15
Marvair GAA A/C w/Gas Heat I&O Manual
06/2023 Rev.5
the Dehum speed is 80% of maximum speed. The speed may be adjusted from 60-100% in 1%
increments to meet desired airflow requirements.
18. DS Calibration:
This setting is used to calibrate the defrost sensor from 0 to -18F.
19. SAS Calibration:
This setting is used to calibrate the supply air sensor from 0 to -18F.
20. T’STAT Select:
The thermostat type can be selected with this setting for an option of H=
Hardwired 24vac Thermostat or C = Communicating Thermostat via Modbus. The default setting
is H= Hardwired 24vac Thermostat.
21. Modbus ID:
This setting allows the Modbus ID to be entered for Modbus communications for
the unit. The range for the Modbus ID is 1 – 36161 the default Modbus ID is 1.
22. Modbus Baud Rate:
This setting allows the Modbus Baud Rate to be entered for Modbus
communications. The available Baud Rates are 9.6= 9600 and 19= 19200. The default Modbus
Baud Rate is 19 = 19200.
23. Modbus Timeout:
This is the setting for the Modbus communications timeout in minutes. The
range of communications timeout is from 25 minutes to 21916 minutes. The default communications
timeout is 25 minutes.
24. Test:
The Test feature has two options Y= Yes or N= No. When this setting is set to Y=Yes, all
circuit timers are reduced to expedite testing for various system operations. When set to N=No,
all circuit timers are used in their default configuration and normal operation.
25. Software Version Number:
The software version of the 92589-control board will be displayed
on the seven-segment display. This is for informational purposes only.
2.4 Operation
Power
The Marvair PCB requires 24 VAC to operate. When the board is sufficiently powered, the “
PWR
” status
light on the PCB illuminates “Green.” When the power supply voltage is 16vac or less for 10 seconds the
control board will de-energize all outputs. This is considered a voltage brownout (low voltage) condition
and the display of the control board will show “03” as an indicator of brownout (low voltage). When
the voltage rises back to 17 VAC, the control board will allow the system to operate.
Note:
The nominal power supply for the control board is 24 VAC and this voltage should be confirmed
during startup to assure normal operation.
Communication
The Marvair PCB comes equipped the Modbus communications standard. There are 2 adjacent RJ11
Modbus communication ports connected in parallel. That is, both ports transmit the same information.
The board allows you to set the Baud Rate at 9600 bits per second or 19200 bits per second. The board
also allows the Modbus ID to be selected in the configuration menu with the available range from 1 to
36161. The default Modbus ID is 1.
See section 2.1 for reference.
2.5 Sequence of Operation
IMPORTANT
All equipment should go through the recommended commissioning/start up sequence
to ensure safety and system reliability. This document is only valid if the system is
used as intended.
This section defines the manner and method of control of the HVAC system. It will cover the
following operations and protections.
