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24VNA6 / 25VNA4: Service Manual
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
13
A200252
Fig. 11 – 24VAC Power Distribution Diagram
Communication
If communication with the Infinity Control is lost, this will be indicated
by the Comm light being off. There is no diagnostic fault associated
with this condition. When communication with the Infinity Control is
lost, the equipment will default to the discrete control inputs for
operation. Refer to Control Connection in the Control Sub-System
section for further information.
Equipment Configuration (Model Plug)
Each control board contains a model plug. The model plug is used to
identify the type and size of equipment to the control. The correct model
plug must be installed for the system to operate properly (see
Refer to Equipment Configuration in the Control Features and Operation
section for further information.
High Pressure Switch Protection
The outdoor unit is equipped with a high pressure switch. If the control
senses the opening of a high pressure switch, it will respond as follows:
1. De-energize the VFD.
2. Display the appropriate fault code (See
3. After discharge pressure drops below 425 PSIG, if there is a call for
cooling or heating PCM and VFD will restart system.
4. High pressure switch trips do not escalate to a malfunction. Other
system protections should reduce or stop unit operation before
pressure switch opens.
5. Loose fitting connections or wire breaks will also simulate a high
pressure switch trip if the discharge pressure is high. Otherwise, a
loose fitting or wire break will simulate a VFD communication
error.
6. Rapid increase of discharge pressure may not allow other system
protections to take steps to reduce discharge pressure and may
result in high pressure switch trip.
High Pressure Protection
The equipment monitors the discharge pressure relative to high pressure
limits. High pressure limits are compressor speed and model dependent.
If the control senses a high pressure, it will respond as follows:
– Increase outdoor fan speed and lower compressor speed to preempt
a high pressure shutdown. Note: in cooling outdoor fan and
compressor speeds are changed. In heating, suction superheat and
compressor speeds are reduced.
– The control will attempt to compensate for exceeding high pressure
limits. A shutdown will occur if the system is unable to bring
pressure back below the desired limit. The control will shut the
system down immediately if pressure exceeds 620 psig.
– If a high pressure shutdown occurs, a diagnostic code will be set to
indicate the cause for shutdown.
– If high pressure shutdown occurs, the next operating cycle will
operate at 25% less capacity. Each fault after that will reduce
capacity by an additional 25%. Each hour of operation without a
fault will increase the available capacity by 25%.
– If a high pressure fault occurs twice when system is operating at
minimum capacity, the system will shut down with a 2 hour
lockout.
In the event of a high pressure trip or high pressure lockout, check the
refrigerant for an over charge. If the charge is found to be correct, check
for outdoor coil blockage in cooling. In heating, check the indoor coil for
blockage and indoor fan for proper operation.
Low Pressure Protection
The equipment monitors suction pressure relative to low pressure limits.
Low pressure limits are compressor speed and model dependent. If the
control senses a low pressure, it will respond as follows:
– Lower compressor speed and open EXV (heating only) to maintain
suction pressure.
– The control will attempt to compensate for falling below the low
pressure limit. A shutdown will occur if the system is unable to
bring pressure back above the desired limit. The control will shut
the system down immediately if pressure drops to 15 psig.
– If a low pressure shutdown occurs, a diagnostic code will be set to
indicate the cause for shutdown.
– If a demand persists after the 5-minute compressor protection delay
and the pressure has reached the operation level, then the system
will resume operation.
– If a pressure drops below the instantaneous level four (4) times in 2
hours, then a 2 hour lockout will occur, and the system will display
a malfunction code and communicate lockout status to the Wall
Control.
In the event of a low pressure trip or low pressure lockout, check the
refrigerant for an under charge. If the charge is found to be correct,
check for low indoor airflow in cooling and the outdoor fan for proper
operation in heating and outdoor coil in heating for airflow restrictions.
COMPONENT DIAGNOSTICS
Compressor
This compressor operates with a 3-phase variable frequency, variable
voltage applied to the three fusite terminals. If compressor motor failure
is suspected, check the phase resistances and the resistance between each
phase and ground according to the parameters given in
CAUTION
!
EQUIPMENT DAMAGE HAZARD
Failure to follow this caution may result in equipment damage or
improper operation.
Do not attempt to operate system with incorrect model plug as this
could cause equipment damage.
Table 3 – Model Plug Information
MODEL
NUMBER
MODEL PLUG
NUMBER
PIN RESISTANCE
(K-ohms)
Pins 1-4
Pins 2-3
24VNA624
HK70EZ009
5.1K
91K
24VNA636
HK70EZ021
11K
39K
24VNA648
HK70EZ033
18K
11K
24VNA660
HK70EZ045
18K
220K
25VNA424
HK70EZ003
5.1K
24K
25VNA436
HK70EZ015
5.1K
360K
25VNA448
HK70EZ027
11K
150K
25VNA460
HK70EZ039
18K
62K
TRANS
FORMER
PEV
Bluetooth
£
Module
FUSE1
FUSE2
MAIN PCM POWER
MAIN
FUSE
RVS
LLS
R
C