Carrier WEATHERMAKER 48J Started Manual page 40

temperature (OAT) r ises a bove 7 5For the highest active cir-
cuitsaturated condensing temperature (SCT) r ises above t he
HPSP a nd remains onuntil t hecondition isrepaired regardless
ofthe OAT and SCT values.
Any time the alert o ccurs, astrike i scalled o utontheaffect-
edcompressor. If three s uccessive strikes occur the compressor
will belocked o utrequiring a manual reset orpower r eset of
the circuit board. The clearing ofstrikes during c ompressor op-
eration i sacombination of3complete cycles or15continuous
minutes ofruntflne operation. If there a re one ortwostrikes on
thecompressor andthree short c ycles ( ON-OFF, ON-OFF,
ON-OFF) less t han 15minutes each o ccur, thestrikes are reset
tozero fortheaffected compressor. If thecompressor turns o n
and runs for15minutes straight withnocompressor failure, the
compressor strikes are cleared.
Additionally, some unitscontain C opeland compressors
equipped withadvanced scroll temperature protection (ASTP).
A label l ocated a bove t heterminal boxidentifies Copeland
Scroll c ompressor models t hatcontain t histechnology. See
Fig.5.Advanced scroll temperature protection isaform ofin-
ternal discharge temperature protection that u nloads thescroll
compressor when theinternal temperature reaches approxi-
mately 3 00E At thistemperature, aninternal bi-metal disk
valve opens and causes thescroll elements toseparate, which
stops compression. Suction a nddischarge pressures balance
while themotor c ontinues torun.The longer thecompressor
runs unloaded, the longer it must cool b efore t hebi-metal disk
resets. See Fig.6.
Tomanually reset ASTR the compressor should b estopped
and allowed tocool. If the compressor isnot s topped, the motor
Fig. 5 -- Advanced Scroll Temperature
Protection Label
120
110 J
too .-_
- 90
.__ _. 80
_g 50 /
4o ._-J
30 /
20/
to
0
0 10 20 30 40 50 60 70 80 90
Compressor Unloaded Run Time (Minutes)
*Times are approximate.
NOTE: Various factors, including high humidity, high ambient tem-
perature, and the presence of a sound blanket will increase cool-
down times.
Fig. 6 -- Recommended Minimum Cool-Down
Time After Compressor is Stopped*
will run until the motor protector trips, which occurs up to
90 minutes later. Advanced scroll temperature protection will
reset automatically before the motor protector resets, which
may take up to 2 hours.
COMPRESSOR TIME GUARDS -- The control will not al-
low any output relay to come on within 3 seconds of any other
output relay. For outputs connected to the compressors, the con-
trol will use a Compressor Minimum OFF Thne of 2 minutes, a
Compressor Minhnum ON Thne of 3 minutes and a Minhnum
Delay before turning on another compressor of 10 seconds.
COOL MODE SELECTION PROCESS -- The A Series
(_nfortLink
TM
controls offer three distinct methods by which
it may select a cooling mode.
1. Thermostat (4:TYP=-3 and 4): The thermostat does not
depend upon the state of occupancy and the modes are
called out directly by the discrete inputs from the thermo-
stat (Inputs-cSTAT-cY1 and Y2).
2. Occupied VAV cooling types ((: TYP=-I and 2) are called
out in the occupied period (Operating Modes--€
MODE-+ OCC=ON).
3. Unoccupied VAV cooling types (4:TYP=-I and 2) are
called out in the unoccupied period (Operating Modes--€
MODE--cOCC=OFF). They are also used for space
sensor control types (4:TYP=-5 and 6) in both the occu-
pied and unoccupied periods.
This section is devoted to the process of cooling mode
determination for the three types outlined above.
VAV Cool Mode Selection during the Occupied Period
(4: TYP = 1,2 and Operating Modes-cMODE _OCC =ON)
-- There is no difference in the selection of a cooling mode for
either VAV-RAT or VAV-SPT in the occupied period. The actual
selection of a cool mode, for both control types, is based upon
the controlling return-air temperature (Temperatures-+AIR. T
_TRL-+R.TMP). Typically this is the same as the return air
temperature thermistor (Temperatures---)AIR. T---_RAI) except
when under CCN Linkage.
VAV Occupied (_ol Mode Evaluation (_nfiguration -- There
are VAV occupied cooling offsets under Seq_oints.
ITEM EXPANSION RANGE UNITS CCNPOINT DEFAULT
V.C.ON VAV Occ. 0-25 deltaF VAVOCON 3.5
Cool On Delta
VC.OF VAV Occ. 1-25 deltaF VAVOCOFF 2
Cool Off Delta
(_ol Mode Determination -- If the machine control type
(Configuration--€ UNIT_: TYP) = 1 (VAV-RAT) or 2 (VAV-
SPT) and the control is occupied (Operating Modes
-+MODE-cOCC=ON), then the unit will not follow the occu-
pied cooling set point (OCSP). Instead, the control will follow
two offsets in the determination of an occupied VAV cooling
mode (Setpoints -+V..C.ON and Setpoints--cV.. C OF), applying
them to the low-heat offtrip point and comparing the resulting
temperature to the return-air temperature.
The Setpoints--cV.C.ON (VAV cool mode on offset) and
Setpoints-cV.C.OF (VAV cool mode off offset) offsets are
used in coniunction with the low heat mode off trip point to
determine when to bring cooling on and off and in enforcing a
true "vent" mode between heating and cooling. See Fig. 7. The
occupied cooling set point is not used in the determination of
the cool mode. The occupied cooling set point is used for
supply air reset only.
m m
OHSP _ _ V.C. ON IV.C. OF
Fig. 7 -- VAV Occupied Period Trip Logic
4O