Orion System Dual Digital Module - Manual (Page 11)

Technical Guide
Dual Digital Module
11
Sequence of Operation
NOTE: See Unit Confi gurations Chart on page 10 for more
information about compressor staging.
Off Mode
The Dual Digital Module will be in the Off Mode when no signal is
being received from the VCM-X Modular series controller to run the
compressors.
Cooling Mode
When a Cool Signal is received, the Dual Digital Module will go into
Cooling Mode. At this point, Compressor A1 will energize and modulate
as necessary to maintain the Supply Air Temperature at the Active Supply
Air Setpoint that is broadcast from the VCM-X Modular series controller.
When Compressor A1 reaches 100%, a stage up timer is started. If
Compressor A1 stays at 100% for the stage up timer, Compressor B1
will energize and both compressors will go to 50% and begin to modu-
late together.
If there are additional fi xed compressor stages and modulating Com-
pressors A1 and B1 have modulated together up to 100%, then after a
stage up delay, fi xed Compressor A2 will stage on while A1/B1 go to
50% and begin to modulate from there. If A1/B1 again modulate up to
100%, then after a stage up delay, fi xed compressor B2 will stage on
while A1/B1 go to 50% and begin to modulate from there.
Staging down will happen in the reverse order as just described if the
Supply Air Temperature falls below the Supply Air Temperature Set-
point by the Cooling Stage Window value and the stage down timer
has elapsed. After the fi xed compressors have staged off, or if there are
no fi xed compressors, then the staging down of the digital compressors
A1 and B1 will continue as follows. If Compressors A1/B1 modulate
together down to 30% and the stage down timer elapses, Compressor B1
will deactivate and Compressors A1 will go to 60%. Compressors A1
will stage down if it is at 0% for the duration of the stage down timer.
Heat Pump Heating Mode (Air to Air)
Heating Mode works the same as Cooling Mode except the Reversing
Valve is switched and the sequence is opposite. Compressors modulate
up when below the Heating Supply Air Setpoint and modulate down
when above the setpoint.
Dehumidifi cation Mode
In Dehumidifi cation Mode, the compressor(s) will modulate to maintain
the Suction Pressure Temperature Setpoint broadcast from the VCM-X
Modular series controller. If there are two compressors, Compressor A1
will modulate up to 100% before Compressor B1 can be energized. If
Compressor B1 is energized, Compressor A1 will be locked at 100%.
If there are additional fi xed compressor stages and Compressor B1 has
modulated up to 100%, then after a stage up delay, fi xed Compressor
A2 will stage on while B1 will again go to 50% and begin to modulate
from there. If B1 again modulates up to 100%, then after a stage up
delay, fi xed compressor B2 will stage on while B1 will again go to 50%
and begin to modulate from there.
Stage down will again be the reverse as just described with Compressor
A1 being the last compressor to stage off.
Defrost Mode
In Defrost Mode, if only Circuit A is energized, it will go to 100% and
the reversing valve will deactivate. If both Circuit A & Circuit B are
energized, they will both go to 100% and the reversing valve will be
deactivated. The duration for Defrost Mode is determined by the VCM-X
Modular series controller.
NOTE: Defrost Mode is only available if a Two Condenser Head
Pressure Module is installed.
Staging Delays
Staging Delays minimum run times and minimum off times are sent
from the VCM-X Modular series controller.
Revised: 12/16/13