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51
Operating modes are under
Operating Modes
MODE
.
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 com-
pensated start mode, the occupied cooling set point (
OCSP
) is
used. For all other modes, the unoccupied cooling set point (
UC-
SP
) is used. For further discussion and simplification this will be
referred to as the “cooling set point.” See Fig. 6.
Fig. 6 — 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 a HIGH COOL mode, the controlling tempera-
ture 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
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 section 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 transi-
tioning 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
VIEW
CL.C.P
) is cal-
culated and is based upon either
Setpoints
SA.HI
or
Set-
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
Comfort
Link 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
UNIT
SIZE
and
Configuration
UNIT
50.HZ
configuration
parameters to determine the number of cooling stages and
the pattern for each stage.
• An HVAC mode equal to LOW COOL will cause the unit
to select the
Setpoints
SA.LO
set point to control to. An
HVAC mode equal to HIGH COOL will cause the unit to
select the
Setpoints
SA.HI
set point to control to. Supply
air reset (if configured) will be added to either the low or
high cool set point.
• The control will utilize the SumZ cooling algorithm and
control cooling to a supply air set point. See the SumZ Cool-
ing Algorithm section on page 52 for information on con-
trolling to a supply air set point and compressor staging.
COOL MODE DIAGNOSTIC HELP
To quickly determine the current trip points for the cooling modes,
the Run Status sub-menu at the local display allows the user to
view the calculated start and stop points for both the cooling and
heating trip points. The following sub-menu can be found at the
local display under
Run Status
TRIP
.
See Table 37.
ITEM
EXPANSION
RANGE
CCN POINT
MODE
MODES CONTROLLING UNIT
OCC
Currently Occupied
ON/OFF
MODEOCCP
T.C.ST
Temp.Compensated Start
ON/OFF
MODETCST
H.C.ON
L.C. OF/2
L.C.ON
Cooling Setpoint (OCSP,UCSP)
L.C. OF
Lo Cool End
Hi Cool End
Lo Cool Start
Hi Cool Start
Summary of Contents for Weathermaster 48P2030-100
Page 130: ...130 Fig 19 Typical Power Schematic Sizes 040 075 Shown ...
Page 131: ...131 Fig 20 Main Base Board Input Output Connections ...
Page 132: ...132 Fig 21 RXB EXB CEM SCB Input Output Connections ...
Page 133: ...133 Fig 22 Typical Gas Heat Unit Control Wiring 48P030 100 Units Shown ...
Page 134: ...134 Fig 23 Typical Electric Heat Wiring 50P030 100 Units Shown ...
Page 135: ...135 Fig 24 Typical Power Wiring 115 V ...
Page 136: ...136 Fig 25 Typical Gas Heat Section Size 030 050 Units Shown ...
Page 138: ...138 Fig 27 Component Arrangement Size 030 035 Units ...
Page 139: ...139 Fig 28 Component Arrangement Size 040 075 Units ...
Page 140: ...140 Fig 29 Component Arrangement Size 090 100 Units ...