Trane Voyager Commercial Installation, Operation And Maintenance Manual page 139

Table 79. Troubleshooting (continued)
SYMPTOM
M. Low Heat Capacity Intermittent
Heat. (YC's only) CFM runs in LO or HI
speed only, or; may not operate at all
in one speed or the other.
N. No Heat (YC's only) "Fan" selection
switch on the ZSM is in the "AUTO"
position and the fan runs
continuously.
O. No Heat (TE's only) Electric heat
will not operate.
P. Evaporator coil freezes up during
low ambient operation.
Q. Economizer will not operate.
R. Minimum position is at zero, cannot
be adjusted. Economizer still
modulates.
S. Economizer goes to minimum
position, and will not modulate.
RT-SVX34R-EN
PROBABLE CAUSE
CFM has failed.
TCO2 has opened. Heat Failure Indicated.
1. Heater contactor(s) have failed.
2. Heater element temperature limit(s) is open.
3. Wiring or terminal failure.
4. Heater Element(s) has failed.
5. RTRM is defective.
1. System low on refrigerant charge.
2. System low on air flow.
3. Outdoor Air Sensor (OAS) has Failed.
4. Frostat™ has Failed
1. Economizer connector not plugged into unit wiring
harness.
2. Economizer Actuator (ECA) has failed.
3. Wiring or terminal failure.
4. ECA is defective.
1. Remote Minimum position potentiometer has
failed.
2. Minimum position potentiometer has failed.
1. OAS has failed.
2. MAS has failed.
RECOMMENDED ACTION
Check CFM, test LO and HI speed windings.
System Status Failure Diagnostic. Place the unit in
the Heating Test Mode, steps 6 & 7 for constant
volume or step 8 & 9 for variable air volume and
check the complete heating system for failure. Make
necessary repairs or adjustments to the unit.
1. Check for 24 VAC at AH, BH,CH, and DH contactor
coils. If 24 VAC is present on a call for heat, and the
contacts do not close, the contactor has failed.
2. Check line voltage between the element
temperature limit terminals located in heat section.
If line voltage is present, the limit is open. Repair
heating unit, or replace limit(s) as needed.
3. Check for wiring, or terminal failure in control and
power circuit. Repair or replace if necessary.
4. Check element and circuit integrity. Repair or
replace as necessary. Replace open elements.
5. Check RTRM heat outputs. "First stage", locate P2
connector, connected to J2 on the RTRM. Locate wire
65E at terminal P2-9, measure between 65E and
ground. If 24 VAC is present, repeat #3 above. If 24
Vac is not present, the RTRM has failed. "Second
stage", Locate 67B wire at terminal P2-8, measure
between 67B and ground. 24 Vac should be present.
If 24 Vac is not present, the RTRM has failed.
1. Leak check, repair, evacuate, and recharge
system as necessary.
2. Check return air for obstruction or dirty filters.
Check fan wheels, motors, and belts.
3. Check OAS at connector P8 by disconnecting P8
from J8 on the RTRM. Check resistance between P8-1
and P8-2, refer to the Resistance versus
Temperature chart. Replace sensor if necessary.
4. Check Frostat Switch
1. Check connector, and connect if necessary.
2. Verify that 24 VAC is present between ECA
terminals 24 VAC and Common. Place the unit in
econ test mode; economizer actuator should drive
open. In any other unit test mode, economizer
actuator should drive to minimum position. If ECA
does not drive as specified, replace ECA.
3. Check wiring and terminals. Repair or replace if
necessary.
4. Perform the ECA Test Procedures discussed
previously.
1. With the main power off, check the resistance
between terminals P and P1 at the ECA by rotating
the remote minimum position potentiometer knob.
Resistance should be 50 to 200 Ohms.
2. Rotate the onboard minimum position
potentiometer knob. If ECA does not drive to
different minimum position, replace ECA.
1. Check the OAS at connector P8 by disconnecting
P8 from J8 on the RTRM. Check resistance between
P8-1 and P8-2, refer to the Resistance versus
Temperature Chart. Replace sensor if necessary.
2. Check the MAS at connector P23 by disconnecting
P23 from MAT on the ECA. "MAT" is marked on the
actuator. Check for resistance between P23-1 and
P23-2, refer to the Resistance versus Temperature
Chart. Replace sensor if necessary.
D D i i a a g g n n o o s s t t i i c c s s
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