Carrier Weathermaster 48P030-100 Controls, Start-Up, Operation, Service, And Troubleshooting page 120

ITEM
COOL COOLING INFORMATION
C.CAP Current Running Capacity
CUR.S Current Cool Stage
REQ.S Requested Cool Stage
MAX.S Maximum Cool Stages
DEM.L Active Demand Limit
SUMZ COOL CAP. STAGE CONTROL
SMZ Capacity Load Factor
ADD.R Next Stage EDT Decrease
SUB.R Next Stage EDT Increase
R.PCT Rise Per Percent Capacity
Y.MIN Cap Deadband Subtracting
Y.PLU Cap Deadband Adding
Z.MIN Cap Threshold Subtracting
Z.PLU Cap Threshold Adding
H.TMP High Temp Cap Override
L.TMP Low Temp Cap Override
PULL Pull Down Cap Override
SLOW Slow Change Cap Override
HMZR HUMIDIMIZER
CAPC Humidimizer Capacity
C.EXV Condenser EXV Position
B.EXV Bypass EXV Position
RHV Humidimizer 3-Way Valve
C.CPT Cooling Control Point
EDT Evaporator Discharge Tmp
H.CPT Heating Control Point
LAT Leaving Air Temperature
Next Stage EDT Decrease (ADD.R)
This variable represents (if adding a stage of cooling) how much
the temperature should drop in degrees depending on the R.PCT
calculation and how much additional capacity is to be added.
ADD.R = R.PCT * (C.CAP – capacity after adding a cooling stage)
For example: If R.PCT = 0.2 and the control would be adding
20% cooling capacity by taking the next step up, 0.2 times 20 =
4°F ADD.R
Next Stage EDT Increase (SUB.R)
This variable represents (if subtracting a stage of cooling) how
much the temperature should rise in degrees depending on the
R.PCT calculation and how much capacity is to be subtracted.
SUB.R = R.PCT * (C.CAP – capacity after subtracting a cooling
stage)
For example: If R.PCT = 0.2 and the control would be subtract-
ing 30% capacity by taking the next step down, 0.2 times –30 =
–6°F SUB.R.
Rise Per Percent Capacity (R.PCT)
This is a real time calculation that represents the amount of de-
grees of drop/rise across the evaporator coil versus percent of cur-
rent running capacity.
R.PCT = (MAT – EDT)/C.CAP
Cap Deadband Subtracting (Y.MIN)
This is a control variable used for Low Temp Override (L.TMP)
and Slow Change Override (SLOW).
Y.MIN = –SUB.R*0.4375
Cap Deadband Adding (Y.PLU)
This is a control variable used for High Temp Override (H.TMP)
and Slow Change Override (SLOW).
Y.PLU = –ADD.R*0.4375
Cap Threshold Subtracting (Z.MIN)
This parameter is used in the calculation of SMZ and is calculated
as follows:
Z.MIN = Configuration
(–SUB.R))) * 0.6
Table 99 — Cooling Information Display Table
EXPANSION
 
COOL Z.GN * (–10 + (4*
RANGE UNITS
%
%
–100 to +100
^F
^F
Cap Threshold Adding (Z.PLU)
This parameter is used in the calculation of SMZ and is calculated
as follows:
Z.PLU = Configuration
(–ADD.R))) * 0.6
High Temp Cap Override (H.TMP)
If stages of mechanical cooling are on and the error is greater than
twice Y.PLU, and the rate of change of error is greater than 0.5F,
then a stage of mechanical cooling will be added every 30 sec-
onds. This override is intended to react to situations where the load
rapidly increases.
Low Temp Cap Override (L.TMP)
If the error is less than twice Y.MIN, and the rate of change of er-
ror is less than –0.5F, then a mechanical stage will be removed
every 30 seconds. This override is intended to quickly react to sit-
uations where the load is rapidly reduced.
Pull Down Cap Override (PULL)
If the error from set point is above 4F, and the rate of change is
less than –1F per minute, then pulldown is in effect, and "SUM"
is set to 0. This keeps mechanical cooling stages from being added
when the error is very large, but there is no load in the space. Pull-
down for units is expected to rarely occur, but is included for the
rare situation when it is needed. Most likely pulldown will occur
when mechanical cooling first becomes available shortly after the
control goes into an occupied mode (after a warm unoccupied
mode).
Slow Change Cap Override (SLOW)
With a rooftop unit, the design rise at 100% total unit capacity is
generally around 30F. For a unit with 4 stages, each stage rep-
resents about 7.5F of change to EDT. If stages could reliably be
cycled at very fast rates, the set point could be maintained very
precisely. Since it is not desirable to cycle compressors more
than 6 cycles per hour, slow change override takes care of keep-
ing the PID under control when "relatively" close to set point.
120
CCN POINT WRITE STATUS
CAPTOTAL
COOL_STG
CL_STAGE
CLMAXSTG
DEM_LIM forcible
SMZ
ADDRISE
SUBRISE
RISE_PCT
Y_MINUS
Y_PLUS
Z_MINUS
Z_PLUS
HI_TEMP
LOW_TEMP
PULLDOWN
SLO_CHNG
HMZRCAPC
COND_EXV
BYP_EXV
HUM3WVAL
COOLCPNT
EDT
HEATCPNT
LAT
 
COOL Z.GN * (10 + (4*