37
Table 37 — Cool/Heat Setpoint Offsets Configuration
Demand Level Low Cool On Offset
(
L.C.ON
) — This is the
cooling setpoint offset added to the cooling setpoint at which
point a Low Cool mode starts.
Demand Level High Cool On Offset
(
H.C.ON
) — This is the
cooling setpoint offset added to the “cooling setpoint 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 setpoint offset subtracted from “cooling setpoint 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 tempera-
ture must rise above the cooling setpoint plus
L.C.ON
.
To enter into a HIGH COOL mode, the controlling tem-
perature must rise above the cooling setpoint plus
L.C.ON
plus
H.C.ON
.
To exit out of a LOW COOL mode, the controlling tem-
perature must fall below the cooling setpoint plus
L.C.ON
mi-
nus
L.C.OF
.
To exit out of a HIGH COOL mode, the controlling tem-
perature must fall below the cooling setpoint plus
L.C.ON
mi-
nus
L.C.OF
/2.
Comfort Trending
— In addition to the setpoints and offsets
which determine the trip points for bringing on and 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 quickly enough. This method is referred to as
Comfort Trending. The comfort trending configurations 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 period 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 types (
C.TYP
= 5 and 6),
because they may transition into the occupied mode and see an
immediate large cooling demand when the setpoints 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 setpoints and offsets which
determine the trip points for bringing on and off cool modes
there is a timeguard of 8 minutes which enforces a time delay
between the transitioning from a low cool to a high cool mode.
There is a timeguard of 5 minutes which enforces a time delay
between the transitioning from a heat mode to a cool mode.
Supply Air Setpoint Control
—
Once the control has deter-
mined that a cooling mode is in effect, the cooling control
point (
Run Status
VIEW
CL.C.P
) is calculated and is
based upon either
Setpoints
SA.HI
or
Setpoints
SA.LO
,
depending on whether a high or a low cooling mode is in
effect, respectively. In addition, if supply air reset is config-
ured, it will also be added to the cooling control point.
Refer to the SumZ Cooling Algorithm section for a discus-
sion of how the A Series
Comfort
Link controls manage supply-
air temperature and the staging of compressors for these
control types.
Thermostat Cool Mode Selection (
C.TYP
= 3 and 4
) —
When a thermostat type is selected, the decision making pro-
cess involved in determining the mode is straightforward.
Upon energizing the Y1 input only, the unit HVAC mode will
be LOW COOL. Upon the energizing of both Y1 and Y2 in-
puts, 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 the
Configuration
UNIT
SIZE
configuration parameter 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
setpoint to control
to. An HVAC mode equal to HIGH COOL will cause the
unit to select the
Setpoints
SA.HI
setpoint to control to.
Supply air reset (if configured) will be added to either the
low or high cool setpoint.
• The control will utilize the SumZ cooling algorithm and
control cooling to a supply air setpoint. See the SumZ Cool-
ing Algorithm section for information on controlling to a
supply air setpoint and compressor staging.
Selecting the
C.TYP
= 4 (TSTAT – 2 STG) control type
means that only two stages of cooling will be used. On unit
sizes 020, 025 and 027 (with three compressors), an HVAC
Mode of LOW COOL will energize one compressor in Cir-
cuit A; an HVAC Mode of HIGH COOL will energize all
three compressors. On unit sizes 030 and larger (with four
compressors) an HVAC Mode of LOW COOL will energize
both compressors in Circuit A; an HVAC Mode of HIGH
COOL will energize all four compressors. Refer to the sec-
tion on Economizer Integration with Mechanical Cooling
for more information.
2-Stage Cooling Control Logic (
C.TYP
= 4 and 6
) — The
logic that stages mechanical cooling for the TSTAT and SPT
2-Stage cooling control types differs from that of the multi-
stage control types. This section will explain how compressors
are staged and the timing involved for both the Low Cool and
High Cool HVAC Modes.
There are either three or four compressors divided among two
refrigeration circuits. Circuit A always contains two compressors
(
Outputs
COOL
A1
and
A2
). Circuit B has either one com-
pressor (
Outputs
COOL
B1
) on size 020-027 units or two
compressors (
Outputs
COOL
B1
and
B2
) on size 030-060
units. For 2-stage cooling control, regardless of configuration,
there is no minimum load valve (MLV) control. The decision as
to which compressor should be turned on or off next is decided
by the compressor’s availability and the preferred staging order.
Either A1 or A2 may start first as there is a built-in lead/lag
logic on compressors A1 and A2 every time the unit stages to 0
compressors. Also, based on compressor availability, it should
be noted that any compressor may come on. For example, on a
3 compressor unit, if no compressors are currently on,
compressor A2 is currently under a minimum off compressor
ITEM
EXPANSION
RANGE
UNITS
CCN POINT
DEFAULT
D.LV.T
COOL/HEAT SETPT. OFFSETS
L.H.ON
Dmd Level Lo Heat On
-1 - 2
^F
DMDLHON
1.5
H.H.ON
Dmd Level(+) Hi Heat On
0.5 - 20.0
^F
DMDHHON
0.5
L.H.OF
Dmd Level(-) Lo Heat Off
0.5 - 2
^F
DMDLHOFF
1
L.C.ON
Dmd Level Lo Cool On
-1 - 2
^F
DMDLCON
1.5
H.C.ON
Dmd Level(+) Hi Cool On
0.5 - 20.0
^F
DMDHCON
0.5
L.C.OF
Dmd Level(-) Lo Cool Off
0.5 - 2
^F
DMDLCOFF
1
C.T.LV
Cool Trend Demand Level
0.1 - 5
^F
CTRENDLV
0.1
H.T.LV
Heat Trend Demand Level
0.1 - 5
^F
HTRENDLV
0.1
C.T.TM
Cool Trend Time
30 - 600
sec
CTRENDTM
120
H.T.TM
Heat Trend Time
30 - 600
sec
HTRENDTM
120
Содержание Carrier Weathermaker 48A2
Страница 105: ...105 Fig 20 Typical Main Control Box Wiring Schematic 48 50A2 A3 A4 A5 Units...
Страница 106: ...106 Fig 21 Typical Auxiliary Control Box Wiring Schematic...
Страница 107: ...107 Fig 22 Typical 2 Stage Gas Heat Wiring Schematic Size 060 Units Shown a48 8357...
Страница 108: ...108 TO NEXT PAGE Fig 23 Typical Staged Gas Heat Wiring Schematic Size 060 Units Shown A48 7296...
Страница 109: ...109 Fig 23 Typical Staged Gas Heat Wiring Schematic Size 060 Units Shown cont A48 8358...
Страница 110: ...110 Fig 24 Typical Electric Heat Control Schematic 50 Series Size 060 Units Shown a50 8228...
Страница 111: ...111 Fig 25 Typical Power Schematic 48 50A2 A3 A4 A5 060 Unit Shown...
Страница 112: ...112 Fig 26 Typical Low Ambient Controls Option Wiring...
Страница 113: ...113 Fig 27 Typical Small Chassis Component Location Size 020 035 Units...
Страница 114: ...114 Fig 28 Typical Large Chassis Component Locations Size 040 060 Units...
Страница 118: ...118 Fig 30 Economizer Control Board ECB1 and VAV Control Board ECB2 A48 7706...
Страница 142: ...142 A48 3733 Fig 56 Main Burner Removal...
Страница 176: ...176 APPENDIX C VFD INFORMATION cont Fig F Internal Enclosure Fan Replacement A48 7716...
