Bryant Evolution Extreme 186CNV Service Manual Download Page 12

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186CNV / 284ANV: Service Manual

Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.

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

Table 6

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

Table 3

Fan

If verification of proper operation is required for the ECM motor used in
this unit, refer to

Fig. 11

and follow these steps:

1. Remove fan harness at VFD
2. Check the resistance between connector pins according to the
expected resistances provided in

Table 4

A200184

Fig. 11 – Fan Motor Connections

Table 2 – Model Plug Information

MODEL

NUMBER