Orion System Two Condenser Head Pressure Module - Manual (Page 12)

Two Condenser Head Pressure Module
Technical Guide 12
Sequence of Operation
Input Commands (VCM-X Connection)
Condenser On/Off
Instead of a hard wired input signal to the Condenser Enable input,
the VCM-X Modular or VCM-X WSHP Controller communicates
to the Module via E-BUS communications. This signal indicates the
compressor(s) are called to run and drives the condenser A & B On/
Off function.
Cooling Enable On/Off
As with the Condenser Signal On/Off function, the VCM-X Modular
or VCM-X WSHP Controller communicates to the Module via E-BUS
communications and signals that the reversing valve has been energized
and that cooling has been enabled.
NOTE: When the term “ON” is used, it means there is either 24
VAC on the appropriate Binary Input or a call-to-run
signal is being received from a VCM-X series controller.
When the term “OFF” is used, it means there is either 0
VAC on the appropriate Binary Input or the call-to-run
signal from a VCM-X series controller has been removed.
Sensor Reading Routine
The Two Condenser Head Pressure Module is used on units with two
physically separate condenser sections. Up to two Head Pressure Sensors
can be monitored in each section. The highest of the two readings in each
section will be used to control the condenser fan(s) in that section.
Air from the condenser fan(s) in each section fl ows through both con-
denser coils. As a result, if you modulate the fan(s) based on the highest
reading, you will have enough air fl ow for both coils.
The highest reading of Head Pressure Sensors 1 & 2 controls Condenser
Fan A. The highest reading of Head Pressure Sensors 3 & 4 controls
Condenser Fan B.
Modes of Operation
OFF Mode
The Head Pressure Control Board is in the OFF Mode when the Con-
denser Input Signal is “OFF”. In this mode, all relays are off, the Analog
Output is 0 VDC, and the PWM Output is 0% Duty Cycle.
Cooling Mode
The Head Pressure Control board is in the Cooling Mode when the
Condenser Input Signal is “ON” and the Cooling Enable signal is “ON”.
The Condenser Enable Relays will energize to enable the Condenser
Fans or Water Valves, and the Cool Enable Relays will energize. In a
water system, the Water Flow Valve will start at 75% for 3 minutes. In
an air system, the Condenser Signal will go to 50% for 30 seconds. The
Condenser Output Signals will then automatically adjust between 0 and
100% to maintain the desired Head Pressure Setpoint. The Condenser
Output Signals can be a 0-10 VDC, 2-10 VDC or 0-100% PWM signal
provided by the appropriate output. Both outputs mirror each other.
NOTE: The Cooling enable outputs are for indication only and
are not wired to anything.
Heat Pump Mode
The Head Pressure Control Module is in the Heat Pump Mode when
the Condenser Input Signal is “ON” and the Cooling Enable signal is
“OFF”. In this mode, the Condenser Output Signals will go to 100%
and remain there until the unit leaves this mode.