GVZC20 Service Manual

SERVICING
33
INDOOR UNIT TROUBLESHOOTING FOR TXV APPLICABLE UNIT (MBVC**00AA-1)
NOTE: Upon start up in communicating mode the circuit board may display an “Ec” error. This is an indication that the dip
switches on the control board need to be congured in accordance with the Electric Heating Airow Table. Conguring the
dip switches and resetting power to the unit will clear the error code.
Within the thermostat user menu, CTK04 communicating thermostat will display 20 kW for OFF-OFF-ON dip switch
selection.
TROUBLESHOOTING
ELECTROSTATIC DISCHARGE (ESD) PRECATIONS
NOTE: Discharge body’s static electricity before touching
unit. An electrstaic can adversly a󰀨ect electrical compo-
nents.
Use the following precautions during air handler installation
and servicing to protect the integrated control module from
damage. By putting the air handler, the control, and ther
person at the same electrostatic potentential, these steps
will help avoid exposing the integrated control module to
electrostatic discharge. This procedure is applicable to both
installed and uninstalled (ungrounded) blowers.
1. Disconnect all power to the blower. Do not touch the
integrated control module or any wire connected to the
control prior to discharging your body’s electrostatic
charge to ground.
2. Firmly touch a clean, unpainted, metal surface of the
air handler blower near the control. Any tools held in a
person’s hand during grounding will be discharged.
3. Service integrated control module or connecting wiring
following the discharge process in step 2. Use caution
not to recharge your body with static electricity; (i.e., do
not move or shu󰀪e your feet, do not touch ungrounded
objects, etc.). If you come in contact with an unground-
ed object, repeat step 2 before touching control or wires.
4. Discharge your body to ground before removing a new
control from its container. Follow steps 1 through 3 if
installing the control on a blower. Return any old or new
controls to their containers before touching any un-
grounded object.
DIAGNOSTIC CHART
HIGH VOLTAGE!
T O AVOID PERSONAL INJURY OR DEATH DUE TO
ELECTRICAL SHOCK , DISCONNECT ELECTRICAL POWER
BEFORE PERFORMING ANY SERVICE OR MAINTENANCE .

Refer to the Troubleshooting Chart at the end of this man-
ual for assistance in determining the source of unit opera-
tional problems. The 7 segment LED display will provide
any active fault codes. An arrow printed next to the display
indicates proper orientation (arrow points to top of display).
See following image.
7 Segment
Diagnostic
Display
FAULT RECALL
The integrated control module is equipped with a momen-
tary push-button switch that can be used to display the
last six faults on the 7 segment LED display. The control
must be in Standby Mode (no thermostat inputs) to use the
feature. Depress the push-button for approximately two
seconds. The LED display will then display the six most
recent faults beginning with the most recent fault and decre-
menting to the least recent fault. The faults may be cleared
by depressing the button for greater than ve seconds.
NOTE: Consecutively repeated faults are displayed a max-
imum of three times. Example: A clogged return air lter
causes the air handler’s motor to repeatedly enter a limiting
condition. The control will only store this fault the rst three
consecutive times the fault occurs.
S9
S10
OFF
OFF
OFF
OFFON
ON
ON ON
*
(Factory Setting)
19 kW or
20 kW
Electric Heating Air Flow (*indicates factory setting)
15 kW 10 kW
OFF
OFF
OFF
OFFON
ON
ON ON
8 kW 6 kW 5 kW 3 kW
S11
S9
S10
S11
S9
S10
S11
S9
S10
S11
S9
S10
S11
S9
S10
S11
S9
S10
S11
S9
S10
S11