Random Start; Compressor Protection; Microprocessor Control Unit Flash Codes; Communication - Johnson Controls VB09 Installation, Operation And Maintenance Manual

SECTION 2 - OPERATION
Installing the jumper bypasses the freeze-stat, enabling
heating operation with a leaving glycol fluid mixture
temperature below 35.0°F. Use the jumper only in low
water applications with adequate antifreeze protection,
otherwise damage can occur.

Random Start

The random start function upon power up imposes
time delay of 4 minutes plus a random delay of 1–64
seconds. A combination of the following determine the
random number generator seed:
• A fixed seed programmed at the factory
• The serial number
• The model number
• The hours of the unit's compressor runtime

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
list of all flash codes, see Table 13 on page 42.
Current alarms or active restrictions are flashed on the
microprocessor control LED.
42
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 13 - FLASH CODES

FLASH CODES
On Steady Control failure – replace control
Heart Beat Normal operation
2 Flashes Control waiting on ASCD
3 Flashes HPS1 - Compressor lockout
5 Flashes LPS1 - Compressor lockout
13 Flashes Compressor held off due to low voltage
EEPROM storage failure (control
14 Flashes
failure)
Condensate overflow switch -
15 Flashes
compressor lockout
Coaxial freeze thermostat -
16 Flashes
compressor lockout
NOTES
1. These flash codes do not represent alarms.

Communication

The communication protocol is Modbus
RTU method of packet framing at 19200-baud rate.
FORM 145.18-IOM1
ISSUE DATE: 8/30/2018
DESCRIPTION
1
1
using the
™