34
Table 19 — Sensor Resistance Values
3. Quick Test Steps 2.4.-3.3. — Output Relay Check
These quick test steps allow microprocessor to check out-
put signals from relay boards in unit control system. In
addition, operation of all the condenser fans, compres-
sors, and economizer (if equipped) are checked at each
step.
Normal display for Steps 2.4. through 2.8. is 1. In Steps
2.9. through 3.2., each compressor and unloader is started
and allowed to run for approximately 10 seconds. At
startup, a 0 will appear on the display followed by a
1 (Steps 2.9. and 3.2.) in a few seconds. Steps 3.0. and
3.1. will always be 0 since there are unloaders, and Step
3.3. will always be zero since it is not used.
At end of the 10-second time period, a 0 will return to the
display board indicating that test step has been success-
fully completed (Steps 2.9. and 3.2.). The 1 indicates that
was tested.
Fan and compressor operating sequence for quick test
Steps 2.4. through 3.3. are shown in Table 18.
If the quick test steps do not operate as described above, a
defect exists in one or more of the following: relay being test-
ed, electronic control, or unit wiring. Determine problem and
correct.
OPERATING INFORMATIONDigital Display — The VAV control system uses a 2-digit
LED display located on the display board to display operation-
al information and diagnostic codes.
CODES 0 THROUGH 8, CAPACITY STEPS — These codes
indicate the number of cooling stages active at the time the dis-
play button is pressed. The highest code indicated on the dis-
play will be 6 for the 034,038 and 048-088 units, 4 for the 044
units, and 8 for the 104 units.
Capacity steps are directly related to pin terminal connector
J6 output. At step zero, the unit has no mechanical cooling on,
and the economizer may or may not be operating (depending
on the outdoor air conditions). Once a cooling load is detected
(T1 thermistor reads above the supply-air set point), the econo-
mizer will begin modulating to meet the load if the outdoor
enthalpy is good. As long as the outdoor-air enthalpy is accept-
able, no mechanical cooling will take place until the economiz-
er dampers are fully open. The rest of the steps and the opera-
tional sequence vary due to the number of compressors and un-
loaders. Refer to Operating Sequence section on page 35 for
the unit stages of operation.
CODES 20 THROUGH 30 AND 88, OPERATIONAL STA-
TUS — These codes indicate special operational modes, such
as initialization, morning warm-up, temperature reset, demand
limit, or an internal failure of the board. Codes 23-25 and
27-29 are not used on these units.
Initialization — When the control is turned on, the display
shows a 20 for approximately 2 minutes to indicate that the
control is in the initialization mode. During this time, the econ -
omizer dampers open and close to determine the resistance
range of the economizer position potentiometer (P2) for full
economizer operation. The processor loads the necessary con-
stants for proper unit operation and checks the thermistors and
other potentiometers for their values and validity. After the ini-
tialization period, the display screen goes blank until the dis-
play button is pressed. If the display button is pressed during
the 2-minute initialization period, the control goes into the
Quick Test mode.
Temperature Reset — If the unit is equipped with the accesso-
ry temperature reset package, and DIP switch 2 is in the ON
position, the unit will reset the supply-air temperature to a cal-
culated value when necessary. When this condition is in effect,
a 21 will appear in the display.
Demand Limit — If the unit is equipped with the accessory
demand limit control module or the field-supplied, single-step
demand limit potentiometer, and DIP switch 5 is in the ON
position, the unit will limit the capacity stages to a predeter-
mined value. When this condition is in effect, a 22 will appear
in the display.
Morning Warm-Up — If the morning warm-up heat routine is
enabled using DIP switch 4, and conditions of the occupied
space warrant, the unit will begin the morning warm-up rou-
tine. When this condition is in effect, a 26 will appear in the
display.
Internal Failure — If the unit detects an internal fault (such as
a time measurement failure), or detects an incorrect voltage on
an input channel, a 30 will be displayed, and the unit will shut
down.
Quick Test — If the display button is pressed during the ini-
tialization period of the processor, the unit will run its self-diag-
nostic routine. When this is in effect, an 88 will appear in the
display screen.
CODES 51 THROUGH 87, DIAGNOSTIC INFORMATION
— These codes indicate diagnostic information when there is a
unit problem such as a faulty thermistor, potentiometer, or
compressor fault. Refer to Diagnostic Codes section on
page 45 for more details. Codes 53, 54, 57, 58, 61, 62, 65-69,
73, 74, and 77-80 are not used on these units.
Under normal operation, only the stage number is displayed
when the display button is pressed. If a status or overload code
is displayed, the display will rotate every 2 seconds and will
display up to 3 codes. Overload information takes priority over
all other codes. The codes are stored in the microprocessor as
long as the board remains energized.
TEMP
(F)
RESISTANCE
(Ohms)
TEMP
(F)
RESISTANCE
(Ohms)
TEMP
(F)
RESISTANCE
(Ohms)
–60 362,640 45 11,396 150 1,020
–55 297,140 50 9,950 155 929
–50 245,245 55 8,709 160 844
–45 202,841 60 7,642 165 768
–40 168,250 65 6,749 170 699
–35 139,960 70 5,944 175 640
–30 116,820 75 5,249 180 585
–25 98,420 80 4,644 185 535
–20 82,665 85 4,134 190 490
–15 69,685 90 3,671 195 449
–10 58,915 95 3,265 200 414
–550,284 100 2,913 205 380
042,765 105 2,600 210 350
536,475 110 2,336 215 323
10 31,216 115 2,092 220 299
15 26,786 120 1,879 225 276
20 23,164 125 1,689 230 255
25 19,978 130 1,527 235 236
30 17,276 135 1,377 240 219
35 14,980 140 1,244
40 13,085 145 1,126