71
TROUBLESHOOTING
By using the accessory keypad and display module and the
status function, actual operating conditions of the unit are dis-
played while it is running. Test function allows proper opera-
tion of compressors, compressor unloaders, fans, and other
components to be checked while unit is stopped. Service func-
tion displays how configurable items are configured. If an
operating fault is detected, an alarm is generated and an alarm
code(s) is displayed under the subfunction
, along with
an explanation of the fault. All current alarm codes are
stored under this subfunction. For checking specific items, see
Table 57.
Checking Display Codes —
To determine how the
unit has been programmed to operate, check diagnostic infor-
mation (
and ) and operating mode displays
( ). If no display appears, follow procedures in Control
Modules section on page 81. If display is working, continue as
follows:
1. Note all alarm and alert codes displayed, and
.
2. Note all operating mode codes displayed, .
3. Note control temperature set point in effect and current
control temperature, .
If unit is running, compare the “in effect” control set
point with current temperature. Check the program-
ming of schedule function to see if occupied or unoc-
cupied set point should be in effect.
Unit Standby —
To place the unit in Standby mode, place
LOCAL/REMOTE selection switch in the LOCAL (OFF) po-
sition and then use the HSIO and press . Press
until the display reads STBY YES or STBY NO. If display
reads STBY NO, press to place the unit in Standby
mode. If display reads STBY YES, the unit is already in the
Standby mode. To remove the unit from Standby mode, press
.
Any compressors and condenser fans which are operating
will take several seconds to shut down once the unit is placed
in Standby mode. The evaporator fan will take approximately
15 seconds to shut down.
NOTE: When unit is in Standby mode (display reads STBY
YES), no commands will be accepted from the CCN commu-
nications bus.
Complete Unit Stoppage —
If the unit is off, there are
several conditions that can cause this situation to occur:
1. Cooling load satisfied.
2. Programmed schedule.
3. General power failure.
4. Blown fuse in the control power feed.
5. Open control circuit fuse.
6. Unit ON/OFF switch moved to OFF position.
7. Loss of communications between the processor mod-
ule and other control modules.
8. Operation of the unit blocked by the demand limit
function.
9. Unit is in Standby mode.
10. Unit is turned off through the CCN network.
11. Unit supply-air temperature (SAT) thermistor failure.
12. Supply-air fan is not operating.
13. High duct static pressure.
14. Remote on-off circuit open (off).
Table 57 — Controls Troubleshooting
*Simultaneous operation of cooling and heating may occur on VAV units as the Occupied Heating function begins.
Check the unit operating mode.
Simultaneous operation of cooling and heating is permitted during Dehumidification/Reheat. Check unit operating mode.
ENTER
SYMPTOM(S) PROBABLE CAUSE(S) SOLUTION(S)
Evaporator fan does not run.
1. Circuit breaker open.
2. Fan configured for automatic
operation.
3. Inverter overload.
1. Find cause and reset circuit breaker.
2. Reconfigure Evaporator Fan from Automatic to Constant
using on HSIO.
3. Find cause and reset.
Compressor does not run.
1. Fan interlock does not sense
evaporator fan is operating.
2. Circuit breaker is open.
3. There is no demand for cooling.
4. The control is locking out cooling
operation.
1. Check fan status switch and pressure tubing.
2. Find cause and reset circuit breaker.
3. Correct operation.
4. Check rotating display for alarm codes. Resolve alarm
cause and reset control by changing to Standby and back
to Run mode.
Condenser fans do not turn on.
1. Unit is equipped with transducers
and service valves are back seated.
2. Circuit breaker is open.
1. Turn service valve at least one turn from backseated
position.
2. Find cause and reset circuit breaker
Heating and cooling occur
simultaneously.*
Occupied heating is configured as on
and occupied heat set point is set higher
than the cooling set point.
Turn off occupied heating, or lower heating set point.
Evaporator fan runs, but
cooling or heating will not
operate.
Fan interlock does not sense that
evaporator fan is operating.
Check fan status switch and pressure tubing.
Economizer does not appear to
control to the discharge air set
point.
Economizer is probably working
correctly.
Economizer controls to a modified set point to maximize free
cooling. See Economizer section on page 20.
Cooling demand exists and
economizer modulates, but
compression is not operating.
Compression cannot be initiated until
economizer damper is 90% open.
Correct operation.
Controls do not seem to be
operating.
Remote on-off function may be keeping
controls off.
Terminals 1 and 2 on Channel 49 must be shorted by remote
switch or jumper.
To Next Page
Loading...