Ingersoll-Rand ReliaTel, Manual, Page: 161 / 176

RT-SVD03L-EN 161
Novar Controls
Sequence of Operation
Novar is a control system that is often interfaced with
ReliaTel
™ controls which allows others to take control
of our equipment. The Novar system includes, but is
not limited to, a control module EMT2024 or EMT3051,
a relay panel and various sensors such as discharge
and return.
The Novar system connects to our unit in the same
manner as a conventional thermostat. Other
modifications are also made that allows the Novar
system to take control of the economizer.
General
Novar control units use a hybrid ReliaTel ™ Novar
control scheme. The ReliaTel ™ system is controlled
using the RTRM thermostat inputs connected to a
Novar electronic thermostat controller that serves as a
master unit controller and BAS network
communication device.
In addition to basic thermostat operation control, a
Novar unit includes some additional relay connections
that provide master control of economizer operation.
Cooling with an Economizer
On a Novar controlled system the master controller
initiates control requests to the RTRM through its
indoor fan, cool, and heat command outputs and the
RTRM thermostat inputs.
The economizer control actuator ((E EC CA A)) is wired to a
D Da am mp pe err relay and a N Niig gh htt m mo od de e damper relay as
described in the economizer set-up section. To enter an
economizer-cooling only mode, the master controller
will energize its F
Fa an n (G) output activating the supply
fan and close the contacts on the D Da am mp pe err relay
allowing a valid signal from the mixed air sensor.
The unit will then modulate the outdoor air damper
open if the mixed air sensor reading is high compared
to the mixed air setpoint of 53° F. If the damper relay is
not energized when the supply fan is on the ECA will
maintain the outdoor air damper at default minimum
position.
When the Novar controller senses conditions that
require additional cooling greater than that provided
from economizing, it will energize its C
Co oo oll 1 1 (Y1)
output calling for compressor operation.
If additional cooling is required above that provided by
the first stage of compressors the second stage will be
activated by energizing the C
Co oo oll 2 2 (Y2) output.
Compressors will respond to these calls independent of
the position or status of the economizer, but they will
continue to adhere to minimum on, off, and inter-stage
timing.
N No otte e:: When compressors are activated and the indoor
coil begins to cool down the temperature of the
mixed air sensor may drop below the mixed air
setpoint causing the ECA to close the outdoor air
damper to minimum position.
Cooling without an Economizer
The Novar controller uses its zone temperature input
and setpoint input to determine when to initiate
requests for compressors or heat. Calls for cooling are
interpreted by the ReliaTel
™ controller as thermostat
requests. When the zone temperature is sufficiently
greater than the setpoint, the Novar will energize its
C
Co oo oll 1 1 (Y1) output to turn compressors on. It will also
close the contacts on its F Fa an n (G) output to call for the
supply fan to turn on.
The first compressor will energize after its minimum 3-
minute off time has expired. If additional cooling
capacity is required above that provided by the first
stage the second stage of compressors will be
activated by energizing the C
Co oo oll 2 2 (Y2) output.
Once the zone temperature falls below the setpoint
sufficiently the compressor and fan outputs on the
Novar controller will be deactivated and the RTRM will
respond appropriately and deactivate its respective
outputs. As with normal thermostat control the Supply
Fan will remain on for a period of 60 seconds after the
compressor output is de-energized for free cooling.
Economizer Set-up
The economizer function on a Novar controlled unit is
controlled more directly than in normal operation. The
economizer is wired with additional inputs from the
Novar controller to provide this control:
Manual Enthalpy Override
The economizer control actuator (ECA) is configured
for Novar operation by placing a 100K resistor across
the normally unused outdoor air temp input on the
ECA. This signals the economizer to enter manual
enthalpy override which enables economizer cooling
operation at all times regardless of outdoor or indoor
conditions.
Damper Relay
A relay output on the Novar controller is that signals a
relay placed in-line with the mixed air temperature
sensor. It is used to interrupt the mixed air sensor
signal to the ECA indicating when to modulate for
economizing or to go to minimum position. If an open
is detected on the mixed air temperature input the ECA
will hold the damper at minimum position.
Night Mode Damper Relay
A relay on the Novar controller is connected across the
remote minimum position potentiometer inputs (P and