or a low cooling
mode is in effect, respectively. In addition, if supply air reset is
configured, it will also be added to the cooling control point.
Refer to the SumZ Cooling Algorithm section for a discussion of
how the P Series ComfortLink controls manage supply-air tem-
perature and the staging of compressors for these control types.
C.TYP = 3 (Thermostat Cool Mode Selection)
When a thermostat type is selected, the decision making process
involved in determining the mode is straightforward. Upon ener-
gizing the Y1 input only, the unit HVAC mode will be LOW
COOL. Upon the energizing of both Y1 and Y2 inputs, the unit
HVAC mode will be HIGH COOL. If just input G is energized,
the unit HVAC mode will be VENT and the supply fan will run.
Selecting the C.TYP = 3 (TSTAT – MULTI) control type will
cause the control to do the following:
•
The control will read both the Configuration
SIZE and Configuration
parameters to determine the number of cooling stages and
the pattern for each stage.
54
CCN POINT
DEFAULT
DMDLHON
1.5
DMDHHON
0.5
DMDLHOFF
1
DMDLCON
1.5
DMDHCON
0.5
DMDLCOFF
1
CTRENDLV
0.1
HTRENDLV
0.1
CTRENDTM
120
HTRENDTM
120
VIEW
CL.C.P) is cal-
SA.HI or Set-
UNIT
50.HZ configuration
UNIT
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