45
SECTION 2 - OPERATION
FORM 145.18-IOM2
ISSUE DATE: 06/17/2020
2
Compressor Protection
In addition to the external pressure switches, the com-
pressor also has inherent internal protection. If there
is an abnormal temperature rise in a compressor, the
protector opens to shut down the compressor. The mi-
croprocessor control incorporates features to minimize
compressor wear and damage. The control uses an
ASCD to prevent compressor operation too soon af-
ter its previous run. Additionally, a minimum runtime
is imposed any time a compressor is energized. The
ASCD initiates on unit start-up and on any compressor
reset or lockout.
Microprocessor Control Unit Flash Codes
The microprocessor control uses various flash codes
to aid in troubleshooting. The flash codes are distin-
guished by a short on and off cycle (approximately
200ms on and 200ms off).
During normal operation, to show that the micropro-
cessor correctly functions, the control boards flash for
1 second on, 1 second off, also known as a heart beat.
Do not confuse this with an error flash code. To pre-
vent confusion, a 1-flash fault code is not used. For a
Current alarms or active restrictions are flashed on the
microprocessor control LED.
Last Error
When this button is pressed and released one time
within 5 seconds, it flashes the last five fault codes on
the board’s LED. The most recent alarm is shown first
and the oldest alarm is shown last.
Test Reset
When this button is pressed and released one time
within 5 seconds, any ASCD is bypassed for one cycle.
Comm Setup
If the board is to be networked with other units, this
button is used to set the network address.
The first time the button is pressed within 5 seconds, it
scans the bus, assigns itself the first available address
(starts at 2), and then flashes that address once.
Pressing the button two times within 5 seconds causes
the control to flash the address.
TABLE 9 -
FLASH CODES
FLASH
CODES
DESCRIPTION
On Steady
Control failure – replace control
Heart Beat
Normal operation
2 Flashes
Control waiting on ASCD
1
3 Flashes
HPS1 - Compressor lockout
5 Flashes
LPS1 - Compressor lockout
11 Flashes
Compressor held off due to
economizer active
1, 2
13 Flashes
Compressor held off due to low voltage
1
14 Flashes
EEPROM storage failure (control
failure)
15 Flashes
Condensate overflow switch -
compressor lockout
16 Flashes
Coaxial freeze thermostat -
compressor lockout
NOTES
1.
These flash codes do not represent alarms.
2. Check for Y1 and ECON jumper on P4.
Communication
The communication protocol is Modbus
™
using the
RTU method of packet framing at 19200-baud rate.
