Diagnostics
114
RT-SVX34F-EN
T.
Economizer modulates, but
system does not seem to
operate as efficiently as in the
past.
1.
Comparative enthalpy setup, RAS or
RHS failed. System is operating using
Reference enthalpy.
1.
Check the return air sensor (RAS) at connector P10 by disconnecting
P10 from RAT on the ECA. Check for resistance between P10-1 and P10-
2, refer to the Resistance versus Temperature Chart. Replace the sensor
if necessary. Check the return air humidity sensor (RHS) by measuring
the operating current at terminals RAH-1 and RAH-2 on the ECA. Normal
operating current is 4 to 20 milliamps mA.
Note:
The humidity sensors
are polarity sensitive, and will not operate if connected backwards.
2.
Reference enthalpy setup, OHS has
failed. System is operating using dry bulb
control.
2.
Check the outside humidity sensor (OHS) by measuring the operating
current at terminals OAH-1, and OAH-2 on the ECA. Normal operating
current is 4 to 20 milliamps mA.
3.
Comparative enthalpy setup, OHS has
failed. System is operating using dry bulb
control.
3.
Perform #2 above.
U.
Power Exhaust will not
operate.
1.
Exhaust motor has failed.
1.
Check the exhaust fan motor, and replace if necessary.
2.
XFR has failed.
2.
Check the exhaust fan contactor (XFR). Replace if necessary
3.
ECA has failed.
3.
Perform the ECA Test Procedures discussed previously.
4.
XFSP has Failed
4.
Perform the Exhaust Fan Setpoint Test Procedures discussed
previously.
V.
VFD will not operate
properly
1.
RTAM has Failed
1.
Perform the RTAM Test Procedures discussed previously.
2.
VFD has Failure
2.
Check the VFD
3.
Setpoint Failure
3.
Perform the VFD Setpoint Test Procedures discussed previously.
4.
RTOM has Failed
4.
Perform the RTOM Test Procedures discussed previously.
W.
Power Exhaust Fan cycles
ON/OFF
1.
Space Pressure Deadband is too
narrow
1.
Increase the Space Pressure Deadband.
2.
Space Pressure Setpoint is too high/
low
2.
Verify Building Pressure with maximum building exhaust enabled.
Adjust Space Pressure Setpoint accordingly.
Table 83. Troubleshooting
SYMPTOM
PROBABLE CAUSE
RECOMMENDED ACTION
Table 84. Component failure mode
COMPONENT
FAILURE RESPONSE
NORMAL RANGE
DIAGNOSTIC
(OAS) Outdoor Air Sensor
1.
Economizer in minimum
position. Will not modulate.
-55 to 175 F
680K to 1.2K
Heat and cool failure output at RTRM J6-7 to J6-
6 and RTRM J6-8 to J6-6. Heat and cool LED's
blink at ZSM. Check at RTRM connector P8,
between P8-1 & P8-2.
2.
ODM3 will not cycle off (runs
continuously).
-55 to 175 F
680K to 1.2K
Check at RTRM connector P8.
(RAS) Return Air Sensor
Economizer operates using
Reference Enthalpy
0 to 209 F
90K to 7.1K
ECA LED 4 Flashes. Check at ECA connector P1
between P10-1 & P10-2.
(MAS) Supply Air Sensor
Economizer in minimum
position, will not modulate.
0 to 209 F
90K to 7.1K
ECA 8 flashes.
(OHS) Outdoor Humidity Sensor
Uses Dry Bulb operation and
economizes if below 60 F DB.
4 to 20 mA
10 to 90% RH Honeywell
C7600A.
ECA 6 flashes.
Check at ECA OAH-1 and OAH-2 by measuring
current draw.
(RHS) Return Humidity Sensor
Economizer operates using
Reference Enthalpy.
4 to 20 mA
10 to 90% RH Honeywell
C7600A.
Check at ECA ECA 3 flashes. RAH-1 and RAH-2 by
measuring current draw.
Remote Minimum position
Potentiometer
1.
Economizer modulates but
minimum position stays at
zero.
Potentiometer range 50 to 200
Ohms.
*NONE* Check resistance at ECA P and P1 50 to
200 Ohms.
Cooling Setpoint (CSP) for CV or
SZ VAV ZSM slide potentiometer
1.
Uses HSP and CSP CSP=
HSP + 4 F or use RTRM Default
Mode.
100 to 900 Ohms Use ZSM Test
Procedures.
*NONE* Check at terminals 2 and 3 on ZSM
Heating Setpoint (HSP) for CV or
SZ VAV
ZSM slide potentiometer
1.
Uses CSP and HSP HSP=
CSP - 4 F.
100 to 900 Ohms Use ZSM Test
Procedures.
*NONE* Check at terminals 2 and 5 on ZSM.
TDL1, TDL2 or TDL3
(Temperature Discharge Limit)
1.
Comp1, Comp2 or Comp3
will not operate.
Open 230 F +/- 6.5 F
Close 180 F +/- 12.5 F
Normally closed
Cool Failure Output at RTRM J6-8 to J6-6 LED
blinks at ZSM.
