27VNA3 Infinity® Variable Speed Heat Pump: Installation Instructions
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19
Troubleshooting
Systems Communication Failure
If communication with the Infinity® System Control is lost, the control
will flash the appropriate fault code (see Table 11). Check the wiring to
the Infinity® System Control and the indoor and outdoor units and
power.
Model Plug
The system PCM has been pre-programmed with an electronic model
plug that establishes the model configuration, i.e. size and type, of the
unit. This electronic model plug removes the need for a physical model
plug to be installed into the PCM. A set of physical model plugs for all
sizes is available as a service component for use when replacing the
PCM and/or the model configuration is missing or unknown.
Additionally, the model configuration can be set using the Infinity®
System Control, the Service Tech App, or the PCM dip switches. The
correct model configuration must be set for the system to operate
properly. (see Table 7). Refer to the Service Manual for more
information on model configurations.
NOTE: Model configuration diagnostics will occur while the equipment
is operating, but changes to a model configuration using a physical
model plug will not affect equipment operation until power is cycled. An
electronically set model configuration will take effect immediately. The
PCM remembers the most recent valid model configuration detected at
power-up, regardless of that configuration coming from an electronic or
physical model plug. Model configuration memory is preserved across
power cycles, so proper equipment operation will continue even if power
to the equipment is lost and then restored. An installed model plug at
power-up takes precedence over a model configuration value stored in
memory. If a new valid model plug value is detected at power-up, the
model configuration memory will be updated to that new value.
Pressure Switch Protection
The outdoor unit is equipped with high pressure switch. If this switch
opens the VFD will lose line power and the compressor and fan motor
will not operate. The high pressure switch opens at 670 +/- 10 psig and
closes at 470 +/- 25 psig. If this occurs the PCM will set a diagnostic
code per Table 11. The outdoor pressure transducer installed at the
discharge of the compressor is monitored by the PCM and the PCM will
take action to avoid the high pressure switch from opening.
Compressor Protection
The Primary Control Module continuously monitors the operation of the
compressor and takes action when it is nearing the edge of the
boundaries of reliable operation. The PCM utilizes the pressure
transducers to maximize the reliability and minimize the off time of the
system due to operation outside of the compressor boundaries. The PCM
takes different actions for each edge of the boundary, but each
culminates in a reduction of compressor speed to the minimum
allowable and, in the worst case, will power off the compressor to avoid
excursions outside the boundaries. If a shutdown does occur then the
PCM will set a diagnostic code per Table 11.
Line Voltage Diagnostics
The primary control module monitors the line voltage for low and high
voltage events. If a low voltage or high voltage event occurs and another
fault occurs simultaneously the PCM will set a fault that indicates this
was due to the system conditions and not the components. If this occurs
several times in a row the PCM will set a malfunction and lock out
operation for 1-4 hours, depending on the condition. Refer to Table 11
for the list of fault codes and Table 12 for the list of malfunctions and the
lockout times for each one.
Forced Defrost Pins
The forced defrost pins have several functions. When shorting the pins
using a clip wire the below functions can be executed:
If the pins are shorted for more than 5 seconds and the unit is in heating
mode, the unit will enter into a defrost.
If the pins are shorted more than 1 second and less than 5 seconds when
the system has just turned off and an active call for cooling or heating is
present, the 5 minute initial on-time will be defeated.
If the unit is in the OFF mode and the pins are shorted at power on the
unit will enter into Status Code Recall Mode.
Temperature Thermistors
Thermistors are used to sense the outdoor ambient (OAT), outdoor coil
(OCT-HP), liquid line (LLT-HP), any outdoor discharge (ODT) line
temperatures. All thermistors are 10K thermistors except for the ODT,
which is a 50k thermistor.
Refer to Table 8 and Table 9 for resistance values versus temperature for
the OAT, OCT - HP, ODT, and LLT - HP.
If the outdoor air or coil thermistor should fail, the control will flash the
appropriate fault code (see Table 11.)
IMPORTANT: The OAT, OCT/LLT, OST, and ODT thermistors should
be factory mounted in the final locations. Check to ensure thermistors
are mounted properly (See Fig. 33, Fig. 34 and Fig. 35).
Outdoor Air Temperature (OAT)
The OAT is a 10K thermistor used for multiple system operations. It
provides the outdoor air temperature to the primary control module and
Infinity® System Control. It is essential for controlling the system and is
used in almost all modes of operation. The sensor is mounted in the
control box per Fig. 33. See Table 8 for proper resistances.
Table 7 – Model Plug Information
MODEL
NUMBER
MODEL PLUG
NUMBER
PIN RESISTANCE
(K-ohms)
PCM Model
Pins 1-4 Pins 2-3 HP
27VNA336 HK70EZ015 5.1K 360K 36K-HP
27VNA348 HK70EZ027 11K 150K 48K-HP
27VNA360 HK70EZ039 18K 62K 60K-HP
CAUTION
!
EQUIPMENT DAMAGE HAZARD
Failure to follow this caution may result in equipment damage and/or
improper operation.
Do not attempt to install an incorrect model plug as this could cause
some units to operate incorrectly and fail prematurely.
Table 8 – 10K Thermistor Resistance Values
TEMPERATURE RESISTANCE (K OHMS)
25.0°C (77.0°F) 10.0 + / - 2.3%
0.0°C (32.0°F) 32.6 + / - 3.2%
-17.8°C (0 °F) 85.5 + / - 3.4%
Table 9 – 50K Thermistor Resistance Values
TEMPERATURE (°C) RESISTANCE (K OHMS)
25 50.15 + / - 5.0%
75 7.565 + / - 3.0%
125 1.7 + / - 1.4%
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