Orion System SA E-BUS Controller - Manual (Page 43)

SA E-BUS Controller Technical Guide
Sequence of Operations
43
Cooling Mode
Units with 2 Digital Compressors and 2 ON/
OFF Compressors (Dual Unit)
The Compressors will Stage Up and Stage Down similar to 1 Digital
Compressor and 1 ON/OFF Compressor. The two Digital Compressors
modulate together as Stage One. The two ON/OFF Compressors are
considered the 2nd and 3rd Stage of Cooling.
The fi rst Stage ( 2 Digital Compressors) will modulate up. If the First
Stage stays at 100% for the Stage Up Delay and the Supply Air Tem-
perature is above the Supply Air Temperature Setpoint, then the Second
Stage will activate while the First Stage is allowed to modulate. This
sequence will repeat for the Third Cooling Stage.
If the two Digital Compressors fall below 20% and remain there for the
Stage Down Delay and the Supply Air Temperature is below the Supply
Air Temperature Setpoint minus the Cooling Stage Control Window,
then the Second Stage will deactivate. This sequence will repeat for the
Third Cooling Stage.
Air Cooled Condenser Fan Operation
If this is an Air Cooled SA Unit that has an installed Two Condenser
Head Pressure Module, whenever the compressor(s) are fi rst activated
the signal to the condenser fan will go to 50% for 30 seconds. After
this 30 second period, the unit will then monitor the Head Pressure
Transducer(s) and modulate the Condenser Fan(s) to maintain the Head
Pressure Setpoint (275 psi adjustable). The SA E-BUS Controller can
monitor up to two Head Pressure Transducers on a Single SA Unit or
up to two Head Pressure Transducers in each unit of a Dual SA Unit.
The highest of the two readings in each unit will be used to control the
Condenser Fan in that unit.
During Heat Pump Defrost, the Condenser Fan signal will go to 0%.
When compressors are not active the Condenser Fan signal will go to
100%.
Water Side Economizer Operation
(Valves 1 & 2)
The Water Side Economizer (WSE) is only available if using a Water
Cooled Condenser. The WSE is only active in the Cooling Mode and is
activated when the Entering Water Temperature drops 10°F (Adjustable)
below the Entering Air Temperature.
If the Compressors are Active:
The WSE (Valve 1) will open to 100% and the WSE Bypass (Valve
2) will close to 0%.
If the Compressors are not Active:
If the unit is confi gured for Constant Flow, the WSE (Valve 1) will
modulate to maintain the
Active Supply Air Cooling Temperature
Setpoint and the WSE Bypass (Valve 2) will modulate opposite.
If the unit is confi gured for Variable Flow, the WSE (Valve 1) will
modulate to maintain the
Active Supply Air Cooling Temperature
Setpoint and the WSE Bypass (Valve 2) will close.
The Economizer Deactivates as follows:
When the Entering Water Temperature rises to 8°F below the Enter-
ing Air Temperature, the WSE will deactivate.
If the unit is confi gured for Constant Flow, the WSE (Valve 1)
will close to 0% and the Economizer Bypass (Valve 2) will open
to 100%.
If the unit is confi gured for Variable Flow, the WSE (Valve 1)
will close to 0% and the WSE Bypass (Valve 2) will modulate to
maintain Head Pressure (275 psi adjustable). A Two Condenser
Head Pressure Module is required.
Water Cooled Condenser (Valve 3)
If the SA Unit has a Water Cooled Condenser and an installed Two Con-
denser Head Pressure Module, the SA E-BUS Controller can monitor
up to two Head Pressure Transducers on a Single SA Unit or up to two
Head Pressure Transducers in each unit of a Dual SA Unit. The highest
of the two readings in each unit will be used to control the Condenser
Valve in that unit.
If the unit is confi gured for Constant Flow:
When the compressor(s) are fi rst called to activate for Cooling,
Dehumidifi cation, or Heat Pump Heating Mode, the signal to the
condenser valve will go to 75% for 3 minutes in order to prove water
fl ow. After this 3 minute period, the compressor(s) will energize and
the Condenser Valve will modulate to maintain the Head Pressure
Setpoint (275 PSI adjustable).
During Heat Pump Heating, the Condenser Valve signal will go
to 100%. When compressors are not active, the Condenser Valve
signal will go to 100%.
Once Water Flow has been initially proven, the compressors are
energized for Cooling, Dehumidifi cation, or Heat Pump Heating.
Once the compressor(s) are energized, the only time a loss of water
fl ow will be recognized during Cooling or Dehumidifi cation is if
the Condenser Valve is above 70%. If this happens, an alarm will
be generated and the compressors(s) will be de-energized. During
Heat Pump Heating, anytime there is a loss of water fl ow, an alarm
will be generated and the compressors(s) will be de-energized.
If the unit is confi gured for Variable Flow and has no
Water Side Economizer (WSE):
When compressor(s) are fi rst called to activate, the signal to the
Condenser Valve will go to 75% for 3 minutes in order to prove
water fl ow. After this 3 minute period, compressor(s) will energize
and the Condenser Valve will modulate to maintain the Head Pres-
sure Setpoint (275 PSI adjustable). During Heat Pump Heating,
the Condenser Valve signal will go to 100%.
Water Flow must always be initially proven for the compressors
to energize for Cooling, Dehumidifi cation, or Heat Pump Heating.
Once the compressor(s) are energized, the only time a loss of water
fl ow will be recognized during Cooling or Dehumidifi cation is if
the Condenser Valve is above 70%. If this happens, an alarm will
be generated and the compressors(s) will be de-energized. During
Heat Pump Heating, anytime there is a loss of water fl ow, an alarm
will be generated and the compressors(s) will be de-energized.
When compressors are not active, the Condenser Fan signal will
go to 0%.