Hussmann Proto-Aire Installation Manual page 114

Step A9 At this point, it is assumed that the electronic control board is in switchback
(see page 6-6 for details describing switchback). If the compressor you are
trying to turn ON is not wired to the switchback control circuit (refer to the
supplied customized wiring diagram), you will need to investigate the cause
of this switchback condition and correct the existing problem.
Step A10 If the compressor you are trying to turn ON is wired into the switchback
control circuit, use a digital voltmeter and determine where the circuit is
being broken. The switchback control circuit originates from the phase
monitor, passes through the switchback relay on the control board, through
the low pressure mechanical backup switch, then back through the control
board relay and fuse, through the high pressure safety switch, the discharge
line thermostat and finally through the electronic oil level control safety.
Problem B: Evaporator is not defrosting.
Step B1 Visually observe if the Alarm Relay LED on the control board is ON. If
LED is ON, got to step B2. If LED is OFF, refer to the Troubleshooting
Alarms section of this document.
Step B2 Verify that the Clock contained in the Protocol is keeping time. Access and
select the Set the Clock submenu. If the clock is running, go to step B3. If
the clock is not running, try changing the time to the correct setting. You
may want to consult the section on Electrical Noise contained within this
manual.
Step B3 Enter the defrost circuit number you wish to turn ON and activate it. Now
exit and go to the Defrost Menu. Observe the circuit you forced into
defrost. If the status indicates defrost proceed to Step B4. If the status does
not indicate defrost, go to Step B7.
Step B4 Visually observe which defrost relay located on the defrost board is
energized. The corresponding indicator light on the defrost board should be
ON. If the indicator light is ON, proceed to Step B5. If the indicator light is
OFF, proceed to Step B10.
Step B5 At this point, we have assumed that the control is responding correctly and
the problem lies within the control panel. Use a digital voltmeter to check
that voltage is present at the correct terminal blocks in the power
distribution box. You will need to refer to the supplied customized wiring
diagram to determine which terminal blocks are providing power for the
particular case load you are defrosting. If voltage is present at the terminal
blocks, verify that the case is in defrost by visual inspection and then return
to Step B6. If voltage is not present at the terminal blocks, go to Step B11.
Step B6 If the status of this defrost circuit indicates it is deactivated, reactivate the
circuit and verify the programming of this circuit as outlined in controller
manual. If the status of this defrost circuit indicates that it is not installed,
Protocol™ Installation and
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Service Manual