Cool Mode Diagnostic Help - Carrier WeatherExpert 48N2 Controls, Start-Up, Operation, Service And Troubleshooting Instructions

• The control will utilize the SumZ cooling algorithm and
control cooling to a supply air set point. See the section
for the SumZ Cooling Algorithm section for information
on controlling to a supply air set point and compressor
staging.
COOL MODE DIAGNOSTIC HELP — To quickly deter-
mine 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 31.
Table 31 — Run Status Mode Trip Helper
ITEM EXPANSION
TRIP MODE TRIP HELPER
UN.C.S Unoccup. Cool Mode Start
UN.C.E Unoccup. Cool Mode End
OC.C.S Occupied Cool Mode Start
OC.C.E Occupied Cool Mode End
TEMP Ctl.Temp R.TMP,S.TMP or Zone dF
OC.H.E Occupied Heat Mode End
OC.H.S Occupied Heat Mode Start
UN.H.E Unoccup. Heat Mode End
UN.H.S Unoccup. Heat Mode Start
HVAC the current HVAC MODE
The controlling temperature is "TEMP" and is in the middle
of the table for easy reference. The HVAC mode can also be
viewed at the bottom of the table.
For non-linkage applications and VAV control types
(C.TYP = 1 or 2), "TEMP" is the controlling return air temper-
ature (R.TMP). For space sensor control, "TEMP" is the con-
trolling space temperature (S.TMP). For linkage applications,
"TEMP" is zone temperature: AOZT during occupied periods
and AZT during unoccupied periods.
SUMZ COOLING ALGORITHM — The SumZ cooling algo-
rithm is an adaptive PID (proportional, integral, derivative)
which is used by the control whenever more than 2 stages of
cooling are present (C.TYP = 1,2,3, and 4). This section will de-
scribe its operation and define the pertinent parameters. It is gen-
erally not necessary to modify parameters in this section. The
information is presented primarily for reference and may be
helpful for troubleshooting complex operational problems.
The only configuration parameter for the SumZ algorithm is
located at the local
 
tion COOL Z.GN. See Table 29.
Capacity Threshold Adjust (Z.GN) — This configuration af-
fects the cycling rate of the cooling stages by raising or lower-
ing the threshold that capacity must build to in order to add or
subtract a stage of cooling.
The cooling algorithm's run-time variables are located at
the local display under Run Status
Current Running Capacity (C.CAP) — This variable repre-
sents the amount of capacity currently running in percent.
Current Cool Stage (CUR.S) — This variable represents the
cool stage currently running.
Requested Cool Stage (REQ.S) — This variable represents
the requested cool stage. Cooling relay timeguards in place
may prevent the requested cool stage from matching the cur-
rent cool stage.
Maximum Cool Stages (MAX.S) — This variable is the max-
imum number of cooling stages the control is configured for
and capable of controlling.
CCN
UNITS
POINT
dF UCCLSTRT
dF UCCL_END
dF OCCLSTRT
dF OCCL_END
CTRLTEMP
dF OCHT_END
dF OCHTSTRT
dF UCHT_END
dF UCHTSTRT
String
display under Configura-

COOL. See Table 32.
Active Demand Limit (DEM.L) — If demand limit is active,
this variable will represent the amount of capacity that the
control is currently limited to.
Capacity Load Factor (SMZ) — This factor builds up or
down over time and is used as the means of adding or subtract-
ing a cooling stage during run time. It is a normalized represen-
tation of the relationship between "Sum" and "Z". The control
will add a stage when SMZ reaches 100 and decrease a stage
when SMZ equals -100.
Next Stage EDT Decrease (ADD.R) — This variable repre-
sents (if adding a stage of cooling) how much the temperature
should drop in degrees depending on the R.PCT calculation
and exactly 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 repre-
sents (if subtracting a stage of cooling) how much the tempera-
ture should rise in degrees depending on the R.PCT calculation
and exactly 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 sub-
tracting 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 cal-
culation that represents the number of degrees of drop/rise
across the evaporator coil versus percent of current running
capacity.
R.PCT = (MAT – EDT)/ C.CAP
Cap Deadband Subtracting (Y.MIN) — This is a control vari-
able 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
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 mechani-
cal 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 per minute,
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 error is less than
–0.5F per minute, then a mechanical stage will be removed
every 30 seconds. This override is intended to quickly react to
situations where the load is rapidly reduced.
52
 
COOL Z.GN * (–10 + (4*
 
COOL Z.GN * (10 + (4*