Diagnostics
RT-SVX34F-EN
113
N.
No Heat (YC’s only) “Fan”
selection switch on the ZSM is
in the “AUTO” position and the
fan runs continuously.
TCO2 has opened. Heat Failure Indicated.
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.
O.
No Heat (TE's only) Electric
heat will not operate.
1.
Heater contactor(s) have failed.
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.
Heater element temperature limit(s) is
open.
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.
Wiring or terminal failure.
3.
Check for wiring, or terminal failure in control and power circuit. Repair
or replace if necessary.
4.
Heater Element(s) has failed.
4.
Check element and circuit integrity. Repair or replace as necessary.
Replace open elements.
5.
RTRM is defective.
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.
P.
Evaporator coil freezes up
during low ambient operation.
1.
System low on refrigerant charge.
1.
Leak check, repair, evacuate, and recharge system as necessary.
2.
System low on air flow.
2.
Check return air for obstruction or dirty filters. Check fan wheels,
motors, and belts.
3.
Outdoor Air Sensor (OAS) has Failed.
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.
Frostat™ has Failed
4.
Check Frostat Switch
Q.
Economizer will not
operate.
1.
Economizer connector not plugged
into unit wiring harness.
1.
Check connector, and connect if necessary.
2.
Economizer Actuator (ECA) has failed.
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.
Wiring or terminal failure.
3.
Check wiring and terminals. Repair or replace if necessary.
4.
ECA is defective.
4.
Perform the ECA Test Procedures discussed previously.
R.
Minimum position is at zero,
cannot be adjusted.
Economizer still modulates.
1.
Remote Minimum position
potentiometer has failed.
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.
Minimum position potentiometer has
failed.
2.
Rotate the onboard minimum position potentiometer knob. If ECA
does not drive to different minimum position, replace ECA.
S.
Economizer goes to
minimum position, and will not
modulate.
1.
OAS has failed.
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.
MAS has failed.
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.
Table 83. Troubleshooting
SYMPTOM
PROBABLE CAUSE
RECOMMENDED ACTION
