54
Where:
Z.GN
= configuration used to modify the threshold levels used
for staging (
Configuration
COOL
Z.GN
)
ADD.R
=
R.PCT
*
(
C.CAP
– capacity after adding a cooling
stage)
SUB.R
=
R.PCT
* (
C.CAP
– capacity after subtracting a cool
-
ing stage)
Both of these terms,
Z.PLU
and
Z.MIN
,
represent a threshold
both positive and negative, upon which the “SUM” calculation
must build up to in order to cause the compressor to stage up or
down.
Comparing SUM and Z
— The “SUM” calculation is com
-
pared against
Z.PLU
and
Z.MIN
.
• If “SUM” rises above
Z.PLU
, a cooling stage is added.
• If “SUM” falls below
Z.MIN
, a cooling stage is subtracted.
There is a variable called
SMZ
that can simplify the task of
watching the demand build up or down over time. It is calculat
-
ed as follows:
If SUM is positive:
SMZ
= 100*(SUM/
Z.PLU
)
If SUM is negative:
SMZ
= 100*(SUM/
Z.MIN
)
Mixed Air Temperature Calculation (MAT)
The mixed-air temperature is calculated and is a function of the
economizer position. Additionally, there are some calculations
in the control which can zero in over time on the relationship of
return and outside air as a function of economizer position.
There are 2 configurations which relate to the calculation of
“MAT.” These configurations can be located at the local dis
-
play under
Configuration
UNIT
.
MAT Calc Config
(
MAT.S
)
—
This configuration gives the
user 3 options in the processing of the mixed-air temperature
(MAT) calculation:
•
MAT.S
= 0
There will be no MAT calculation.
•
MAT.S
= 1
The control will attempt to learn MAT over time. Any time
the system is in a vent mode and the economizer stays at a
particular position for long enough, MAT = EDT. Using
this, the control has an internal table whereby it can more
closely determine the true MAT value.
•
MAT.S
= 2
The control will stop learning and use whatever the control
has already learned. Using this setting infers that the con
-
trol has spent some time set to
MAT.S
= 1.
First set
MAT.S
= 1. Then go into the Service Test mode, turn
on the fan, and open the economizer to a static position for 5
minutes. Move to several positions (20%,40%,60%,80%). It is
important that the difference between return and outside tem
-
perature be greater than 5 degrees. (The greater the delta, the
better). When done, set
MAT.S
= 2, and the system has been
commissioned.
Reset MAT Table Entries?
(
MAT.R
)
—
This configuration al
-
lows the user to reset the internally stored MAT learned config
-
uration data back to the default values. The defaults are set to a
linear relationship between the economizer damper position
and OAT and RAT in the calculation of MAT.
SumZ Overrides
There are a number of overrides to the SumZ algorithm which
may add or subtract stages of cooling.
• High Temp Cap Override (
H.TMP
)
• Low Temp Cap Override (
L.TMP
)
• Pull Down Cap Override (
PULL
)
• Slow Change Cap Override (
SLOW
)
Economizer Trim Override
The unit may drop stages of cooling when the economizer is per
-
forming free cooling and the configuration
Configura
-
tion
ECON
E.TRM
is set to Yes. The economizer controls to
the same supply air set point as mechanical cooling does for SumZ
when
E.TRM
= Yes. This allows for much tighter temperature
control as well as cutting down on the cycling of compressors.
For a long cooling session where the outside-air temperature
may drop over time, there may be a point at which the econo
-
mizer has closed down far enough where the unit could remove
a cooling stage and open up the economizer further to make up
the difference.
Mechanical Cooling Lockout (Configuration
COOL
MC.LO)
This configuration allows a configurable outside-air tempera
-
ture set point below which mechanical cooling will be com
-
pletely locked out.
DEMAND LIMIT CONTROL
Demand Limit Control may override the cooling algorithm and
clamp or shed cooling capacity during run time. The term De
-
mand Limit Control refers to the restriction of the machine ca
-
pacity to control the amount of power that a machine will use.
Demand limit control is intended to interface with an external
Loadshed Device either through CCN communications, exter
-
nal switches, or 4 to 20 mA input.
The control has the capability of loadshedding and limiting in 3
ways:
• Two discrete inputs tied to configurable demand limit set
point percentages.
• An external 4 to 20 mA input that can reset capacity back
linearly to a set point percentage.
• CCN loadshed functionality.
NOTE: It is also possible to force the demand limit variable
(
Run Status
COOL
DEM.L
).
To use Demand Limiting, select the type of demand limiting to
use. This is done with the Demand Limit Select configuration
(
Configuration
BP
DMD.L
DM.L.S
).
To view the current demand limiting currently in effect, look at
Run Status
COOL
DEM.L
.
The configurations associated with demand limiting can be
viewed at the local display at
Configuration
BP
DMD.L
.
See Table 33.
Demand Limit Select (DM.L.S)
This configuration determines the type of demand limiting.
• 0 = NONE — Demand Limiting not configured.
• 1 = 2 SWITCHES — This will enable switch input de
-
mand limiting using the switch inputs connected to the
CEM board. Connections should be made to TB202 termi
-
nals 1, 2, 3, and 4.
• 2 = 4 to 20 mA — This will enable the use of a remote 4 to
20 mA demand limit signal. The CEM module must be
used. The 4 to 20 mA signal must come from an externally
sourced controller and should be connected to TB202 ter
-
minals 10 and 11.
• 3 = CCN LOADSHED — This will allow for loadshed and
red lining through CCN communications.
ITEM
EXPANSION
RANGE
CCN
POINT
DEFAULTS
UNIT
UNIT CONFIGURATION
MAT.S
MAT Calc Config
0 to 2
MAT_SEL
1
MAT.R
Reset MAT Table
Entries?
No/Yes MATRESET
No
Содержание WeatherExpert 48N2
Страница 135: ...135 Fig 18 48 50N Typical Power Schematic Nominal 075 Ton Unit Shown ...
Страница 136: ...136 Fig 19 48 50N Typical Power Schematic Nominal Ton 90 150 Units Shown ...
Страница 137: ...137 Fig 20 48 50N Main Base Board Input Output Connections ...
Страница 138: ...138 Fig 21 48 50N RXB EXB CEM Input Output Connections a48 9307 ...
Страница 139: ...139 Fig 22 48 50N EXV SCB Input Output Connections a48 9308 ...
Страница 140: ...140 Fig 23 48N Typical Modulating Gas Heat Unit Control Wiring ...
Страница 141: ...141 Fig 24 50N Typical Electric Heat Unit Control Wiring ...
Страница 144: ...144 Fig 27 48N Typical Gas Heat Section Wiring Nominal Ton 120 to 150 Units ...
Страница 145: ...145 Fig 28 48 50N Typical Power Component Control Wiring 460 v ...
Страница 146: ...146 Fig 29 48 50N Component Control Wiring 575 v Nominal Ton 075 to 150 Units ...
Страница 147: ...147 Fig 30 48 50N Component Arrangement Power Box ...
Страница 148: ...148 Fig 31 48 50N Component Arrangement Control Box ...
Страница 168: ...168 Fig 47 Sensor and Ignition Position Fig 48 Combustion Blower Details SENSOR DETAILS IGNITION DETAILS ...
Страница 240: ...240 APPENDIX D VFD INFORMATION CONT Fig G VFD Bypass Wiring Diagram WHEN USED ...
