Orion System RNE Modular Controller - Manual (Page 54)

Zone
Zone
SEQUENCE OF OPERATION
RNE Modular Controller Field Technical Guide 54
Cooling Options
There are 3 types of Cooling available. They are as follows:
• Half VFD Compressor(s) and Half Fixed
Compressor(s)
• Full VFD Compressors
• Modulating Chilled Water
Cooling Staging and the Stage Control Window
In the Cooling Mode, as the Supply Air Temperature rises above the
Active Supply Air Temperature Setpoint, Cooling will begin to modu-
late or to stage. Successive stages will stage up based on the Stage Up
Delay period. Cooling Stages will continue to run until the Supply Air
Temperature falls below the Active Supply Air Cooling Setpoint minus
the Cooling Stage Control Window. For example, if the Active Supply
Air Cooling Setpoint is 55° and the Cooling Stage Control Window is
5°, as the Supply Air Temperature falls below 50°, the Cooling Stages
will begin to stage off based on the Cooling Stage Down Delay period.
Cooling Staging Delays
Minimum Off Time
A Cooling Stage cannot be activated unless it has been off for this
amount of time.
Minimum Run Time
After a Cooling Stage has been activated, it must remain on for
this amount of time.
Staging Up Delay
After the fi rst Cooling Stage has been activated, this delay pre-
vents additional stages from activating too quickly before they are
needed to achieve the Active Supply Air Temperature Setpoint.
Staging Down Delay
After a Cooling Stage has met its Minimum Run Time and is not
needed, this delay prevents additional stages from deactivating too
quickly in case they are needed to maintain the Active Supply Air
Temperature Setpoint Temperature.
Modulating Chilled Water
The RNE Controller can modulate a Chilled Water Valve with a 0-10
VDC or 2-10 VDC signal. The valve will modulate to maintain the
Active Supply Air Cooling Setpoint and is subject to a Minimum Run
Time and Minimum Off Time.
Half VFD Compressor(s) and Half Fixed
Compressor(s)
The RNE Controller will initiate and stage compressors based on the
above Staging and Time Delay descriptions.
2 Compressor Units (RNE 55-105)
The VFD Compressor will modulate as needed to maintain the
Active Supply Air Cooling Setpoint. If the compressor signal
reaches 80%, the Stage Up Timer will begin. If the Stage Up De-
lay period elapses and the compressor signal is still above 80%,
the Fixed Compressor will stage on, and the VFD Compressor
signal will be cut to half of its current signal. The VFD Com-
pressor will then modulate as needed to maintain the Supply Air
Setpoint.
With both compressors on, if the VFD Compressor signal falls to
30% for the Stage Down Delay period, then the Fixed Compres-
sor will stage off. The VFD Compressor signal will then modu-
late as needed to maintain the Supply Air Setpoint. If the VFD
Compressor then reaches 0% for the Stage Down Delay period,
it will be deactivated.
4 Compressor Units (RNE 120-140)
The two VFD Compressors will both be driven out of one
Analog Output, although the compressor relays will be enabled
separately as needed. The 1
st VFD Compressor will modulate to
maintain the Active Supply Air Cooling Setpoint. If the compres-
sor signal reaches 80%, the Stage Up Timer will begin. If the
Stage Up Delay period elapses and the compressor signal is still
at or above 80%, the 2
nd VFD Compressor relay will be enabled.
The VFD Compressor signal will then be cut to half of its current
value, and both VFD Compressors will modulate together as
needed to maintain the Supply Air Setpoint.
If the VFD Compressor signal again reaches 80% and remains
there for the Stage Up Delay period, the 3
rd compressor (a fi xed
stage) will be enabled to run. The VFD Compressor signal will
be cut to half its current value and will then modulate as neces-
sary to maintain the Supply Air Setpoint. This will be repeated
for the 4
th compressor (the second fi xed stage).
If more than one compressor is active and the VFD Compressor
signal falls to 30% for the Stage Down Delay period, the last
compressor staged on will then stage off. The VFD Compressor
will then modulate as needed. This will repeat as compressors
stage off. If the last compressor remaining on then reaches 0%
for the Stage Down Delay period, it will be deactivated.
Full VFD Compressors
2 Compressor Units (RNE 55-105)
The 1 st VFD Compressor will be driven out of Analog Output
(AO) #1, and the 2 nd VFD Compressor will be driven out of
AO #2. The 1 st VFD Compressor will modulate to maintain the
Active Supply Air Cooling Setpoint. If the compressor signal
reaches 80%, the Stage Up Timer will begin. If the Stage Up De-
lay period elapses and the compressor signal is still at our above
80%, the 2
nd VFD compressor will be enabled. The signals to
both VFD Compressors will then go to half of the current value
of the 1
st VFD Compressor. Both VFD Compressors will then
modulate together as needed to maintain the Supply Air Setpoint.
With both compressors on, if the VFD Compressor signal falls
to 30% for the Stage Down Delay period, the 2
nd VFD Compres-
sor will stage off. The remaining VFD Compressor will then
modulate as needed to maintain the Supply Air Setpoint. If the
last compressor reaches 0% for the Stage Down Delay period, it
will be deactivated.
Cooling Mode